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Foreword 04

Committees 06

Poster awards 07

Sponsors 08

Exhibitors 09

Speakers 14

Abstracts 29

4 | o c t o b e r 2 7 - 3 1 , 2 0 1 4 T N T 2 0 1 4 b a r c e l o n a ( s p a i n )

On behalf of the International, Local and Technical

Committees, we take great pleasure in welcoming

you to Barcelona (Spain) for the 15th “Trends in

NanoTechnology” International Conference

(TNT2014).

TNT2014 is being held in large part due to the

overwhelming success of earlier TNT

Nanotechnology Conferences.

This high-level scientific meeting series aims to

present a broad range of current research in

Nanoscience and Nanotechnology worldwide, as

well as initiatives such as MANA/NIMS, CIC

nanoGUNE, IBEC, DIPC, etc. TNT events have

demonstrated that they are particularly effective in

transmitting information and promoting interaction

and new contacts among workers in this field.

Furthermore, this event offers visitors, exhibitors

and sponsors an ideal opportunity to interact with

each other.

This year, a Graphene one-day Symposium will

again be organized within TNT2014 in collaboration

with ICN2 (Spain).

This Graphene Day will entail a plenary session

during the morning and the afternoon session will

be divided in track A (Graphene science driven

contributions & Graphene in Cataluña) and track B

(Graphene driven applications Keynotes).

One of the main objectives of the Trends in

Nanotechnology conference is to provide a

platform where young researchers can present

their latest work and also interact with high-level

scientists. For this purpose, the Organising

Committee provides every year around 40 travel

grants for students. In addition, this year, 7 awards

will be given to young PhD students for their

contributions presented at TNT. More than 40

senior scientists are involved in the selection

process. Grants and awards are funded by the TNT

Organisation in collaboration with private bodies

and several governmental/research institutions.

TNT is now one of the premier European conferences

devoted to nanoscale science and technology.

We are indebted to the following Scientific

Institutions, Companies and Government Agencies

for their financial support: Phantoms Foundation,

Donostia International Physics Center (DIPC),

Universidad Autónoma de Madrid (UAM), ICEX

España Exportación e Inversiones, NIMS

(Nanomaterials Laboratory) and MANA

(International Center for Materials and

Nanoarchitectonics), Institute for Bioengineering of

Catalonia (IBEC), Institut Català de Nanociencia I

Nanotecnologia (ICN2), Materials Physics Center

(CFM), FEI, European Physical Society (EPS),

DAYFISA and Viajes El Corte Inglés.

We would also like to thank the following

companies and institutions for their participation:

Institut Català de Nanociencia I Nanotecnología

(ICN2), Raith Nanofabrication, Keysight

Technologies, Scientec Ibérica, Oxford Instruments,

WITec, LOT-QuantumDesign, Alava Ingenieros, ICEX

España Exportación e Inversiones and Phantoms

Foundation.

In addition, thanks must be given to the staff of all

the organising institutions whose hard work has

helped planning this conference.

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T N T 2 0 1 4 b a r c e l o n a ( s p a i n ) o c t o b e r 2 7 - 3 1 , 2 0 1 4 | 5

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TNT2014 Committees

Organising Committee

Jose-Maria Alameda (Universidad de Oviedo, Spain)

Masakazu Aono (MANA, NIMS, Japan)

Robert Baptist (CEA / DRT / LETI, France)

Xavier Cartoixa (UAB, Spain)

Antonio Correia (Phantoms Foundation, Spain) –

Conference Chairman

Gianaurelio Cuniberti (TUD, Germany)

Pedro Echenique (DICP / UPV, Spain)

Jose Maria Gonzalez Calbet (UCM, Spain)

Uzi Landman (Georgia Tech, USA)

Jose Manuel Perlado Martin (IFN-ETSII / UPM, Spain)

Jose Maria Pitarke (CIC nanoGUNE Consolider, Spain)

Pablo Ordejon (ICN2, Spain)

Ron Reifenberger (Purdue University, USA)

Jose Rivas (Santiago de Compostela Univ., Spain)

Juan Jose Saenz (UAM, Spain)

Josep Samitier (IBEC - Universitat de Barcelona, Spain)

Frank Scheffold (University of Fribourg, Switzerland)

Didier Tonneau (CNRS-CINaM, France)

International Scientific

Committee

Masakazu Aono (MANA / NIMS, Japan)

Emilio Artacho (CIC nanoGUNE Consolider, Spain)

Andreas Berger (CIC nanoGUNE Consolider, Spain)

Fernando Briones (IMM / CSIC, Spain)

Remi Carminati (Ecole Centrale Paris, France)

Jose-Luis Costa Kramer (IMM / CSIC, Spain)

Antonio Garcia Martin (IMM / CSIC, Spain)

Raquel Gonzalez Arrabal (IFN-ETSII / UPM, Spain)

Pierre Legagneux (Thales, France)

Annick Loiseau (ONERA - CNRS, France)

Stephan Roche (ICN2, Spain)

Josep Samitier (IBEC - Universitat de Barcelona, Spain)

Technical Committee

Carmen Chacón Tomé (Phantoms Foundation, Spain)

Viviana Estêvão (Phantoms Foundation, Spain)

Maite Fernández Jiménez (Phantoms Foundation, Spain)

Paloma Garcia Escorial (Phantoms Foundation, Spain)

Pedro Garcia Mochales (UAM, Spain)

Adriana Gil (Spain)

Conchi Narros Hernández (Phantoms Foundation, Spain)

Joaquin Ramon-Laca (Phantoms Foundation, Spain)

Jose-Luis Roldan (Phantoms Foundation, Spain)


TNT2014 Poster awards

Funded by Award

European Physical Society 222200000 Euros0 Euros0 Euros0 Euros

Phantoms Foundation TabletTabletTabletTablet



David Prize Private donation 300 US Dollars300 US Dollars300 US Dollars300 US Dollars

Keren Prize Private donation 300 US Dollars300 US Dollars300 US Dollars300 US Dollars

TNT 2014 Organisation Free registration to the Free registration to the Free registration to the Free registration to the

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TNT2014 Sponsors


TNT2014 Exhibitors

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Raith is a leading precision technology solution provider

for nanofabrication, electron beam lithography, focused

ion beam fabrication, nanoengineering and reverse

engineering applications.

Customers include universities and other organizations

involved in various fields of nanotechnology research

and materials science – as well as industrial and medium

sized enterprises that use nanotechnology for specific

product applications or produce compound

semiconductors.

Founded in 1980 and headquartered in Dortmund,

Germany, Raith employs more than 200 people. The

company works as close as possible with customers in

the most important global markets through subsidiaries

in the Netherlands, the USA and in Asia and through an

extensive partner and service network.

Raith GmbH

Konrad-Adenauer-Allee 8

44263 Dortmund- Germany

Phone: +49 (0)231 / 95004 - 0

Fax: +49 (0)231 / 95004 - 460

Web: www.raith.com

ScienTec Ibérica, is the spanish branch of ScienTec

France, its mission is to serve and attend the Iberian

Nano-micro surface analysis market from its office in

Madrid.

Its field of activity is related to scientific research, R&D

and industrial metrology. In terms of product line, we

deal with atomic force microscopes, contact

profilometry, digital holography, interferometry,

nanoindentation, filmetrics and high aspect ratio

confocals.

ScienTec Ibérica accompanies you in your various

projects by offering system adapted to your applications

(nanotechnology, polymer, material surfaces, biology,

semiconductor, microfabricaiton and the cutting tool

industry…)

ScienTec Ibérica

C/ Rufino Sánchez 83

28290 Las Rozas (Madrid)

Phone: 91-8429467

Fax: 902-875572

[email protected]

Web: www.scientec.es

The Institut Català de Nanociència i Nanotecnologia (ICN2)

focuses on the newly discovered physical and chemical

properties that arise from the fascinating behaviour of

matter at the nanoscale. The Mission of ICN2 is to achieve

scientific and technological excellence in nanoscience and

nanotechnology, and to facilitate the adoption and

integration of nanotechnologies into society and industry.

The patrons of ICN2 are the Government of Catalonia

(Generalitat), the Consejo Superior de Investigaciones

Científicas (CSIC), and the Autonomous University of

Barcelona (UAB). The Institute promotes collaboration

among scientists from diverse backgrounds (physics,

chemistry, biology, and engineering) to develop basic and

applied research, always seeking interactions with local and

global industry. ICN2 also trains researchers in

nanotechnology, develops numerous activities to facilitate

the uptake of nanotechnology by industry, and promotes

networking among scientists, engineers, technicians,

business people, society, and policy makers.

ICN2 was accredited in 2014 by the Spanish Ministry of

Economy and Competitiveness as a Severo Ochoa Centre

of Excellence, the highest recognition of centres of

excellence in Spain. The ICN2 proposal for this call focused

on the development of nanoscale devices that are effective

and marketable. Based on scientific advances in the

development of materials, nanofabrication,

characterisation, and theoretical simulation, practical

applications will be developed in three main areas:

Biosystems, Energy, and Information technology and

telecommunications.

Web: www.icn.cat

Keysight Technolgies (formerly Agilent Technologies) is

your one-stop shop for your research instrumentation.

We will show the new 7500 AFM which features atomic

resolution imaging with a 90um closed-loop scanner ,

the industry’s leading built in environmental chamber

and exceptional temperature control. Keysight will

introduce the 8500B FE SEM, a compact, high

performance SEM now with the option of EDS elemental

analysis. Combining low voltage imaging & advanced EDS

elemental analysis, the 8500B is the perfect lab

companion. Whatever your application we have the

instrument you need for your research.

Keysight Technologies

Web:www.keysight.com


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WITec GmbH is a manufacturer of high-resolution

optical and scanning probe microscopy solutions for

scientific and industrial applications:

• Scanning Near-field optical Microscopy (SNOM or

NSOM)

• Atomic Force Microscopy (AFM)

• Confocal Microscopy

• Raman Microscopy (Ultrasensitive and fast Raman

Imaging)

Focusing on innovations and constantly introducing new

technologies, we are the leading experts for your optical,

structural and chemical imaging tasks.

WITec GmbH (Headquarters)

Lise-Meitner-Str. 6

89081 Ulm, Germany

Tel: +49 (0)731 14070-0

Fax: +49 (0)731 14070-200

Web: www.WITec.de

LOT-QuantumDesign specialises in supplying high-

quality components and leading edge instrumentation to

the academic community and R&D market. LOT-

QuantumDesign staff have expertise in applications in

materials characterization, thin film analysis, special

cameras and imaging, spectroscopy, photonics and bio-

and nanotechnology. A dedicated team of more than

120 people in over 10 countries, supported by state of

the art infrastructure, provides fast, flexible and reliable

service to customers and partners.

At this exhibition LOT-QuantumDesign focuses on

displaying products from the branch of magnetism and

cryotechnology, including Quantum Designs PPMS and

MPMS, and a closed-cycle optical cryostats from

Montana Instruments, called the Cryostation. We will

also be happy to establish a contact to our other product

specialists, who are responsible for the above mentioned

application areas.

Web: www.lot-qd.com

Alava Ingenieros Group is an entirely privately owned

group which has been providing high technology

solutions in the Testing, Measurement, Communications,

Security, Defence and Preventive Maintenance fields

since it was first founded in 1973 and recently in

Nanotechnology.

The equipments that are provided from The

Nanotechnology Systems Division of Alava Ingenieros are

the following:

• LVEM5 (Delong America), the only benchtop

electron microscope with SEM, STEM and TEM

capabilities.

• 85000 FE-SEM (Keysight) a compact system that

offers researchers a field emission scanning

electron microscope right in their own laboratory.

• S neox (Sensofar), the non-contact optical 3D

profiling. S neox outperforms all existing optical

profilers, combining confocal, interferometry and

focus variation techniques in the same sensor head

without any moving parts.

• 5500 & 7500 AFM (Keysight), wide range of high-

precision atomic force microscopes that are highly

configurable.

• NanoIR (Anays Instruments), this tool reveals the

chemical composition of samples at the nanoscale

combining both nanoscale IR spectroscopy and

atomic force microscopy. In addition, the nanoIR

system provides high-resolution characterization of

local topographic, mechanical, and thermal

properties.

• G200 NanoIndenter (Keysight), the most accurate,

flexible, user-friendly instrument for

nanomechanical testing.

• Glovebox Workstations (MBraun) that can be

equipped with a comprehensive set of optional

features for the research and development of

emerging technologies, like PVD or ALD.

The group not only offers high technology distribution

but also consultancy, engineering, training and technical

services, providing turn-key projects. Alava Ingenieros

excels in its ability to adapt to the specific needs of its

customers and its responsible attitude towards supplies

and services carried out, all of which is backed by solid

international partnerships and in house resources for

integration, installation and after-sales technical service.

Web: www.alavaingenieros.com


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Omicron NanoScience is the world's leading supplier of

analytical instrumentation solutions in nanotechnology

research and development. With a team of more than

300 specialists we provide for:

• Cryogenic Systems (e.g. Optical & Spectroscopy

Cryostats, Helium-3 & Dilution refrigerators)

• Electron Spectroscopy (e.g. XPS systems,

Spectrometers, LEED, PEEM instruments)

• Scanning Probe Microscopy (e.g. our SPM’s for

Low-, Room-, and Variable Temperature)

• Superconducting Magnets (e.g. Superconducting

Solenoids, Ultra-High-Field-, Vector-rotate or

custom magnets, Magneto-optical systems)

• Thin Film & Tailored Systems (e.g. our MBE series

PRO, EVO and Lab)

• Service & Engineering

Oxford Instruments Omicron NanoScience

Limburger Str. 75

D-65232 Taunusstein, Germany

Tel: +49(0) 6128 / 987 – 0

Fax: +49(0) 6128 / 987 – 185

[email protected]

Web: www.oxford-instruments.com

ICEX Spain Trade and Investment is the Spanish

Government Agency serving Spanish companies to

promote their exports and facilitate their international

expansion, assisted by the network of Spanish Embassy’s

Economic and Commercial Offices.

Web: www.icex.es

Phantoms Foundation, based in Madrid, is a non-profit

organization which focus its activities on Nanoscience &

Nanotechnology (N&N), bringing together and

coordinating the efforts of Spanish and European

universities groups, research institutes and companies

through the organization of major scientific and

technological networks and events, such as ImagineNano

or Graphene. Today, the Phantoms Foundation is a key

player in structuring and promoting European excellence

and improving collaborations in N&N. It is also essential as

a platform for spreading excellence on funded projects

and for establishing new networks of collaboration.

Web: www.phantomsnet.net

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March 10-13Bilbao (Spain)

Graphene2014Short facts

5th edition


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page Masashi Aono (Tokyo Institute of Technology, Japan) “Amoeba-inspired Nanoarchitectonic Computing for Solving Computationally Demanding Problems”

Keynote Plenary Session

31 Adrian Bachtold (ICFO, Spain) “Mechanical resonators based on nanotubes and graphene”

Keynote Plenary Session 33

Elena Bailo (WITec GmbH, Germany) “Visualizing Carbon Material Properties at Highest Performance and Resolution Using Confocal Raman, AFM, SNOM and SEM”

Oral Senior Parallel Session Graphene-Industry 34

Lluís Balcells (ICAMB-CSIC, Spain) “Unexpected high conductivity at twin boundaries in LSMO thin films”

Oral Senior Plenary Session 36

Jose Eduardo Barrios-Vargas (ICN2, Spain) “Polycrystalline graphene as a raw material for gas sensors”

Oral Senior Parallel Session

Graphene in Cataluña 37 Wolfgang Belzig (University of Konstanz, Germany) “Ground state cooling of a carbon nano-mechanical resonator using spin-polarized current”

Oral Senior Plenary Session

39 Dario Bercioux (DIPC, Spain) “Pseudo-spin-dependent scattering in carbon nanotubes”

Invited Plenary Session 41

Xavier Blase (Institut Néel, CNRS & UFJ, France) “Excited states in organic systems from many-body-perturbation theory: the FIESTA initiative”


42 Mads Brandbyge (Technical University of Denmark, Denmark) “Elastic and inelastic electron transport simulations from first principles - new methods and effects”


43 Annalisa Calò (ICN2, Spain) “Water footprints in tip-sample force reconstruction for dynamic atomic force microscopy in ambient conditions”


44 Xavier Cartoixà (Universitat Autònoma de Barcelona, Spain) “Contact resistance in metal/two-dimensional material junctions from first principles”


Graphene in Cataluña 45 Nieves Casañ-Pastor (Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain) “Electrochemical production of graphene and of Carbon nanotubes or Graphene hybrids with Iridium Oxide. Coatings and electrodes for the Neural System”


47 Carlos Couso (Universitat Autonoma de Barcelona, Spain) “Simulation of CAFM topography and current of structures based in high-k dielectrics and graphene”

Oral PhD Parallel session

48

Gianaurelio Cuniberti (University of Technology Dresden, Germany) “Multiscale modelling in Advanced Materials and Devices”

Keynote Severo Ochoa

Session - Maria Luisa Della Rocca (Université Paris Diderot, France) “Quantum interference effect in anthraquinone solid-state junctions”


Index alphabetical order


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page Neus Domingo Marimon (ICN2 & CSIC, Spain) “Scanning probe piezoresistance: a new experimental tool (or what happens when you put an elephant on stilettos)”


53 Erik Dujardin (CEMES/CNRS, France) “Graphene as an integrated platform for molecular-scale devices”


Cesar Elosua (Public University of Navarre, Spain) “Optimization of an Optical Fiber Oxygen Sensor based on Metalloporphyrins Following Layer-by-Layer method”


55 Jordi Esquena (IQAC - CSIC, Spain) “Porous silica with complex dual morphology, prepared with a novel silica precursor in highly concentrated emulsions”


57 Ruben Esteban (DIPC, Spain) “Optoelectronics in plasmonic nanogaps”

Invited Plenary Session 58

Vladimir I. Fal'ko (Lancaster University, UK) “Anomalous sequence of quantum Hall liquids revealing tunable Lifshitz transition in bilayer graphene”


59 Joaquín Fernández-Rossier (INL, Portugal) “Designer nanomagnets”


Nuria Ferrer-Anglada (Universitat Politècnica de Catalunya, Spain) “Stable p-doping in graphene and Terahertz spectroscopy”

Invited Parallel Session

Graphene in Cataluña 61 Mikhail Fistul (Ruhr-Universität Bochum, Germany) “Radiation-induced coherent quantum phenomena in the transport of graphene based n-p and n-p-n junctions”


62 Alicia Forment-Aliaga (ICMOL-Universidad de València, Spain) “Magnetic Imaging and Manipulation of Molecular-based Nanoparticles”

Oral Senior Parallel Session 64

Arantxa Fraile Rodríguez (Universitat de Barcelona, Spain) “Direct imaging of tunable exchange bias domains in model Ni/FeF2 nanostructures”


65 Giancarlo Franzese (Universitat de Barcelona, Spain) “The nanoparticles protein corona: How to extract a predictive molecular model from the experiments”


67 Laura Fumagalli (IBEC, Spain) “Probing electric polarization of nano-objects and biomolecules using scanning probe microscopy”


68 Andreas Gang (TU Dresden, Germany) “Silicon nanowire based (bio) sensing”

Oral PhD Parallel session 69

Gastón García (ALBA-CELLS, Spain) “The ALBA synchrotron light source: a tool for nanoscience”


Maia Garcia Vergniory (Donostia International Physics Center, Spain) “Magnetic interaction and magnetic fluctuations in topological insulators with ordered and disordered magnetic adatoms”


71 Jose A. Garrido (Technische Universität München, Germany) “Graphene field effect transistors for biosensing and bioelectronics”


Luca Gavioli (Università Cattolica del Sacro Cuore di Brescia, Italy) “Highly bactericidal Ag nanoparticle films obtained by cluster beam deposition”


Philippe Godignon (CNM-ICMAB-CSIC, Spain) “Challenges in nano-patterning of epitaxial graphene grown on Silicon Carbide wafers”


Graphene in Cataluña 76


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Invited Severo Ochoa

Session 185 Gonçalo Gonçalves (Aixtron Ltd., UK) “Recent advances in CVD graphene”

Keynote Parallel Session

Graphene/Industry 78 Alexander Govyadinov (CIC nanoGUNE, Spain) “Recovery of Permittivity and Depth from Near-Field Data as a Step toward Infrared Nanotomography”


79 Benjamin Grevin (CEA-CNRS-UJF, France) “High resolution non-contact AFM and Kelvin Probe Force Microscopy investigations of self-organized photovoltaic organic architectures”


81 Konstantin Gusliyenko (UPV/EHU & IKERBASQUE, Spain) “Microwave absorption properties of two dimensional arrays of permalloy nanodots in the vortex and quasi-uniform ground states”


83 Kelli Hanschmidt (Univesity of Tartu, Estonia) “Metal oxide fibers or micropipe preparation exploitation improving mechanism of metal alkoxide liquid threads”


85 Kazutoshi Haraguchi (Nihon Unviersity, Japan) “Synthesis and functions of platinum-polymer-clay nanocomposite gels fabricated via exfoliated clay-mediated in situ reduction”

Invited Plenary Session

87 Josef Havel (Masaryk University, Czech Republic) “Chalcogenide glasses – advanced nano-materials with still not completely resolved structure. Laser desorption ionization and mass spectrometry of clusters generated in gas phase for structure elucidation”


89 Alejandro Hernández Albors (IQAC- CSIC, Spain) “Development of a Columbimetric Immunosensor for the Detection of Human Cardiac Troponin I”


91 Rainer Hillenbrand (CIC nanoGUNE, Spain) “Two-Dimensional Optics with Graphene Plasmons Launched by Metal Antennas”


Imad Ibrahim (IFW-Dresden , Germany) “Growth of semiconducting enriched SWCNT on ST-cut quartz substrate by chemical vapor deposition”


94 Wlodzimierz Jaskólski (Nicolaus Copernicus University, Poland) “Theory of the electronic structure of grain boundaries in graphene”



David Jiménez (Universitat Autònoma de Barcelona, Spain) “Detrimental factors lowering the performance of graphene field-effect transistors”


Graphene in Cataluña 98 Esteve Juanola-Feliu (University of Barcelona, Spain) “Design of a multipurpose nano-enabled implantable device for personalized medicine”


100 Gerald Kada (Keysight Technologies, Austria) “Simultaneous Topography and Electrochemical Imaging (SECM)”


Alekber Kasumov (LPS, Universite Paris-Sud, France) “Bismuth nanowires based Josephson junctions in very high magnetic fields”


Ladislav Kavan (J. Heyrovský Institute of Physical Chemistry, Czech Republic) “Nanocrystalline Boron-doped Diamond: Spectro /Photo /Electrochemical Properties and Prospective Applications in Solar Cells”


106 Frank Koppens (ICFO, Spain) “Electrical control and detection of nanoscale optical fields with 2d materials”



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page Kostas Kostarelos (University of Manchester, UK) “Adoption of graphene materials in medicine”


Boris Kulnitskiy (TISNCM, Russia) “Unusual boron distribution in as-grown boron-doped diamond”


Uzi Landman (Georgia Tech, USA) “Adventures in Nanoscale Computational Microscopy”

Keynote Plenary Session -

Laura M. Lechuga (ICN2 & CSIC, Spain) “Nanophotonic lab-on-chip biosensors for point-of-care diagnostics”


Nicolas Leconte (ICN2, Spain) “Quantum transport in chemically functionalized graphene at high magnetic field: Defect-Induced Critical States and Breakdown of Electron-Hole Symmetry”


Graphene in Cataluña 113 Max Lemme (University of Siegen, Germany) “Graphene in Microelectronics - It's not all about Mobility!”


Graphene/Industry 114 Mathias P. Ljungberg (DIPC, Spain) “Optical spectra and quasiparticle energies of molecules using a local basis”


Aitor Lopeandia (Universitat Autònoma de Barcelona, Spain) “CMOS compatible µ-TEG based on single crystalline Si thin films”


Markus Maier (Omicron NanoTechnology GmbH, Germany) “Recent Advancements in Surface Science Instrumentation - The LT Nanoprobe”


Lluis F. Marsal (Universitat Rovira i Virgili, Spain) “Nanostructural engineering of nanoporous anodic alumina for optical biosensing”


Jesús Martínez De La Fuente (ICMA, Instituto de Ciencias de Materiales de Aragón, Spain) “Designing inorganic nanoparticles for biotechnological applications”

Keynote Severo Ochoa

Session 120 Gema Martinez-Criado (ESRF, France) “Exploring Single Semiconductor Nanowires with a Multimodal Hard X-ray Nanoprobe”


122 Antonio J. Martínez-Galera (UAM, Spain & Universität zu Köln, Germany) “Graphene Nanopatterning at the Nanometer Scale”


Mathieu Massicotte (ICFO-Institut de Ciéncies Fotoniques, Spain) “Photocurrent spectroscopy in TMDC-based van der Waals heterostructures”


124

Arben Merkoçi (ICN2 & ICREA, Spain) “Graphene-based platforms for electrical and optical biosensing“



Arben Merkoçi (ICN2 & ICREA, Spain) “Biosensors“


Session - Francisco J. Meseguer (Universidad Politécnica de Valencia & ICMM-CSIC, Spain) “Silicon colloids. Properties and applications to metamaterials, sensing and solar energy harvesting”


126 Neeraj Mishra (Istituto Italiano di Tecnologia, Italy) “A study on the growth of graphene on h-BN by chemical vapor deposition”


Samindranath Mitra (Physical Review Letters, USA) “Graphene in PRL”


Manel Molina-Ruiz (Universitat Autònoma de Barcelona, Spain) “Microsecond-pulse heating nanocalorimetry: quasi-static method”



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page Cesar Moreno (ICN2, Spain & ICYS-NIMS, Japan) “Three-dimensional imaging with submolecular resolution by atomic force microscopy”


130 Carlos Moya (Universitat de Barcelona, Spain) “Spin configurations of individual Fe3-xO4 nanoparticles”


Enrique Navarro (Pyrenean Institute of Ecology (CSIC), Spain) “Assessing the environmental toxicity of nanomaterials: the case of silver nanoparticles”


132 Peter Nirmalraj (IBM Research - Zurich, Switzerland) “Imaging molecular and atomic-scale materials in high density liquids”


Bernat Olivera (Universidad de Alicante, Spain) “Kondo Physics in 4f metals: Gadolinium nanocontacts”


Florian Otto (attocube systems AG, Germany) “Sensitive scanning probe microscopy performed in an ultra-low vibration closed-cycle cryostat down to 1.5 K”


135 Cristina Paez-Aviles (SIC-BIO, University of Barcelona, Spain) “Nanobiotechnology and Nanomedicine: Innovation and market Challenges towards H2020. A multi-KET approach”


136 Lionel Patrone (IM2NP CNRS, France) “Impact of π-conjugated self-assembled monolayer structure on their electrical properties”


138 Michael D. Patterson (Graphene Frontiers, USA) “Graphene Biosensors – The Next Frontier in Medical Diagnostics”


Graphene/Industry 140 Vladimir Popov (NUST “MISIS”, Russia) “Investigation of non-agglomerated nanodiamonds inside aluminum matrix composites produced by mechanical alloying”


141 Elisabet Prats-Alfonso (IMB-CNM (CSIC) & CIBER-BBN, Spain) “Validation of graphene-based devices for neurophysiological recordings”


Graphene/Industry 144 Helena Prima-Garcia (ICMOL, Universidad de Valencia, Spain) “Hybrid Materials for Molecular Spintronics: Fabrication of spin-OLEDs”


Valerio Pruneri (ICFO, Spain) “Ultrathin metals and graphene for flexible optoelectronic devices”


Graphene in Cataluña 147 Romain Quidant (ICFO & ICREA, Spain) “Thermoplasmonics: Nanoscale control of heat and its applications”


Raúl Rengel (Universidad de Salamanca, Spain) “Impact of the Temperature and Remote Phonon Scattering on Charge Transport in Supported Graphene”


Graphene in Cataluña 149 Felix Ritort (Universitat de Barcelona & CIBER-BBN, Spain) “Force spectroscopy of anticancer drugs binding nucleic acids”


Stephan Roche (ICN2 & ICREA, Spain) “Theory”


Session 152 Lucía Rodrigo (Universidad Autónoma de Madrid, Spain) “Sublattice localized electronic states in atomically resolved graphene-Pt(111) edge-boundaries”


153 Günther Ruhl (Infineon Technologies AG, Germany) “Perspectives of Graphene in Semiconductor Industry”


Graphene/Industry 154


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Mark H. Rümmeli (Sungkyunkwan Univ. & Center for Integrated Nanostructure Physics (IBS), South Korea) “Room temperature in-situ nanostructure synthesis using electron beam irradiation”


156 Riccardo Rurali (ICMAB-CSIC, Spain) “Heat transport across a SiGe nanowire axial junction: interface thermal resistance and thermal rectification”


157

Saverio Russo (University of Exeter, United Kingdom) “Elucidating the limiting factor of the electrical properties of WS2 and MoS2”


159 Jose Sanchez Costa (LCC, CNRS, France) “Surface plasmons spectroscopy for monitoring the spin crossover phenomena at the nanometric scale”


160 Rubén Sánchez-Hidalgo (University of Salamanca, Spain) “Graphene Oxide: the role of chemical composition on the properties of thin films”


Daniel Sánchez-Portal (CFM-UPV/EHU & DIPC, Spain) “Simulations of Electron Dynamics in Solids and Nanostructures with SIESTA”


Martin Schnell (CIC nanoGUNE, Spain) “Synthetic Optical Holography for Rapid Optical Nanoimaging”


Karlheinz Strobl (CVD Equipment Corporation, USA) “CVD graphene: Batch versus Roll to Roll Scale-up”


Graphene/Industry 166 Christoph Strunk (University of Regensburg, Germany) “Discrete symmetries and the Kondo Effect in Clean Carbon Nanotubes”


Sergio Tatay (Universitat de València, Spain) “Growth of Self-Assembled Monolayers directly on a ferromagnetic metal surface”


Kazuya Terabe (National Institute for Materials Science, Japan) “Functionality controls of metallic and graphene oxides based on solid-state-nanoionics”


170 Klaas-Jan Tielrooij (ICFO - Institut de Ciéncies Fotóniques, Spain) “Ultrafast and efficient photo-induced electron heating in graphene”


Sergio Valenzuela (ICN2 & ICREA, Spain) “ICT”


Session - Oriol Vilanova (Universitat de Barcelona, Spain) “Predicting the kinetics of Protein-Nanoparticle corona formation in a simplified plasma”


172 Peter Weber (ICFO - The Institute of Photonic Sciences, Spain) “Coupling Graphene Mechanical Resonators to Superconducting Microwave cavities”


173 Eva M. Weig (University of Konstanz, Germany) “Coherent control of nanoelectromechanical systems”


Achim Woessner (ICFO - The Institute of Photonic Sciences, Spain) “Highly confined low-loss plasmons in graphene-boron nitride heterostructures”


Qian Wu (Universitat Autònoma de Barcelona (UAB), Spain) “CAFM study of Negative Bias Temperature Instability and Channel hot-carriers degradation in strained and non-strained MOSFETs”


177 Chanyoung Yim (Trinity College Dublin, Ireland) “Investigation of Photodiodes from Vapor Phase Grown MoS2”



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page Hadi M. Zareie (Izmir Institute of Technology, Turkey & University of Technology Sydney, Australia) “Plasmonic Biosensors”


181 Marketa Zukalova (J. Heyrovsky Institute of Physical Chemistry, ASCR, Czech Republic) “Dense TiO2 Thin Layers Prepared by Sol-Gel for Dye Sensitized Solar Cells: Electrochemical Properties”


182 Amaia Zurutuza (Graphenea S. A., Spain) “Progress in Graphene Materials Applications”


Graphene/Industry 184

o c t o b e r 2 7 - 3 1 , 2 0 1 4 T N T 2 0 1 4 b a r c e l o n a ( s p a i n ) | 21

page Masashi Aono (Tokyo Institute of Technology, Japan) “Amoeba-inspired Nanoarchitectonic Computing for Solving Computationally Demanding Problems”

31 Adrian Bachtold (ICFO, Spain) “Mechanical resonators based on nanotubes and graphene”

33

Xavier Blase (Institut Néel, CNRS & UFJ, France) “Excited states in organic systems from many-body-perturbation theory: the FIESTA initiative”

42 Mads Brandbyge (Technical University of Denmark, Denmark) “Elastic and inelastic electron transport simulations from first principles - new methods and effects”

43 Erik Dujardin (CEMES/CNRS, France) “Graphene as an integrated platform for molecular-scale devices”

54

Joaquín Fernández-Rossier (INL, Portugal) “Designer nanomagnets”

60

Laura Fumagalli (IBEC, Spain) “Probing electric polarization of nano-objects and biomolecules using scanning probe microscopy”

68 Jose A. Garrido (Technische Universität München, Germany) “Graphene field effect transistors for biosensing and bioelectronics”

72

Gonçalo Gonçalves (Aixtron Ltd., UK) “Recent advances in CVD graphene”

78

Rainer Hillenbrand (CIC nanoGUNE, Spain) “Two-Dimensional Optics with Graphene Plasmons Launched by Metal Antennas”

93

Frank Koppens (ICFO, Spain) “Electrical control and detection of nanoscale optical fields with 2d materials”

107

Kostas Kostarelos (University of Manchester, UK) “Adoption of graphene materials in medicine”

108

Uzi Landman (Georgia Tech, USA) “Adventures in Nanoscale Computational Microscopy”

-

Laura M. Lechuga (INC2 & CSIC, Spain) “Nanophotonic lab-on-chip biosensors for point-of-care diagnostics”

111

Max Lemme (University of Siegen, Germany) “Graphene in Microelectronics - It's not all about Mobility!”

114

Markus Maier (Omicron NanoTechnology GmbH, Germany) “Recent Advancements in Surface Science Instrumentation - The LT Nanoprobe”

118

Lluis F. Marsal (Universitat Rovira i Virgili, Spain) “Nanostructural engineering of nanoporous anodic alumina for optical biosensing”

119

Keynotes


page Jesús Martínez De La Fuente (ICMA, Instituto de Ciencias de Materiales de Aragón, Spain) “Designing inorganic nanoparticles for biotechnological applications”

120

Francisco J. Meseguer (Universidad Politécnica de Valencia & ICMM-CSIC, Spain) “Silicon colloids. Properties and applications to metamaterials, sensing and solar energy harvesting”

126 Enrique Navarro (Pyrenean Institute of Ecology (CSIC), Spain) “Assessing the environmental toxicity of nanomaterials: the case of silver nanoparticles”

132

Michael D. Patterson (Graphene Frontiers, USA) “Graphene Biosensors – The Next Frontier in Medical Diagnostics”

140

Romain Quidant (ICFO & ICREA, Spain) “Thermoplasmonics: Nanoscale control of heat and its applications”

148

Felix Ritort (Universitat de Barcelona & CIBER-BBN, Spain) “Force spectroscopy of anticancer drugs binding nucleic acids”

151

Günther Ruhl (Infineon Technologies AG, Germany) “Perspectives of Graphene in Semiconductor Industry”

154

Daniel Ruiz-Molina (ICN2 & CSIC, Spain) “Catechol-based bioinspired materials: from theranostics to water treatment”

155

Mark H. Rümmeli (Sungkyunkwan Univ. & Center for Integrated Nanostructure Physics (IBS), South Korea) “Room temperature in-situ nanostructure synthesis using electron beam irradiation”

156 Daniel Sánchez-Portal (CFM-UPV/EHU & DIPC, Spain) “Simulations of Electron Dynamics in Solids and Nanostructures with SIESTA”

163

Karlheinz Strobl (CVD Equipment Corporation, USA) “CVD graphene: Batch versus Roll to Roll Scale-up”

166

Christoph Strunk (University of Regensburg, Germany) “Discrete symmetries and the Kondo Effect in Clean Carbon Nanotubes”

167

Kazuya Terabe (National Institute for Materials Science, Japan) “Functionality Controls of Metallic and Graphene Oxides Based on Solid-State-Nanoionics”

170

Eva M. Weig (University of Konstanz, Germany) “Coherent control of nanoelectromechanical systems”

174

Amaia Zurutuza (Graphenea S.A., Spain) “Progress in Graphene Materials Applications”

184


page Dario Bercioux (DIPC, Spain) “Pseudo-spin-dependent scattering in carbon nanotubes”

41

Ruben Esteban (DIPC, Spain) “Optoelectronics in plasmonic nanogaps”

58

Nuria Ferrer-Anglada (Universitat Politècnica de Catalunya, Spain) “Stable p-doping in graphene and Terahertz spectroscopy”

61

Philippe Godignon (CNM-ICMAB-CSIC, Spain) “Challenges in nano-patterning of epitaxial graphene grown on Silicon Carbide wafers”

76

Pedro Gómez-Romero (ICN2 & CSIC, Spain) “Energy Nanomaterials”

185

Kazutoshi Haraguchi (Nihon Unviersity, Japan) “Synthesis and functions of platinum-polymer-clay nanocomposite gels fabricated via exfoliated clay-mediated in situ reduction”

87 David Jiménez (Universitat Autònoma de Barcelona, Spain) “Detrimental factors lowering the performance of graphene field-effect transistors”

98

Arben Merkoçi (ICN2 & ICREA, Spain) “Graphene-based platforms for electrical and optical biosensing“

125

Arben Merkoçi (ICN2 & ICREA, Spain) “Biosensors“

-

Valerio Pruneri (ICFO, Spain) “Ultrathin metals and graphene for flexible optoelectronic devices”

147

Stephan Roche (ICN2 & ICREA, Spain) “Theory”

152

Sergio Valenzuela (ICN2 & ICREA, Spain) “ICT”

-

Invited


page Lluís Balcells (ICAMB-CSIC, Spain) “Unexpected high conductivity at twin boundaries in LSMO thin films”

36

Wolfgang Belzig (University of Konstanz, Germany) “Ground state cooling of a carbon nano-mechanical resonator using spin-polarized current”

39

Nieves Casañ-Pastor (Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain) “Electrochemical production of graphene and of Carbon nanotubes or Graphene hybrids with Iridium Oxide. Coatings and electrodes for the Neural System”

47 Maria Luisa Della Rocca (Université Paris Diderot, France) “Quantum interference effect in anthraquinone solid-state junctions”

51

Jordi Esquena (IQAC - CSIC, Spain) “Porous silica with complex dual morphology, prepared with a novel silica precursor in highly concentrated emulsions”

57 Vladimir I. Fal´ko (Lancaster University, UK) “Anomalous sequence of quantum Hall liquids revealing tunable Lifshitz transition in bilayer graphene”

59 Mikhail Fistul (Ruhr-Universität Bochum, Germany) “Radiation-induced coherent quantum phenomena in the transport of graphene based n-p and n-p-n junctions”

62 Maia Garcia Vergniory (Donostia International Physics Center, Spain) “Magnetic interaction and magnetic fluctuations in topological insulators with ordered and disordered magnetic adatoms”

71 Alexander Govyadinov (CIC nanoGUNE, Spain) “Recovery of Permittivity and Depth from Near-Field Data as a Step toward Infrared Nanotomography”

79

Benjamin Grevin (CEA-CNRS-UJF, France) “High resolution non-contact AFM and Kelvin Probe Force Microscopy investigations of self-organized photovoltaic organic architectures”

81 Konstantin Gusliyenko (UPV/EHU & IKERBASQUE, Spain) “Microwave absorption properties of two dimensional arrays of permalloy nanodots in the vortex and quasi-uniform ground states”

83 Ladislav Kavan (J. Heyrovský Institute of Physical Chemistry, Czech Republic) “Nanocrystalline Boron-doped Diamond: Spectro/Photo/Electrochemical Properties and Prospective Applications in Solar Cells”

106 Mathias P. Ljungberg (DIPC, Spain) “Optical spectra and quasiparticle energies of molecules using a local basis”

115

Gema Martinez-Criado (ESRF, France) “Exploring Single Semiconductor Nanowires with a Multimodal Hard X-ray Nanoprobe”

122

Antonio J. Martínez-Galera (UAM, Spain & Universität zu Köln, Germany) “Graphene Nanopatterning at the Nanometer Scale”

123

Neeraj Mishra (Istituto Italiano di Tecnologia, Italy) “A study on the growth of graphene on h-BN by chemical vapor deposition”

127

Orals - senior (plenary session)


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page Samindranath Mitra (Physical Review Letters, USA) “Graphene in PRL”

128

Cesar Moreno (ICN2, Spain & ICYS-NIMS, Japan) “Three-dimensional imaging with submolecular resolution by atomic force microscopy”

130

Peter Nirmalraj (IBM Research - Zürich, Switzerland) “Imaging molecular and atomic-scale materials in high density liquids”

133

Lionel Patrone (IM2NP CNRS, France) “Impact of π-conjugated self-assembled monolayer structure on their electrical properties”

138

Vladimir Popov (NUST “MISIS”, Russia) “Investigation of non-agglomerated nanodiamonds inside aluminum matrix composites produced by mechanical alloying”

141 Riccardo Rurali (ICMAB-CSIC, Spain) “Heat transport across a SiGe nanowire axial junction: interface thermal resistance and thermal rectification”

157 Saverio Russo (University of Exeter, UK) “Elucidating the limiting factor of the electrical properties of WS2 and MoS2”

159

Martin Schnell (CIC nanoGUNE, Spain) “Synthetic Optical Holography for Rapid Optical Nanoimaging”

165

Sergio Tatay (Universitat de València, Spain) “Growth of Self-Assembled Monolayers directly on a ferromagnetic metal surface”

168

Klaas-Jan Tielrooij (ICFO - Institut de Ciéncies Fotóniques, Spain) “Ultrafast and efficient photo-induced electron heating in graphene”

171

Hadi M. Zareie (Izmir Institute of Technology, Turkey & University of Technology Sydney, Australia) “Plasmonic Biosensors”

181


page Elena Bailo (WITec GmbH, Germany) “Visualizing Carbon Material Properties at Highest Performance and Resolution Using Confocal Raman, AFM, SNOM and SEM”

34 Jose Eduardo Barrios-Vargas (ICN2), Spain) “Polycrystalline graphene as a raw material for gas sensors”

37

Annalisa Calò (ICN2 & CSIC, Spain) “Water footprints in tip-sample force reconstruction for dynamic atomic force microscopy in ambient conditions”

44 Xavier Cartoixà (Universitat Autònoma de Barcelona, Spain) “Contact resistance in metal/two-dimensional material junctions from first principles”

45

Neus Domingo Marimon (ICN2, Spain) “Scanning probe piezoresistance: a new experimental tool (or what happens when you put an elephant on stilettos)”

53 Cesar Elosua (Public University of Navarre, Spain) “Optimization of an Optical Fiber Oxygen Sensor based on Metalloporphyrins Following Layer-by-Layer method”

55 Alicia Forment-Aliaga (ICMOL-Universidad de València, Spain) “Magnetic Imaging and Manipulation of Molecular-based Nanoparticles”

64

Arantxa Fraile Rodríguez (Universitat de Barcelona, Spain) “Direct imaging of tunable exchange bias domains in model Ni/FeF2 nanostructures”

65

Giancarlo Franzese (Universitat de Barcelona, Spain) “The nanoparticles protein corona: How to extract a predictive molecular model from the experiments”

67

Gastón García (ALBA-CELLS, Spain) “The ALBA synchrotron light source: a tool for nanoscience”

70

Luca Gavioli (Università Cattolica del Sacro Cuore di Brescia, Italy) “Highly bactericidal Ag nanoparticle films obtained by cluster beam deposition”

73

Josef Havel (Masaryk University, Czech Republic) “Chalcogenide glasses – advanced nano-materials with still not completely resolved structure. Laser desorption ionization and mass spectrometry of clusters generated in gas phase for structure elucidation”

89 Imad Ibrahim (IFW-Dresden , Germany) “Growth of semiconducting enriched SWCNT on ST-cut quartz substrate by chemical vapor deposition”

94

Wlodzimierz Jaskólski (Nicolaus Copernicus University, Poland) “Theory of the electronic structure of grain boundaries in graphene”

96

Esteve Juanola-Feliu (University of Barcelona, Spain) “Design of a multipurpose nano-enabled implantable device for personalized medicine”

100

Gerald Kada (Agilent Technologies/Keysight Technologies, Austria) “Simultaneous Topography and Electrochemical Imaging (SECM)”

102

Alekber Kasumov (LPS, U. Paris-Sud, France) “Bismuth nanowires based Josephson junctions in very high magnetic fields”

104

Oral - Seniors (parallel session)


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page Boris Kulnitskiy (TISNCM, Russia) “Unusual boron distribution in as-grown boron-doped diamond”

109

Nicolas Leconte (ICN2, Spain) “Quantum transport in chemically functionalized graphene at high magnetic field: Defect-Induced Critical States and Breakdown of Electron-Hole Symmetry”

113 Aitor Lopeandia (Universitat Autònoma de Barcelona, Spain) “CMOS compatible µ-TEG based on single crystalline Si thin films”

116

Florian Otto (attocube systems AG, Germany) “Sensitive scanning probe microscopy performed in an ultra-low vibration closed-cycle cryostat down to 1.5 K”

135 Elisabet Prats-Alfonso (IMB-CNM (CSIC) / CIBER-BBN, Spain) “Validation of graphene-based devices for neurophysiological recordings”

144

Helena Prima-Garcia (ICMOL, Universidad de Valencia, Spain) “Hybrid Materials for Molecular Spintronics: Fabrication of spin-OLEDs”

146

Raúl Rengel (Universidad de Salamanca, Spain) “Impact of the Temperature and Remote Phonon Scattering on Charge Transport in Supported Graphene”

149 Jose Sanchez Costa (LCC / CNRS, France) “Surface plasmons spectroscopy for monitoring the spin crossover phenomena at the nanometric scale”

160 Marketa Zukalova (J. Heyrovsky Institute of Physical Chemistry, ASCR, Czech Republic) “Dense TiO2 Thin Layers Prepared by Sol-Gel for Dye Sensitized Solar Cells: Electrochemical Properties”

182


page Carlos Couso (Universitat Autonoma de Barcelona, Spain) “Simulation of CAFM topography and current of structures based in high-k dielectrics and graphene”

48 Andreas Gang (TU Dresden, Germany) “Silicon nanowire based (bio) sensing”

69

Kelli Hanschmidt (Univesity of Tartu, Estonia) “Metal oxide fibers or micropipe preparation exploitation improving mechanism of metal alkoxide liquid threads”

85 Alejandro Hernández Albors (IQAC- CSIC & CIBER-BBN, Spain) “Development of a Columbimetric Immunosensor for the Detection of Human Cardiac Troponin I”

91 Mathieu Massicotte (ICFO-Institut de Ciéncies Fotoniques, Spain) “Photocurrent spectroscopy in TMDC-based van der Waals heterostructures”

124

Manel Molina-Ruiz (Universitat Autònoma de Barcelona, Spain) “Microsecond-pulse heating nanocalorimetry: quasi-static method”

129

Carlos Moya (Universitat de Barcelona, Spain) “Spin configurations of individual Fe3-xO4 nanoparticles”

131

Bernat Olivera (Universidad de Alicante, Spain) “Kondo Physics in 4f metals: Gadolinium nanocontacts”

134

Cristina Paez-Aviles (SIC-BIO, University of Barcelona, Spain) “Nanobiotechnology and Nanomedicine: Innovation and market Challenges towards H2020. A multi-KET approach”

136 Lucía Rodrigo (Universidad Autónoma de Madrid, Spain) “Sublattice localized electronic states in atomically resolved graphene-Pt(111) edge-boundaries”

153

Rubén Sánchez-Hidalgo (University of Salamanca, Spain) “Graphene Oxide: the role of chemical composition on the properties of thin films”

161

Oriol Vilanova (Universitat de Barcelona, Spain) “Predicting the kinetics of Protein-Nanoparticle corona formation in a simplified plasma”

172

Peter Weber (ICFO - The Institute of Photonic Sciences, Spain) “Coupling Graphene Mechanical Resonators to Superconducting Microwave cavities”

173

Achim Woessner (ICFO - The Institute of Photonic Sciences, Spain) “Highly confined low-loss plasmons in graphene-boron nitride heterostructures”

176

Qian Wu (Universitat Autònoma de Barcelona (UAB), Spain) “CAFM study of Negative Bias Temperature Instability and Channel hot-carriers degradation in strained and non-strained MOSFETs”

177 Chanyoung Yim (Trinity College Dublin, Ireland) “Investigation of Photodiodes from Vapor Phase Grown MoS2”

179

Oral - PhD (parallel session)

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www.nanobiomedconf.com

Tentative programme

deadlinesconferencefees


1Earth-Life Science Institute, Tokyo Institute of Technology, -12-1 Ookayama,

Meguro-ku, Tokyo 152-8550, Japan. 2PRESTO, Japan Science and Technology Agency

Abstract: Biologically inspired computing architectures are expected to overcome the limitations of conventional technologies in terms of solving computationally demanding problems, reducing energy consumption, and so on. We demonstrated that a single-celled amoeboid organism (a plasmodial slime mold P. polycephalum), which exhibits complex spatiotemporal oscillatory dynamics and efficient decision-making capabilities, can be used to search for a solution to a very hard combinatorial optimization problem (Fig.1) [1]. Aono modeled the spatiotemporal dynamics by which the amoeba searches for the solution and showed that the model, called “AmoebaSAT,” can be implemented by various nanophotonic and nanoelectronic systems that exhibit suitable stimulus response and spatiotemporal dynamics resembling the behavior of the amoeba [2,3]. In fact, photoexcitation transfer phenomena in quantum dots (QDs) generate the amoebalike spatiotemporal dynamics and can be used to solve the Satisfiability problem (SAT), which is the problem of judging whether a given logical proposition is self-consistent (Fig. 2) [4]. SAT is an NP-complete problem that is believed to become intractable for conventional digital computers when the problem size increases, and fast SAT solvers are useful for diverse. AmoebaSAT is several orders of magnitude faster than the fastest-known stochastic local search algorithm for randomly generated 3-SAT instances. These results indicate the potential for developing highly versatile nanoarchitectonic computers that

realize powerful computing with low energy consumption.

References

[1] L. Zhu et al., BioSystems, 2013. [2] M. Naruse et al., Phys. Rev. B, 2012. [3] S. Kasai et al., Appl. Phys. Lett., 2013. [4] M. Aono et al., Langmuir, 2013.

Figure 1. Amoeba-based computer for solving the 8-city

traveling salesman problem.

Masashi Aono1,2

[email protected]


Figure 2. Amoeba-inspired nanophotonic computer for solving the 4-variable satisfiability problem

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ICFO – The Institute of Photonic Sciences, Castelldefels (Barcelona), Spain

Carbon nanotubes and graphene offer unique scientific and technological opportunities as nanoelectromechanical systems (NEMS). Namely, they have allowed the fabrication of mechanical resonators that can be operable at ultra-high frequencies and that can feature high quality factors. In addition, nanotubes and graphene have exceptional electron transport properties, including ballistic conduction over long distances. Coupling the mechanical motion to electron transport in these remarkable materials is thus highly appealing. Here, I will review some of our recent results on nanotube and graphene resonators, including mass sensing at the proton mass level [1], force sensing with ~10 zN/Hz1/2 noise [2], and the measurement of quality factors up to 5 million [3].

References

[1] J. Chaste, A. Eichler, J. Moser, G. Ceballos, R. Rurali, A. Bachtold, Nature Nanotechnology 7, 301 (2012).

[2] J. Moser, J. Güttinger, A. Eichler, M. J. Esplandiu, D. E. Liu, M. I. Dykman, A. Bachtold, Nature Nanotechnology 8, 493 (2013).

[3] J. Moser, A. Eichler, J. Güttinger, M. I. Dykman, A. Bachtold, Nature Nanotechnology, in press.

Figure 1. Suspended multi-element all-carbon vibrational structure, which consists of two graphene mechanical resonators coupled by a multi-wall nanotube beam.

Adrian Bachtold

[email protected]


WITec GmbH, Ulm 89081, Germany

Introduction Carbon in its various forms is used in a multitude of macroscopic and microscopic devices. Depending on the device, different material properties are of key relevance to ensure the performance of the devices. Especially for the one and two dimensional form of carbon (i.e. nanotubes and Graphene) the combination of various analytical techniques often leads to the most appropriate understanding of the device. The aim of this contribution is to illustrate the various fields of application of combined confocal Raman, AFM, SNOM and/or SEM measurements with a focus on carbon materials. The value of nano-carbons for testing state of the art microscopes will also be highlighted. Materials and methods New microscopic techniques are developed continuously to improve resolution but also to increase the amount of information obtainable from the samples. The confocal Raman microscope, a combination of a confocal microscope with high sensitivity Raman spectroscopy, provides chemical imaging with diffraction-limited resolution [1]. This technique is capable of characterizing macroscopic tools such as sanding disks or drill heads consisting of diamonds or diamond like carbons in terms of purity, crystallinity, and stress states [2,3]. The same microscopy technique can also be employed to gain information on the distribution of different forms of carbon as filler in various polymeric materials due to the unique Raman bands of the carbon allotropes [4]. For nano-carbon allotropes a combination of the confocal Raman microscope with AFM and SNOM leads to their more comprehensive characterization.

AFM provides information about the geometric dimensions of the nano-carbons, whereas SNOM enables optical resolution beyond the diffraction limit while maintaining all optical contrast methods. Furthermore, by combining these two methods with Raman spectroscopy, the resolution of molecular imaging can be improved tremendously. Results and discussion The advantage of the combination of Raman and SNOM is demonstrated in Fig. 1. The Raman image presented in Fig. 1a is the integrated intensity of the G band which reveals the presence of a graphene sheet consisting of a monolayer, a double layer and a multilayered graphene (brightest areas). Furthermore, from the intensity distribution of the D band, it is possible to determine the chirality of graphene based on a diffraction limited optical method [5]. Fig. 1b highlights the same sample area, but this time measured in SNOM mode, revealing the transparency of the graphene layers as a function of number of layers (Fig. 1c). Due to the one- or two-dimensional confinement of nanotubes or graphene respectively, these nano-carbons are ideal materials to demonstrate the resolution and sensitivity of such high resolution, high sensitivity microscopic systems. The one-dimensional carbon nanotubes reveal information regarding the lateral resolution of the confocal microscope (Fig. 2a) whereas the two-dimensional graphene sheets spread on structured silicon substrates reveal the depth resolution and sensitivity of confocal Raman microscopes (Fig. 1b). Additionally RISE Microscopy is a novel correlative microscopy technique that combines confocal Raman Imaging and Scanning Electron (RISE) Microscopy within one integrated microscope

Elena Bailo, Thomas Dieing and Ute Schmidt

[email protected]


system. A new dimension in imaging: ultra-structural SEM complemented with chemical compound information and molecular Raman imaging (fig. 3). Conclusions The large amount of information contained in a Raman image provides information about the molecular and structural composition of carbon macro and nano materials. Combined with high resolution techniques such as AFM, SNOM and/or SEM, these spectral information lead to a more comprehensive understanding of carbon materials can be achieved.

References

[1] T. Dieng, O. Hollricher, and J. Toporski `Confocal Raman Microscopy´ Springer Series in Optical Sciences 158, 2010.

[2] K. Bennet, K. Lee, J. Kruchowski, S-Y Chang, M. Marsh, A. Van Orsow, A. Paez, and F. Manciu, 'Development of Conductive Boron-Doped Diamond Electrode: A Microscopic, Spectroscopic, and Voltammetric Study', Materials, 6 (2013), 5726-41.

[3] O. Hollricher and H. Fischer, `Confocal Raman Imaging of Diamond Film` The Application Notebook – March 2008.

[4] U. Schmidt, J. Mueller, and J. Koenen `Confocal Raman Imaging of Polymeric Materials´ Springer Series in Optical Sciences 158, 2010.

[5] Y. M. You, ZhenHua Ni, Ting Yu, and ZeXiang Shen, 'Edge Chirality Determination of Graphene by Raman Spectroscopy', Applied Physics Letters, 93 (2008), 163112..

Figure 1. Raman SNOM study of graphene: intensity of Raman G band (a), SNOM image (b), and decrease of transparency of graphene as a function of number of layers.

Figure 2. Carbon nano-materials are ideal objects to demonstrate the resolution and sensitivity of high resolution, high sensitivity microscopic systems: lateral resolution of a confocal Raman microscope measured on carbon nano-tubes (a) and depth resolution measured on grapheme sheets spread on microstructures Si substrate (b).

Figure 3. (a) SEM image of a graphene sample. (b) Color-coded confocal Raman image. The colors display the graphene layers and wrinkles. Image parameters: 20 μm x 20 μm, 150 x 150 pixels = 22,500 spectra, integration time: 0.05 s/spectrum. (c) SEM image overlaid with the confocal Raman image.

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1Institut de Ciència de Materials de Barcelona, ICMAB-CSIC. Campus UAB, 08193-Bellaterra. Spain 2Institut Català de Nanociència i Nanotecnologia, ICN2, Campus UAB, 08193 Bellaterra. Spain

High quality La2/3Sr2/3MnO3 thin films prepared by sputtering are studied by Conducting Scanning Force and Magnetic Force Microscopy. Film surface consists of one unit cell steps separating atomically flat terraces, with a surface roughness on the terraces lower than 0.3Å. In spite of the extremely flat surface morphology observed, simultaneously acquired topography and current maps revealed a considerably intensity along lines superimposed on a uniform current background. These enhanced conducting lines were not randomly distributed but forming domains with periodic arrays with perpendicular orientations. Line periodicity within each domain coincides with the lateral size of each crystallographic twin as observed by XRD and SEM, thus confirm that the observed lines correspond to the precise position of the twin boundaries. I-V characteristics indicate an important enhancement of the electronic response at the twin boundaries locations. Values of the measured current for a given voltage may differ by one order of magnitude. A clear magnetic signature is also detected at the twin boundaries locations. The origin of this large difference is still under consideration, but it seems that an increase in the density of states at the boundaries might have an important contribution.

Ll. Balcells1, M. Paradinas1, R. Galceran1, Z. Konstantinovic1, A. Pomar1, R. Moreno2, J. Santiso2, N. Domingo2, F. Sandiumenge1, C. Ocal1 and B. Martinez1


1ICN2 - Institut Català de Nanociència i Nanotecnologia, Campus UAB, 08193 Bellaterra

(Barcelona), Spain 2Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Wien, Austria

3Department of Physics, University of Helsinki, P.O. Box 43, 00014 University of Helsinki,

Finland 4ICREA - Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain

The design of graphene-based gas sensors involves three fundamental components: the sensitive graphene-based material, the device design and the selectivity performance. In the sensitive material context, graphene synthesized by mechanical exfoliation has been proven as a suitable sensor material after achieving gas detection at concentrations of one part per billion [1]; however, mechanical exfoliation is not scalable to mass-production of devices. In contrast, highly-damaged graphene like reduced graphene oxide can be synthesized at low cost and large scale, but the sensitivity is diminished to less than one part per million [2]. The most promising way to synthesize large-area high-quality graphene is chemical vapor deposition (CVD), which usually results in a polycrystalline material. This material consists of a variety of misoriented graphene grains with grain boundary interfaces. These grain boundaries are made up of non-hexagonal carbon rings with high chemical reactivity, which can increase the sensitivity up to one part per trillion [3]. In addition, ozone-treated polycrystalline graphene demonstrated significant enhancement of sensing performance compared with the untreated material [4]. Nevertheless, despite the promise of polycrystalline graphene, the sensing mechanisms of this material are not fully understood. In this work, we perform numerical simulations of quantum transport in oxygen-doped polycrystalline graphene samples. To carry out the transport calculations we use a real-space order-N quantum wave packet approach to compute the Kubo-Greenwood electrical conductivity, which we then relate to the mobility as a function of carrier concentration in order to match with experimental

measurements [5,6]. It has been shown that adsorbed oxygen in graphene brings about epoxide functionalization, triggering strong intervalley scattering and a metal-insulator transition [7]. Additionally, in polycrystalline graphene the grain boundary sites are highly reactive, making those sites likely for epoxide functionalization. Our calculations suggest that this functionalization has a lower impact on the mobility than functionalization within the pristine graphene grains. Thus, the electrical transport behavior of functionalized polycrystalline graphene depends on the spatial extension and distribution of the grain boundaries. This behavior serves as an important design consideration for the optimization of gas sensors based on CVD-grown graphene.

References

[1] F. Schedin et al., Nat. Mater., 9 (2007) 652-655.

[2] Wenjing Yuan et al., J. Mater. Chem., 1 (2013) 10078-10091.

[3] Gugang Chen et al., Appl. Phys. Lett., 101 (2012) 053119.

[4] Min Gyun Chung et al., Sensors and Actuators B, 166-167 (2012) 172-176.

[5] Dinh van Tuan et al., Nano Lett. 13 (2013), 1730-1735.

[6] Aron W. Cummings et al., Adv. Mater. (2014) [Published online doi: 10.1002 /adma.201401389 ].

[7] Nicolas Leconte et al., ACS Nano, 4 (2010), 4033-4038.

J.E. Barrios-Vargas1, Aron W. Cummings1, Jani Kotakoski2, 3, David Soriano1 and Stephan Roche1,4

[email protected]


Figure 1. Polycrystalline graphene sample with epoxide functionalization. Carbon atoms are schematically colored in gray, the carbon atoms in the grain boundary are colored in blue, and the Oxygen atoms are colored in red.

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1Department of Physics, University of Konstanz, 78457 Konstanz

2Zukunftskolleg, University of Konstanz, 78457 Konstanz

We study the non-equilibrium regime of a mechanical resonator at low temperature realized with a suspended carbon nanotube quantum dot contacted to two ferromagnets. Due to spin-orbit interaction [1,2] and/or an external magnetic gradient [3], the spin on the dot couples directly to the flexural eigenmodes, see Fig. 1. Owing to this interaction, the nanomechanical motion induces spin-flips of the electrons passing through the nanotube. When a finite voltage is applied, a spin-polarized current causes either heating or active cooling of the mechanical modes, depending on the gate voltage. Optimal cooling is achieved at resonance transport realized when the energy splitting between two dot levels of opposite spin equals the resonator frequency. We show that weak interaction coupling strength and moderate polarization can achieve ground state cooling.[4]. In a realistic setup, taking into account the intrinsic damping of the mechanical oscillator also increases the minimum phonon occupation. Remarkably, a phonon occupation of nmin ≃ 0.5 is still achieved for Q ≃ 104, small coupling λ/ω = 0.05 and polarizations p > 0.48. The minimal phonon occupation reduces to nmin= 0.2 at p = 1. An occupation of nmin ≃0.5 is also obtained for Q≃105

and p>0.3 (nmin = 0.05 at p = 1). Motivated by a recent experiment which reported large spin-orbit interaction coupling ∆SO [12], one can also

consider coupling constants of order λ/ω = 0.2 which implies a strong reduction of the polarization required for cooling. As example, we find nmin ≃ 0.5 for Q ≃ 104 and p > 0.3. Therefore we conclude that even for modest polarizations, which appears feasible in promising experiments with carbonnanotube quantum dots, quantum ground state cooling is achievable.

References

[1] M. S. Rudner and E. I. Rashba, PRB 81, 125426 (2010).

[2] A. Pályi, P. R. Struck, M. Rudner, K. Flensberg and G. Burkard, PRL 108, 206811 (2012)

[3] D. Rugar, R. Budakian, H. J. Mamin and B. W. Chui, Nature 430, 329 (2004)

[4] P. Stadler, W. Belzig and G. Rastelli, arXiv: 1404.0485.

Figure 1. Schematic view of a carbon nanotube quantum dot suspended between two ferromagnetic leads. Due to the nanotube spin-orbit interaction and/or to a magnetic field gradient, the dot spin’s component parallel to the mechanical displacement u is coupled to the flexural mode with a dimensionaless coupling constant λ/ω.

Wolfgang Belzig1, Pascal Stadler1 and Gianluca Rastelli1,2

[email protected]


Figure 2. Non-equilibrium occupation n of the mechanical resonator as a function of source drain voltage and energy level of the dot ε0 for fully polarized ferromagnetic leads with anti-parallel magnetization. The dashed line corresponds to the alignment of a spin-resolved energy level with the chemical potential on the left contact. The insets show the processes for cooling (I) and heating (II), respectively. The temperature of the mechanical resonator is set to kBT=10ω.

Figure 3. Minimal Phonon occupation along the vertical axis ε0=0 of Fig. 1 as a function of polarization for different temperatures at resonance. The bosonic thermal occupation is denoted as nB.

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DIPC (Donostia International Physics Center) Paseo Manuel de Lardizabal, 4 20018 Donostia-San Sebastián (Gipuzkoa), Spain

The electronic scattering properties of defected armchair single-walled carbon nanotubes are investigated by analytical and numerical methods [1-3]. Evaluation of the local density of states and its Fourier transform shows that electron scattering depends on the interplay between tube and defect symmetries [3]. Particularly, the conservation of the pseudo-spin and particle-hole symmetry plays a crucial role. It is shown that the lack of the latter is responsible for the pseudo-spin selection rules observed in the experiments by Ouyang et al. [4]. The symmetry breaking arises from the lattice reconstruction appearing, e.g., in 585 di- vacancies and Stone-Wales defects. We report also comparison with other experiments [1,5]. Our results could pave the way for a possible pseudo-spin filter device.

References

[1] G. Buchs, D. Bercioux, et al., Phys. Rev. Lett. 102, 245505 (2009).

[2] D. Bercioux, et al., Phys. Rev. B 83, 165439 (2011). [3] L. Mayrhofer & D. Bercioux, Phys. Rev. B 84,

115126 (2011). [4] M. Ouyang, J.-L. Huang, and C. M. Lieber, Phys. Rev.

Lett. 88, 066804 (2002). [5] J. Lee, et al., Phys. Rev. Lett. 93, 166403 (2004).

Figure 1. Density plot of the Fourier transformed local density of states as a function of the exchanged momentum and energy for the case of two 585 DV defects with tD = 0.5t. In panel (a) we consider two Type I DV defects, in panel (b) two Type I and Type II DV defects. The signal at k ∼ 25.5 nm−1 is associated with Rx, the smallest length scale of the armchair SWNT along the x axis [3].

Dario Bercioux


Institut Néel, CNRS and UJF, 25 rue des Martyrs, 38042 Grenoble, France.

We present recent studies exploring the merits of specific many-body-perturbation theories, the so-called GW and Bethe-Salpeter (BSE) formalisms, in predicting the quasiparticle and optical excitation energies in organic systems. We will focus on three important examples, namely: (a) charge-transfer excitations [1] in donor-acceptor complexes – including “hot” charge-transfer excitations [2] relevant for understanding organic or hybrid photovoltaic cells, (b) recent developments in calculating electron-phonon coupling matrix elements within the GW formalisms, [3] and (c) a comparison between GW/BSE and high-level coupled-cluster (exCC3) calculations in predicting the excitation energies of an important family of fluorescent dyes. [4] In the later case, the importance of nonlocal correlations is emphasized, with much consequences on the future design of range-separated nonlocal exchange-correlation functionals. Our calculations are performed with the FIESTA package, implementing the GW and Bethe-Salpeter formalisms with an accurate contour deformation, resolution-of-the-identity (Coulomb metric) and Gaussian bases formulation. Scalability tests beyond 60,000 cores and for systems comprising several hundred atoms will be presented.

References

[6] Duchemin, T. Deutsch, X. Blase, Phys. Rev. Lett. 109, 167801 (2012).

[7] I. Duchemin and X. Blase, Phys. Rev. B 87, 245412 (2013).

[8] C. Faber, P. Boulanger, C. Attaccalite, I. Duchemin, X. Blase, in preparation.

[9] P. Boulanger, D. Jacquemin, I. Duchemin, X. Blase, J. Chem. Theory Comput. 10, 1212 (2014).

Figure 1. (Top) Scalability of the Fiesta code up to 61440 cores and 128 TFlops (GENCI Curie thin nodes). Performances for one GW iteration performed on a C60 molecule and a C60 dimer at the TZP basis level (courtesy Ivan Duchemin and European PRACE project SolarFiesta). (Bottom) Lowest singlet excitation energies in cyanine chains as a function of the number of carbon atoms. The shaded area represents TDDFT calculation with semilocal, global and range separated hybrids. The red squares are the GW/BSE results. Energies are reported as differences with respect to the coupled-cluster exCC3 reference.

X. Blase


1Dept. of Micro and Nanotechnology, DTU-Nanotech, and Center for Nanostructured

Graphene (CNG) Technical University of Denmark, Build. 345 east, 2800 Kongens Lyngby, Denmark; 2School of Physics, Huazhong University of Science and Technology, Wuhan, China

3Donostia International Physics Center (DIPC) – UPV/EHU, Donostia-San Sebastian, Spain

4Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark

The effects of electronic current on the atomic structure of nano-scale conductors have become accentuated with the continued down-scaling of electronics. In the extreme scaling limit the position of a few atoms may control the operation of a nano-scale device. Thus it is important to be able to investigate the effects of atomic geometry on the transport and of the current on the atomic geometry. Due to the complexity of the problem computer simulations play an important role. We present theory based on non-equilibrium Greens functions (NEGF) in combination with density functional calculations as implemented in the SIESTA, TranSIESTA, and Inelastica packages [1]. We present examples of first principles simulations of the interplay of the electronic current and atomic dynamics and in metallic and molecular contacts, as well as in graphene-based nano-junctions in the presence of electrostatic gating. The energy exchange between electrons and vibrations which can be detected in current spectroscopy, and yield information about the electronic resonance structure in the junction [2]. This provides an opportunity for direct comparison between experiments and theory. On the other hand, we demonstrate how a high current density can lead to other energy-transfer mechanisms than the local Joule heating in the junction. In particular, the current can cause several types of instabilities [3,4,5,6,7].

References

[1] www.icmab.es/siesta http://sourceforge.net/projects/inelastica

[2] Lü, Rasmussen, Foti, Frederiksen, Gunst, Brandbyge, Phys. Rev. B 85, 81405R (2014)

[3] Lü, Brandbyge, Hedegård, Nano Lett. 10, 16571663 (2010)

[4] Lü, Brandbyge, Hedegård, Todorov, Dundas, Phys. Rev. B 85, 245444 (2012)

[5] Lü, Gunst, Hedegård, Brandbyge, Beilstein J. Nanotechnol. 2, 814 (2011)

[6] Lü, Hedegård, Brandbyge, Phys. Rev. Lett. 107, 46801 (2011)

[7] Gunst, Lü, Hedegård, Brandbyge, Phys. Rev. B. Rapid Comm., 88, 161401 (2013).

Mads Brandbyge1, J.-T. Lü2, T. Gunst1, N. P. Andersen1, R. B. Christensen1, P. Hedegård3, G. Foti4, and T. Frederiksen4

[email protected]

http://www.icmab.es/siesta

http://sourceforge.net/projects/inelastica


1 ICN2 - Institut Catala de Nanociencia i Nanotecnologia, Campus UAB,

08193 Bellaterra Spain 2 Departament de Disseny i Programació de Sistemes Electrònics, UPC - Universitat

Politècnica de Catalunya Av. Bases, 61, 08242 Manresa (Barcelona), Spain 3 CSIC, ICN2 Building ,08193 Bellaterra (Barcelona), Spain

Since its advent, Atomic Force Micorscopy (AFM) has enabled probing single nanostructures, mapping heterogeneous compositional variation in surface properties or studying molecular interactions. Initially the AFM was developed to operate in the quasistatic or DC mode but dynamic modes of operation where introduced to reduce lateral forces while imaging and enhance versatility. In terms of nanoscale processes and properties, a main advantage of dynamic AFM modes over DC modes relates to their capacity to simultaneously probe both conservative and dissipative forces while tracking the topography for imaging. Tip-sample force reconstruction maps in DC modes suffer from stability resulting in so-called "jump-to-contact" where information for a range of distances before mechanical contact is lost. This is crucial in ambient conditions measurements, where the formation of a water neck between the tip and the sample induces instability at long-range distances. On the other hand, interpreting data acquired from the dynamic modes of operation requires detailed modeling and care as the tip follows a non-monotonic force trajectory during each oscillation cycle. We have applied a model to reconstruct, from simple amplitude and phase versus distance curves, the interaction forces between the AFM tip and a sample in ambient conditions [1]. We will show our results on tip-sample forces on ionic crystals where water layers adsorbed on the surface can be controlled and imaged [2]. We will relate features of the reconstruction forces to different tip-sample interactions before mechanical contact between the tip and the sample occurs. That would include capillary forces, long-range van

der Waals forces and forces arising from the formation of chemical bonds. Tip-sample force interactions reconstructed from measurements on BaF2 and CaF2 (111) faces reveals the ability of BaF2 to structure water layers even at room conditions [3].

References

[1] C. A. Amadei, S. Santos, S. O. Pehkonen, A. Verdaguer, M. Chiesa. J. Phys. Chem. C. 117 - 40, 20819 – 20815 (2013)

[2] S. Santos, A. Verdaguer, T. Souier, N. H Thomson and M. Chiesa Nanotechnology 22, 465705, (2011)

[3] A. Verdaguer, J.J. Segura, L. Lopez-Mir, G. Sauthier, J.Fraxedas J. Chem. Phys. 138, 12 (2013).

Figure 1. a) Tip-sample interaction reconstruction on water patches adsorbed on BaF2 and CaF2. b) AFM image of a 1 nm height water patch on BaF2.

A. Calò1, S. Santos2 and A Verdaguer1,3


1 Departament d’Enginyeria Electrònica, Universitat Autònoma de Barcelona,

Bellaterra, Spain 2 Departamento de Física de la Materia Condensada, Universidad Autónoma

de Madrid, Cantoblanco, Spain

In order for graphene and other two-dimensional materials to become competitive players amongst the myriads of electronic devices, one of the main technological hurdles that must be overcome is achieving a low contact resistance (Rc) so that high frequency performance is not compromised [1]. For graphene, it is often quoted that an Rc value lower than 100 Ω•μm is desirable, while larger values are thought to be a limiting factor on the graphene field effect transistor performance [2,3]. Recent experiments have achieved this landmark value with a top contact geometry [4]. On the other hand, an edge contact has been shown experimentally to achieve contact resistances with similar or lower values than most top contacts [5], challenging the conventional wisdom that having a large contact area will result in a decreased value of the contact resistance. Attempts at explaining this behavior resort to the perceived need of electrons to scatter from a value with kz≠0 to kz=0 when entering the graphene layer. We will argue that ballistic electron injection into graphene (or any other 2D material) is basically a perimeter-dependent phenomenon, dependent only on the atomistic details of the graphene-metal configuration at the edge of the metal. 2D materials have a low current carrying capacity per unit width —related to the number of available orbitals in a given energy window—, which is easily saturated by one or a few orbitals with a good overlap in the metal edge – graphene region. This is clearly illustrated in an imaginary graphene-graphene contact, where there is no backscattering and hence a null Rc is obtained (of course, these junctions are not advisable for realistic devices due

to the higher value of the resistance in graphene with respect to a bulk metal). Our arguments are supported by first principles calculations of a model Al/Graphene flake contact, showing a square root dependence of the transmitted current with the contact area (Fig. 1), and graphene with a varying overlap on top of a Ni(111) surface [6], where it is shown that a large fraction of the theoretical maximum of the conductance per unit width is achieved even with a very small overlapping region between the graphene and the Ni(111) surface (Figs. 2 and 3). We will also show that these conclusions are similar for physisorbed graphene. From these results it can be concluded that the experimentally observed high contact resistances in metal – 2D material junctions may be amendable if proper care is taken that the edge region has an intimate contact with the metal. In fact, having a large overlapping region between the metal and the 2D material may be detrimental to the goal of a low contact resistance. We acknowledge financial support by the Spanish Ministerio de Economía y Competitividad under Projects Nos. TEC2012-31330 and FIS2010-21883 and by Generalitat Valenciana under Grant PROMETEO/2012/011. We also acknowledge computational support from the CCC of the Universidad Autónoma de Madrid. Also, the research leading to these results has received funding from the European Union Seventh Framework Programme under grant agreement No. 604391 Graphene Flagship.

Xavier Cartoixà1, K L N Acharya2, Juan José Palacios2

[email protected]


References

[1] J. S. Moon and D. K. Gaskill, IEEE Trans. Microwave Theory Tech. 59, (2011) 2702.

[2] A. Venugopal, L. Colombo and E. M. Vogel, Appl. Phys. Lett. 96, (2010) 013512.

[3] Bo-Chao Huang, Ming Zhang, Yanjie Wang and Jason Woo, Appl. Phys. Lett. 99, (2011) 032107.

[4] J. S. Moon, M. Antcliffe, H. C. Seo, D. Curtis, S. Lin et al., Appl. Phys. Lett. 100, (2012) 203512.

[5] L. Wang, I. Meric, P. Y. Huang, Q. Gao, Y. Gao et al., Science 342, (2013) 614.

[6] Y. Gamo, A. Nagashima, M. Wakabayashi, M. Terai and C. Oshima, Surf. Sci. 374 (1997) 61.

Figure 1. Left: Metal-graphene flake contact. Right: Current vs number of atoms in the contact (points), and a fit of a square root dependence (line).

Figure 2. Relaxed Graphene / Ni(111) structure with the amount of overlapping zigzag chains indicated

Figure 3. Minority spin line conductivity corresponding to the structure in Fig. 2.

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1Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, E-08193, Bellaterra, Barcelona, Spain .

2Institut d’Investigacions Biomèdiques de Barcelona (IIBB-CSIC); Institut d’Investigacions Biomèdiques August Pi i Sunyer

(IDIBAPS). c/Rosselló 161, 08036 Barcelona, Spain. CIBER Epidemiología y Salud Pública (CIBERESP), Spain

Given the intercalation properties of graphite, electrochemical oxidation may be used to exfóliate graphene layers, that may get stabilized either by surfactant counterions, or by the same species that will generate the hybrid finally. Further reduction could return the graphene state to the original oxidation state, with additional ion intercalation of opposite sign. The same procedure is useful when trying to develop nanostructured materials to be used as electrodes in biological systems, such as the ones used in Parkinson treatment. Nanostructuring carbon nanotubes or graphene within electroactive materials may prevent the inflammation derived form phagocitosis, and the toxic effects observed often with nanoparticles. The present work shows new materials and methods based on graphene, carbon nanotubes and iridium phases, and the electrochemical properties and cycling, as well as the optimal biocompatibility found in neural cells media.

References

[1] M. Alanyologlu, J. Oró, N. Casañ-Pastor. Carbon, 50, 2012 , 142; A. M. Cruz, Ll. Abad, N. M. Carretero, J. Moral-Vico, J. Fraxedas, P. Lozano, G. Subías, N. Casañ-Pastor* J. Phys. Chem. C , 116 , 2012, 5155–5168.

[2] N Carretero, Mathieu P. Lichtenstein, E Pérez, Laura Cabana, Cristina Suñol, N Casañ-Pastor* Acta Biomaterialia, 2014. DOI: 10.1016/j.actbio.2014.06.019.

Nanostructuring is clearly observed with nanotubes. IrOx forms around them in layers, while the nanotube supports the oxide structure as a scaffold. The final material es among the most supporting of neural cell growth.

N. Casañ-Pastor1, N. Carretero

1 E. Perez

1 M.

Alanyologlu1 M. Lichtenstein

2 and

C. Suñol2

[email protected]


Dept.Enginyeria Electronica. Universitat Autonoma de Barcelona (UAB), 08193 Bellaterra, Spain

Introduction Nowadays, with the incorporation of new materials, as graphene or high-k dielectrics, in CMOS devices, their morphological and electrical characteristics must be deeply studied, since they could affect the device performance. As an example, the surface morphology of these materials could be a relevant variability source in ultrascaled devices [1, 2]. Conductive Atomic Force Microscopy (CAFM) has been shown to be a very powerful technique to study the topographic and electrical properties at the nanoscale [3, 4]. However, the CAFM characterization is affected by environment and/or experimental factors as the tip conductivity, radius, etc. In order to evaluate how each of the experimental parameters affects separately, new software has been developed. This tool allows to parameterize the CAFM experimental data measured on a given surface, generate topographical maps with the same physical characteristics, and evaluate the impact of such experimental factors. In this paper, three different structures have been simulated and compared with experimental data. Besides, the role of the tip geometry in each structure has been evaluated. Methodology To evaluate the usefulness of this new tool, three completely different structures have been measured with AFM and simulated with the software: polycrystalline HfO2, graphene epitaxially grown on SiC, and amorphous HfO2. For each structure, firstly, topographical AFM maps were measured and statistical characteristics such as roughness, grain size or grain boundary depth have obtained for a given temperature, tip radius or environment. Afterwards, through Monte Carlo (MC) simulation, the surface is generated using the acceptance-rejection method and the parameters

(considered as inputs) obtained experimentally from the measured maps. Finally, the simulation inputs are optimized by least square method to obtain the best fit in the cumulative probability curves. For the simulations, the CAFM tip has been considered to be a semisphere [5], therefore the convolution algorithm is based on geometric considerations of the mutual excluded volume between tip and sample. This tool can also simulate the current through gate dielectrics. From the band diagram, the quantum mechanical electron transmittance is calculated applying the Airy wavefunction approach [6]. This method is valid for any arbitrary band diagram. Finally, the current at each point of the generated map is calculated using the method in [7]. Results Figure 1 shows three different experimental maps of (a) polycrystalline HfO2, (b) graphene on SiC and (c) amorphous HfO2 and their corresponding simulated images (e,d,f), respectively. The experimental images have been obtained with a nominal tip radius of 20 nm. We can observe that the simulated topography can reproduce the different analyzed samples. To quantitatively prove the good match between the experimental and simulated images, figure 2 shows the cumulative distributions of the heights for several simulations for each sample and the experimental image. Figure 3 shows the roughness value of the simulated images for different tip radius. Note that the rms dependence with the tip radius is greater when the surface geometry has structures of the same order of the tip size (polycrystalline structures). In the polycrystalline sample (with an average grain boundary width of 3.5 nm) the variation of the rms is 65% when the radius changes from 0 to 40 nm. However, in samples with

C. Couso, M. Porti, J. Martin-Martinez, V. Iglesias, M. Nafria and X. Aymerich


flatter surfaces this dependence is weaker: in the amorphous sample the variation is 9%. In order to calculate the tunneling current through the gate dielectric Poisson equation is solved in order to obtain the potential barrier. Figure 4 shows a schematic band diagram for a stack with two materials, where additionally the environment has been taken into account. Figure 5 shows a current map obtained for a polycrystalline HfO2-Si structure. These simulations show that the current flows preferentially through the GB, as has been experimentally observed [4]. Conclusions In this work, a simulation methodology, which allows to reproduce topography CAFM images of samples, has been presented. The generated maps have been compared with experimental results obtaining good agreement between them. Besides, current through a dielectric stack has been calculated from the band diagram at each point of the surface. The current calculation considers the morphology and the electrical properties of the analyzed stack, the environment and CAFM tip properties. This simulation method can be very useful for the evaluation of the unavoidable experimental effects intrinsic to the CAFM technique. Also, the tool can be used to generate high amount of data, reducing the number of long time consuming CAFM measurements.

References

[1] A. Asenov, et. al. IEDM, (2008) 421-425, [2] A. Bayerl, et. al. TDMR, 11(3), (2011) 495-501 [3] M. Nafría, et. al. IEDM, (2011) pp 6.3.1 - 6.3.4, [4] V. Iglesias, et. al. Appl. Phys. Lett. 97, 262906

(2010) [5] P. Markiewicz et. al. JVST 13, (1995) pp 1115 [6] K. F. Brennan, et. al. J. Appl. Phys. 61, 614-

623(1987). [7] FA. Noor, et al. J. Appl. Phys. 108, 093711

(2010.

Figure 1. Experimental topography images a) HfO2 polycrystalline (1x0.5 µm ), b) graphene on SiC (4x2 µm) and c) HfO2 amorphous (1x0.5 µm ) and corresponding simulated images (e,f,g).

Figure 2. Height cumulative probability of experimental and several simulated maps for each sample. a) HfO2 polycrystalline, b) graphene on SiC, c) HfO2 amorphous.

Figure 3. Roughness as a function of the tip radius. The empty symbols represent simulation points and the filled symbols are experimental measurements.

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Figure 4 Schematic band diagram showing any stack with two different materials and having into account the environment barrier.

Figure 5 Simulated current image corresponding to the topography map in fig.1d. The applied bias is 2 V.

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1Universite Paris Diderot, Sorbonne Paris Cite, MPQ, UMR 7162 CNRS, 75205 Paris Cedex

13, France 2Universite Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR 7086 CNRS, 75205 Paris

Cedex 13, France

Quantum interference results from the wave properties of electrons and is a well-known quantum effect in mesoscopic physics [1]. The ability to control quantum interference at the molecular level could improve knowledge of electron transport through molecular systems and provide novel electronic behavior of molecular junctions. Furthermore, the nanometric size of a molecular system implies large energy scales, making it possible to address quantum effects at room temperature. Consequently, quantum interference in molecules has recently attracted great interest, both theoretically [2] and experimentally [3,4]. Generally, such effect is predicted to occur with cross-conjugated molecules, systems are composed of three unsaturated groups, two of which are conjugated to the third but not conjugated to each other. The anthraquinone (AQ) molecule (whose structure is shown in the inset of Figure 1) is of particular interest, because it is intrinsically cross-conjugated as long as contact between the bottom and top electrodes involves the two peripheral aromatic rings. The expected signature of quantum interference in transport through a molecule is a reduction of the transmission resulting from destructive interference, with a clear antiresonance at the energy where interference occurs. I will present our work on the investigation of quantum interference on AQ molecular layers embedded in large-area, CMOS compatible solid-state devices [5]. We have found direct experimental evidence of a large quantum interference effect through measurement of the differential conductance. We have demonstrated that quantum interferences are present at room

temperature and are enhanced as temperature is lowered for molecular layers thicker than a monolayer (Figure1). Furthermore, the experimental signature of the electron-phonon coupling appears at low temperature as the major source of decoherence, extinguishing interference effects. The visibility and robustness of this quantum effect on large area junction confirms the dominant intramolecular charge transport mechanism occurring in the molecular layer, and it paves the way for the development of practical devices based on the control of the coherent electron transport through conjugated systems. Moreover a giant thermoelectric effect has been predicted for single molecule junctions in the vicinity of a node of the transmission function [6]. This is extremely interesting since the electrical energy is here directly converted in thermal energy. In particular the thermopower is predicted to reach a universal temperature independent maximum value of ∼±156μV/K, This enhancement arises because the flow of entropy, which is an incoherent quantity, is not blocked by destructive quantum interference, unlike the flow of electrical current, which can be completely coherent. I will discuss the possibility to realize Seebeck coefficient measurements on AQ based planar junctions.

References

[1] Y.V. Nazarov, Y. Blanter, Quantum Transport: Introduction to Nanoscience, Cambridge University Press: Cambridge (2009).

[2] G.C. Solomon, D.Q. Andrews, M.A. Ratner, Charge and Exciton Transport through

M.L. Della Rocca1, C. Bessis1, C. Barraud1, P. Martin2, J.-C. Lacroix2 and P. Lafarge1

[email protected]


Molecular Wires, Eds L.D.A. Siebbeles, F.C. Grozema, Wiley-VCH: Weinheim (2011).

[3] D. Fracasso, H. Valkenier, J.C. Hummelen, G.C. Solomon, and R.C. Chiechi, J. Am. Chem. Soc. 133, (2011) 9556.

[4] C.M. Guedon, H. Valkenier, T. Markussen, K.S. Thygesen, J.C. Hummelen, and S.J. van der Molen, Nat. Nanotechnol. 7, (2012) 305.

[5] V. Rabache, J. Chaste, P. Petit, M.L. Della Rocca, P. Martin, J.-C. Lacroix, R.L. McCreery, and Philippe Lafarge J. Am. Chem. Soc. 135, (2013) 10218.

[6] J.P. Bergfield, C.A. Stafford, Nano Lett. 9, (2009) 3072.

Figure 1. Measured dI/dV vs V data for an AQ-based junction at 300 K (black circles) and 4 K (blue triangles) with an area of 30×30μm

2. A pronounced antiresonance is present at low voltage.

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1ICN2 - Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193Bellaterra

(Barcelona), Spain 2Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Barcelona), Spain

3Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic

4Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116

Praha 2, Czech Republic 5ICREA - Institucio Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain

6CSIC - Consejo Superior de Investigaciones Cientificas, ICN2 Building ,08193 Bellaterra (Barcelona), Spain

Mechanical stimuli induced by the tip of an atomic force microscopy (AFM) is the basis for the generation of different types of phenomenologies, from flexoelectric fields that can lead to mechanical writing in ferroelectric materials [1] to piezochemical effects due to the dynamics in ionic systems [2]. In this presentation, I will introduce a new electromechanical effect that can be studied by AFM: the piezoresistance coefficients and gauge factors of sensor materials. In this work [3], we have induced an insulator-to-metal transition by applying uniaxial pressure to the material through an Atomic Force Microscope (AFM) tip, measuring a record gauge factors for an oxide material at the nanoscale. We achieve the reversible mechanical control of dielectric gap in a semiconductor oxide that lead to metal-insulator transitions induced by uniaxial stress, demonstrating that local electronic structures can be locally changed by applying uniaxial pressure through an AFM tip. The AFM tip also acts as a sensor and transport measurements through the AFM tip are done through different approaches. In all cases the experimental setup consist of the sample and tip placed in series resulting in a capacitor where the tip is the top electrode and an LSMO thin film substrate between SIO and STO is the bottom electrode. While the features of the I(V) for the lowest applied forces resemble those of a semiconductor, linear Ohmic behavior is achieved for increasing forces with increasing slopes. From the obtained results, we observed an outstanding and reversible decrease of

the resistance of the Sr2IrO4 thin film as a function of increasing mechanical loading force on the AFM tip. We attribute this behaviour to an insulator-to-metal transition caused by pressure induced changes in the Ir-O-Ir bond angle in the plane which produce a closure of the band gap.

References

[1] H. Lu, et al., Science 336, 59 (2012). [2] Y. Kim, et al.,Nanoletters 13 (2013) 4068. [3] N. Domingo, et al, submitted for publication.

Figure 1. Resistance as a function of the applied forcé through an AFM onto Sr2IrO4.

N. Domingo1,6, L. López-Mir1,2,* X. Martí1,3,4, M. Paradinas2, C. Ocal2 and G. Catalán1,5

[email protected]


CEMES CNRS UPR 8011, 29 Rue Jeanne Marvig, BP 94347, F-31055 Toulouse, France

Graphene can be considered as the ultimately thin and high mobility platform that offers a unique opportunity to adiabatically bridge the mesoscopic and molecular electronic properties within a single, one-atom thick 2D material. The corollary experimental challenge is to bring together all production, patterning and contacting techniques that will make it possible to tailor graphene from

typically 1 m down to 1 nm and eventually to individual carbon atoms. In this context, we propose to combine low energy electron beam and chemical etching to design arbitrary graphene patterns over multiple length scale down to sub-10 nm feature size. Our approach is compatible with ultra-high vacuum (UHV) environment and applicable to connected device fabrication. Structural characterization of cut edges and graphene nanoribbons shows crystalline and atomically smooth edges. Next, we have adapted our approach to device configuration. The etching procedure has been successfully adapted to partially suspended graphene leading to connected and gated graphene nanoribbons devices with width below 50 nm. Preliminary transport measurements performed on suspended graphene nanoribbons with crystalline edges will be discussed. The second part will be dedicated to the fine tuning of the electronic properties of graphene. Indeed prospective molecular-scale graphene devices will have to be actuated. Electrostatically gated transport is only one in several options. In particular, we will discuss the prospects of reversibly tuning the charge carrier density of graphene by optical or chemical means.

Erik Dujardin

[email protected]


Public University of Navarre, Arrosadia Campus E-31006, Pamplona, Spain

Sensors based on the luminescent complex platinum tetrakis pentrafluorophenyporphine (PtTFPP) have been prepared by depositing this material onto a plastic-clad silica (PCS) optical fiber. The construction is performed in terms of Layer-by-Layer (LbL) method: the features of the sensors are studied in terms of the concentration of the sensing material and the thickness of the sensing film. The sensors are illuminated with a LED centered at 400 nm, so that the emission of the sensing compound (at 648 nm) is recorded by a spectrometer. A tradeoff is required between the concentration and thickness of the sensing layer, looking for both the sensitivity and kinetics of the response are optimal. The best results obtained offer a signal change around 8 times when the O2 concentration varies from 0% up to 21 %, with a response time of 24 seconds and a recovery time of 6 seconds. Motivation and results The detection and quantification of oxygen sensing is relevant in several fields such as food industry or biomedicine. On the other hand, the features that optical fiber sensors show for gas sensing applications have focused the attention of many researches to this topic. In this background, Layer-by-Layer technique (LbL) offers good results to deposit reagents: the parameters of the construction process can be set to meet the requirements of the final application. Metalloporphyrins are materials used to detect oxygen: they have a high chemical and thermal robustness [2]. This product is not soluble in water, which is a requirement in the LbL method. This inconvenience is overcome by preparing an emulsion of the sensing material with a surfactant that preserves its optical properties [3] (see Figure 1.A). In this manner, it can be deposited with LbL.

This work studies both the sensitivity and kinetics of sensors with different two different concentration of the sensing material: 0.04 mg/mL (concentration A) and 0.8 mg/mL (concentration B). The sensors are prepared with a cleaved ended PCS fiber, onto which the material is deposited [4]. The LbL is an iterative procedure: a construction cycle is known as bilayer, so that the thickness of the sensing film (in the nanometer scale) is expressed in terms of the number of bilayers deposited. Figure 1.B illustrates the emission peak (21% O2) registered for the two concentrations and the different number of bilayers: in the case of concentration A, the signal increases with the thickness, which is not the observed case with concentration B. For the first concentration, the sensing material density is lower, so with more layers, more luminescence is couple into the fiber. However, for concentration B the peak decreases along the process: it is because the film gets too thick and optical losses increases significantly. The higher signal level is recorded with 2 and 4 bilayers for concentration B. In order to check the performance of the sensors, they were exposed to cycles of O2concentrations between 0% and 21%. The emission peak was registered to evaluate the sensitivity and kinetics of the distinct devices. Results are exposed in Figure 2. It is important to highlight that in every case the response is repetitive and the base line level is recovered. Results are summarized in Table 1 and in Table 2. In the case of concentration A, the sensitivity increases with the number of bilayers; response and recovery times are not affected by the number of bilayers, so the thickness is so low that does not affect it. In the case of concentration B, the highest sensitivity is observed with 4 bilayers. The kinetics get worse with more deposited bilayers: the

C. Elosua1, N. de Acha1, I.R. Matias1, F.J. Arregui1

[email protected]


sensing film is too thick and the oxygen needs more time to get adsorpted de adsorpted. Anyway, the best device in terms of sensitivity and response / recovery times is the one obtained with concentration B and 4 bilayers. This work highlights the great potentiality of LbL method to prepare oxygen sensors even with immiscible products, and show how the construction parameters define the response of the final device.

References

[1] G. Decher, Science 277 (1997) 1232–1237. [2] C.S. Chu, Journal of Luminescence, 135 (2013)

5-9. [3] N. Ma, H. Zhang, B. Song, Z. Wang,

X. Zhang, Chem. Mater, 17 (2005) 5065-5069.

[4] P.A.S. Jorge, P. Caldas, C.C. Rosa, et al, Sensors and Actuators B, 103 (2004) 290-299.

Figure 1. (A) Emission of the metalloporphyrin emulsion when illuminated with an UV lamp; (B) Characteristic spectrum of the material deposited onto the fiber and interrogated with a LED at 400nm.

Figure 2. Dynamic responses of the sensors depending on the number of bilayers deposited with concentration (A) and (B). Cycles are set between 0% O2 (baseline) and 21% O2.

Concentration A (0.04 mg/ml Pt-TFPP)

#Bilayers Imax (counts) Dynamic Range Tresponse (s) Trecovery (s) 2 54.68 2.18 30 9 4 51.01 2.57 27 9 6 103.16 2.98 27 6 8 73.76 3.56 24 12

10 117.91 5.11 24 6 Table 1. Response parameters of the sensors prepared with Concentration A depending on the number of bilayers deposited onto the fiber.

Concentration B (0.8 mg/ml Pt-TFPP)

#Bilayers Imax (counts) Dynamic Range Tresponse (s) Trecovery (s) 2 532.22 4 18 9 4 258.31 7.55 24 6 6 61.29 1.91 39 18 8 71.53 1.86 27 27

10 73.29 2.65 39 33 Table 2. Response parameters of the sensors prepared with Concentration A depending on the number of bilayers deposited onto the fiber.

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Instituto de Química Avanzada de Cataluña (IQAC), Consejo Superior de Investigaciones Científicas (CSIC), and CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Jordi Girona 18-26, 08034 Barcelona, SPAIN.

Porous inorganic oxides are usually prepared by sol-gel synthesis in the presence of surfactant systems, which act as templates for the control of the pore size and morphology. In a previous work, we obtained materials with dual meso/macroporous structures, by hydrolizing tetraethyl orthosilicate (TEOS) in the external phase of O/W highly concentrated emulsions, where this external phase was a liquid crystal [1]. However, ethanol released by TEOS hydrolysis produced emulsion instability and also obstructed the formation of ordered mesopores. In the present work, silica with bimodal pore size distribution was obtained by a new simple method [2]. A novel hydrophilic precursor, tetra(2-hydroxyethyl) orthosilicate (abbreviated as THEOS) was hydrolized in the continuous phase of highly concentrated emulsions with a cubic liquid crystal in this external phase stabilized with a polyoxyethylene alkyl ether surfactant. Highly concentrated emulsions possess volumes of dispersed phase higher than 74%, maximum packing for monodispersed spherical droplets [3,4]. Therefore, these emulsions consist of densely-packed droplets, separated by a thin film of external phase [3-5]. In our studies, a cubic liquid crystal was present in these thin films that surround the oil droplets. The hydrolysis and condensation reactions of the precursor were carried out in the cubic liquid crystal, at slightly basic pH. Interestingly, the structure of the cubic liquid crystalline phase, was stable during the sol−gel silica synthesis. As a result, mesoporosity was formed, replicating the same morphology of the

cubic liquid crystal. Moreover the presence of emulsion oil droplets allowed to obtain a interconnected macroporous texture, with morphology similar to that of foams. Consequently, materials that simultaneously possessed mesopores and macropores, were obtained. The mesopores were small (around 4 nm in size), highly monodisperse, well-ordered and with cubic symmetry. In the other hand, the macropores were much larger (with pore sizes between 1 and 5 μm) polidisperse and highly interconnected, replicating the morphology of the highly concentrated emulsion droplets. Monoliths with a specific surface area around 500 m2 g−1 and bulk density of 0.16 g cm−3 were been obtained.

References

[1] J. Esquena; J. Nestor; A. Vílchez; K. Aramaki; C. Solans, Langmuir, 2012, 12334.

[2] J. Nestor, A. Vílchez, C. Solans, J. Esquena, Langmuir, 2013, 432.

[3] K. L. Lissant, J. Colloid Interface Sci., 1966, 22, 462-468.

[4] C. Solans, R. Pons, H. Kunieda, In: Modern Aspects of Emulsion Science; B. P. Binks, Ed.; The Royal Society of Chemistry: Cambridge, UK, 1998; pp 367-394.

[5] J. Esquena, C. Solans, In: Emulsions and Emulsion Stability; J. Sjöblom, Ed.; Taylor and Francis, New York, 2006.

J. Esquena J. Nestor, A. Vílchez and C. Solans

[email protected]


Donostia International Physics Center DIPC and Materials Physics Center CSIC-UPV/EHU, Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián, Spain

Plasmonic particles separated by subnanometric distances (Figure 1a) allows to investigate ultra-fast and ultra-confined optoelectronic effects that emerge due to the influence of the electrons tunneling through the gap on the optical response [1]. The tunneling can completely modify the modal structure of the resonant system (Figure 1b) and it strongly quenches the near fields (Figure1c). We discuss both the fundamental physical phenomena behind this behavior as also its relevance to possible applications such as spectroscopy and light generation by non-linear processes[2]. Of special interest is the identification of these processes in experiments, which have only reached the required level of control in the last years [3]. We are able to satisfactorily analyze different experimental measurements [4] using a Quantum Corrected Model (QCM [5], Figure 1a), which we developed to treat large systems. The QCM also allows revealing the influence of the gap morphology on the experimental signature of the charge transfer and exploring the relative weight on the response of non-local and quantum effects.

References

[1] J. Zuloaga, E. Prodan and P. Nordlander, Nano Letters 9 (2009) 887–891.

[2] D. C. Marinica, A. K. Kazansky, P. Nordlander, J. Aizpurua and A. G. Borisov, Nano Letters,12 (2012) 1333–1339.

[3] J. A. Scholl, A. García-Etxarri, A. L. Koh and J. A. Dionne, Nano Letters 13 (2013) 564–569.

[4] K. J. Savage, M. M. Hawkeye, R. Esteban , A. G. Borisov, J. Aizpurua and J. J. Baumberg, Nature 491 (2012) 574–577.

[5] R. Esteban, A. G. Borisov, P. Nordlander and J. Aizpurua, Nat Commun 3 (2012) 825.

Figure 1. Quantum effects for a plasmonic dimer. a) An effective medium is inserted in the ultra-narrow gap to implement the QCM. (b-c) Extinction and (c) Near Field enhancement at the gap for a dimer of 25nm radius silver spheres as a function of separation distance and energy. The onset of the quantum regime near 0.35nm distance is characterized by a gradual change of the nature of the modes in (b) and the quenching of the near fields in (c).

Ruben Esteban and J. Aizpurua

[email protected]


1 Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK 2 Department of Physics, University of Bath, BA2 7AY, UK 3 Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland 4 Advanced Materials Laboratory, NIMS, 1-1 Namiki, Tsukuba 305-0044, Japan

Fermi surface topology plays an important role in determining the electronic properties of metals [1]. In bulk metals, the Fermi energy is not easily tunable at the energy scale needed for reaching conditions for the Lifshitz transition - a singular point in the band structure where the connectivity of the Fermi surface changes. Bilayer graphene [2,3] is a unique system where both Fermi energy and the low-energy electron dispersion can be tuned using the interplay between trigonal warping and a band gap opened by a transverse electric field. Here, we show that once can drive the Lifshitz transition to experimentally controllable carrier densities by applying large transverse electric fields through a h-BN-encapsulated bilayer graphene structure, and detect it by measuring the degeneracies of Landau levels [4]. These degeneracies are revealed by filling factor -3 and -6 quantum Hall effect states of holes at low magnetic fields reflecting the existence of three maxima on the top of the valence band dispersion. At high magnetic fields all integer quantum Hall states are observed, indicating that deeper in the valence band the constant energy contours are singly-connected. The observation of ferromagnetic quantum Hall states at odd-integer filling factors in the highquality samples enables one to identify several phase transitions between correlated quantum Hall states at intermediate magnetic fields, in agreement with the calculated evolution of the Landau level spectrum.

References

[1] I. Lifshitz. Sov. Phys. JETP 11, 1130 (1960). [2] K. Novoselov, et al. Nat Phys 2, 177–180 (2006). [3] E. McCann & V. Fal’ko. Phys. Rev. Lett. 96, 086805

(2006).

[4] A. Varlet, et al. arXiv: 1403.3244.

Vladimir I. Fal'ko1, Marcin Mucha-Kruczyński2, Anastasia Varlet3, Dominik Bischoff3, Pauline Simonet3, Kenji Watanabe4, Takashi Taniguchi4, Thomas Ihn3 and Klaus Ensslin3


INL, Av José Mestre Veiga, Braga, Portugal

Several groups in the world are able to fabricate artificial nanomagnets assembling atoms one by one on top of a surface, using scanning tunnelling microscopes. Apparently minor differences in the structure, chemical composition and surface orientation of these systems lead to dramatic changes in their electronic and magnetic properties. For instance, when deposited on the same surface (Cu(100) coated with a monolayer of Cu2N), a linear array of 6 Mn atoms [1] deposited along a N rich row, behaves like a quantum spin liquid with strong quantum spin fluctuations whereas a linear array of 6 atoms of Fe behaves like a classical antiferromagnet [2] with two stable Neel states that can be used to store digital information at low temperatures. In contrast, when deposited on the exactly the same surface, an array of 6 Fe atoms along a Cu rich direction couple ferromagnetically [3]. In this talk I will discuss two topics, in connection with these fascinating systems. First, I will discuss our theoretical understanding of the rules that govern these very different magnetic properties, including the interplay between exchange interaction, Kondo coupling and magnetic anisotropy [4]. Second [3], I will discuss the theoretical background [3] that made it possible to obtain, for the first time, an atomic-scale resolution image of spin wave modes in these systems. Understanding these artificial nanomagnets and being able to probe their spin excitations with atomic resolution should pave the way towards their rational design, resulting in a new class of systems, designer nanomagnets.

References

[1] C. F. Hirjibehedin, C. P. Lutz, A. J. Heinrich, A. J. Science 312, (2006)1021.

[2] S. Loth, S. Baumann, C. P. Lutz, D. M. Eigler, A. J. Heinrich, A. J, Science 335, (2012) 196.

[3] A. Spinelli, B. Bryant, F. Delgado, J. Fernández-Rossier, A. F. Otte, Nature Materials 13, (2014) 782.

[4] J. Oberg, R. Calvo, F. Delgado, D. Jacob, M. Moro, D. Serrate, J. Fernández-Rossier, C. F. Hirjibehedin, Nature Nanotechnology 9, (2014) 64.

Figure 1. Top panel: Art image of magnetic adatoms on Cu2N surface, probed with the STM tip. Bottom panel: From reference [], color maps (left, experiment, right theory) of d

2I/dV

2 curves as a function

of bias voltage (vertical axis) for each atom (horizontal axis) on a chain of N=6 Fe ferromagnetically coupled atoms.

J. Fernández-Rossier

[email protected]


1Applied Physics Dept., Universitat Politècnica de Catalunya, J. Girona 3-5,

08034 Barcelona, Spain 2Dept. of Physics and Graphene Research Institute, Sejong University, Seoul 143-747

In the present work we used CVD grown graphene exposed to deep ultraviolet (DUV) light during different times up to 100 min. [1]. It has been described theoretically that oxygen molecules react with graphene in the presence of UV light to produce oxygen containing groups [2], these oxygen atoms form a stable structure on the sites of pristine graphene and induce p-type doping [3].

We analyzed the samples by Raman spectroscopy and transport measurements. Raman spectroscopy suggest p-doping without a significant increase of defects density.

The p-doping of CVD grown graphene is confirmed by transport measurements [4]. The back gate voltage dependent resistivity for single layer graphene is analyzed as function of DUV light exposure time, the maximum resistivity corresponding to the Dirac point is shifted toward positive gate voltage with increasing the DUV light exposure time. Our work demonstrates by Raman spectroscopy and transport measurements a stable and reversible p-doping in CVD grown graphene film with deep ultraviolet (DUV) light.

Terahertz time-domain spectroscopy (THz-TDS) is a non-destructive testing method based on a coherent detection scheme, implementing a phase-sensitive technique that enables broadband measurements of complex material properties, as refractive index, the absorption coefficient or AC conductivity at THz frequencies, up to 2 THz.

The THz measurements are performed in a THz-TDS spectrometer in transmission setup, based on a commercial THz spectrophotometer TERA K8, from Menlo Systems.

The Broadband THz radiation is generated using a 780 nm wavelength femtosecond laser based on erbium-doped optical fiber and it is detected with a

photoconductive antenna. The output of the laser is split into a pump (generating) and a probe (detecting) beams by a polarizing beam splitter, travelling throw two different optical paths to the emitter and the detector antenna, respectively. One path has a variable length, in order to control the pulses delay arriving to the corresponding antenna.

Due to the interaction with the laser pulses electron-hole pairs are generated in the antenna semiconducting material, then a transient photocurrent is induced by applying a bias voltage to the antenna, the accelerated charge carriers emit a THz electrical field proportional to the time-derivative of the photocurrent. This THz radiation is modulated at a 10 kHz and focused on the sample guided through polymer lenses. The transmitted radiation through the sample is focused on a THz detector antenna which is gated by the probe (detection) laser beam. Finally the recorded time trace is transferred into frequency domain by Fourier transform for spectroscopic analysis. The conductance and refraction index of the sample can be deduced.

We analyzed doped and undoped grapheme samples on three different substrates: glass, PET and silicon.

References

[1] Iqbal MW, Singh AK, Iqbal MZ, Eom J, J Phys-Condens Mat., 24 (2012), 33.

[2] Cheng YC, Kaloni TP, Zhu ZY, Schwingenschlogl U, Appl. Phys. Lett., 7 (2012) 101.

[3] Dai JY, Yuan JM, Phys. Ver. B, 16, (2010) 81. [4] Tongay S, Berke K, Lemaitre M, Nasrollahi Z et

al., Nanotechnology, 22 (42) (2011). [5] N. Rouhi, S. Capdevila, D. Jain, K. Zand, Y.Y.

Wang, E. Bown, Ll. Jofre, P. Burke, Nano Research (2012) 5, Issue 10, 667.

N. Ferrer-Anglada1, D. Gabriel1 , M. Z. Iqbal1,2 and J. Eom2 [email protected]


1Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany

2 Theoretical Physics and Quantum Technologies Department, National University of

Science and Technology MISIS, Moscow 119049, Russia

We report a theoretical study of radiation-induced quantum interference effects in low-dimensional graphene based n-p and n-p-n junctions. It has been shown that the resonant interaction of propagating electrons with an electromagnetic field (EF) can lead to the appearance of the dynamic gap in the quasi-particle spectrum [1-2]. Such a gap bears a remarkable resemblance to the Rabi frequency. The presence of the gap leads to a suppression [1] or enhancement [2] (ballistic photocurrent) of the electron transport in graphene based nanostructures. In the presence of an externally applied radiation the ballistic transport of electrons in n-p junctions is determined by two processes, namely, by the resonant absorption of photons near the "resonant points" and by the strong reflection from the junction interface, occurring at the "reflection points". There are two paths corresponding to the propagations of electrons through the junction (see Fig. 1), and the interference between these two paths manifests itself by large oscillations of the ballistic photocurrent Iph as a function of the gate voltage VG or the frequency Ѡ of the radiation. This coherent quantum phenomenon resembles Ramsey quantum beating and Stueckelberg oscillations well-known in atomic physics [3]. In the ballistic transport of irradiated graphene based n-p-n junctions (see Fig. 2a) we studied the quantum resonances. By making use of the Floquet analysis and the quasi-classical approach we analyze the dynamics of electrons in the presence of time and coordinate dependent potential U(z,t) (Fig. 2b). In the absence of EF the resonant tunneling results in a set of sharp resonances in the

dependence of dc conductance σ on the gate

voltage VG [4]. In irradiated n-p-n junctions we obtain the Fano-type resonances (Fig. 3) that is due to the interplay of two effects: the resonant tunneling through quasi-bound states [4] and the quantum-interference effect in the region between the resonant points, where the resonant absorption (emission) of photons occurs, and junction interfaces. A suitable radiation frequency may be in the THz or in the infrared optical region. The effects can be observed in one- and two-dimensional n-p and n-p-n junctions based on carbon nanotubes, monolayer or bilayer graphene nanoribbons.

References

[1] M. V. Fistul and K. B. Efetov, Phys. Rev. Lett., 98 (2007) 256803.

[2] S. V. Syzranov, M. V. Fistul, and K. B. Efetov, Phys. Rev. B, 78 (2008) 045407.

[3] M. V. Fistul, S. V. Syzranov, A. M. Kadigrobov, and K. B. Efetov, Phys. Rev. B, 82 (2010) 121409(R).

[4] P. G. Silvestrov and K. B. Efetov, Phys. Rev. Lett., 98 (2007) 016802.

M. V. Fistul1,2 and K. B. Efetov1,2 [email protected]


Figure 1. Schematic of irradiated graphene based n-p junction and typical electron trajectories.

Figure 2. a) Schematic of irradiated graphene based n-p-n junction; b) The quasi-classical phase trajectories of electrons in irradiated n-p-n junctions.

Figure 3. The typical resonant peaks in the dependence of dc conductance on the gate voltage, σ(VG). The peaks shape

changes from a symmetric one in the absence of EF (red curve) up to asymmetric one, i.e. the Fano type, as the EF is applied [blue curve].

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1Instituto de Ciencia Molecular (ICMol). Universidad de Valencia.

Catedrático José Beltrán Martínez nº 2, 46980, Paterna, Spain. 2 Institut de Chimie Moléculaire et des Matériaux d’Orsay CNRS, Université Paris Sud 11,

91405 Orsay, France

In the race towards the miniaturization in nanoelectronics, magnetic nanoparticles (MNPs) have emerged as potential candidates for their integration in ultra-high density recording media. Molecular-based materials open the possibility to design new tailor-made MNPs with variable composition and sizes, which are benefited by the intrinsic properties of these materials. Among them, bimetallic, cyanide-bridged nanoparticles of the family of Prussian blue analogues (PBA-NPs) have been broadly studied.[1] Before their implementation in real devices is reached, a precise organization on surfaces and a reliable characterization and manipulation of their individual magnetic behavior are required. We will show how molecular-based MNPs are accurately organized on surfaces by soft-lithography and how their individual magnetic properties are detected and tuned by means of low-temperature magnetic force microscopy[2] (LT-MFM) with variable magnetic field. The magnetization reversal on dispersed and organized MNPs is investigated, and the temperature dependence of their magnetic response is evaluated. Finally we will present the results from magnetic measurements performed with a functionalized-MFM tip by a PBA-NP (Figure 1). The new contrast observed with this PBA-NP-tip is compatible with an in-plane magnetized MFM tip (as opposed to the original out-of-plane MFM tip). Therefore, this functionalization converts the ~50 nm tip into a ~19 nm tip with an effective magnetic moment in the +x direction, enriching the information that can be extracted from the magnetic images.

References

[1] (a) Y. Prado, et al. Chem. Commun. 3 (2011) 1051; (b) D. Brinzei, et al. J. Am. Chem. Soc. 129 (2007) 3778

[2] U. Hartmann Annu. Rev. Mater. Sci., 29 (1999) 53.

Figure 1. 3D magnetic images (520 nm x 520 nm) acquired with the regular MFM tip (left) and the functionalized PBA-NP-tip (right). Three NPs are highlighted and zooms in of 115 nm x 115 nm show the different magnetic contrasts for each case. A schematic of the magnetic contrast for the different situations is shown for clarity.

A. Forment-Aliaga1 E.Coronado1, S. Kumar1, S. Mañas1, E. Pinilla-Cienfuegos1, L. Catala2 and T. Mallah2 [email protected]


1 Departament de Física Fonamental and Institut de Nanociència i Nanotecnologia,

Universitat de Barcelona, 08028 Barcelona, Spain 2 Department of Physics and Center for Advanced Nanoscience, University of California

San Diego, La Jolla CA 92093, USA 3 Department of Chemical-Physics, BCMaterials, University of the Basque Country

UPV/EHU, 48940 Leioa, Spain. 4 IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain.

5 Advanced Light Source, Lawrence Berkeley Nat Laboratory, Berkeley, CA 94720, USA

Confining the dimensions and geometry of magnetic structures down to critical length scales such as the ferromagnetic (FM) exchange length or the domain wall width results in intriguing new phenomena not observed in the corresponding bulk material. In this regard, a proximity effect such as exchange bias (EB), which refers to the unidirectional anisotropy induced in FM films due to the interfacial exchange interaction with an antiferromagnetic (AF) layer upon cooling through the AF Néel temperature (TN), is of particular interest [1]. The EB effect has become key to numerous applications such as spin valves [2] and the stabilization of the magnetization in nanoparticles against thermal excitations [3]. Recently, FM/AF nanostructures exhibiting both negative [1] and positive EB [4-7], i.e., hysteresis loops shifted either against or along the cooling field direction, respectively, have been proposed as model systems for multistate switching memory units [8, 9]. The sign of EB can be influenced either by the cooling field or by changes in the domain configuration in both the bulk of the AF and at the FM/AF interface [5, 10- 12]. Patterning allows the control of writing fields and the design of the multistate cells [9]. In this work, we show that the spatial confinement of the FM correlation length, either through thickness variation of the FM layer or laterally via patterning, drastically affects the AF domain structure in exchange-biased Ni/FeF2 nanostructures. Direct observations of the spin configuration at both sides of the FM/AF interface

performed by photoemission electron microscopy reveal that the final spin structure is determined by the competing balance between the two dissimilar magnetic length scales. A coexistence of EB domains with opposite directions can be tuned in Ni/FeF2 bilayers for Ni thicknesses below 10 nm. Patterning of the nanostructures with antidots using focused-ion-beam lithography destabilizes further the FM order. In particular, it promotes the coexistence of opposite exchange-bias domains below a critical antidot interspace in the order of a few FeF2 crystal domains. Our results suggest that dimensional constrictions in the FM layer might be used to trigger the AF spin structure in spintronic devices or ultra-high density storage media. This work was supported by Spanish MINECO (MAT2012-33037), Catalan DURSI (2009SGR856), European Union FEDER funds (Una manera de hacer Europa), UPV/EHU UFI11/23, the 7th European Union Framework Programme (FP7-PEOPLE-2012-IRSES, Project No. 318901), and the US-DOE grant number DE FG03-87ER-45332. A.F.R. acknowledges support from the MICIIN “Ramón y Cajal” Programme and X.B. that from the University of Barcelona.

References

[1] J. Nogués, I. K. Schuller, J. Magn. Magn. Mat. 192 (1999) 203.

[2] M. Bibes, J. E. Villegas, and A. Barthelemy, Adv. Phys. 60 (2011) 5.

Arantxa Fraile Rodríguez1, Miroslavna Kovylina1, Ali C. Basaran2, Rafael Morales3,4, Matthew A. Marcus5, Andreas Scholl5, Ivan K. Schuller2, Xavier Batlle1, and Amílcar Labarta1 [email protected]


[3] V. Skumryev, S. Stoyanov, Yong Zhang, George Hadjipanayis, D. Givord, J. Nogués, Nature 423 (2003) 850.

[4] J. Nogués, D. Lederman, T. J. Moran, and I. K. Schuller, Phys. Rev. Lett. 76, 4624 (1996).

[5] I. V. Roschchin, O. Petracic, R. Morales, Z.-P. Li, X. Batlle, and I. K. Schuller, Europhys. Lett. 71 (2005) 297

[6] R. Morales, M. Vélez, O. Petracic, I. V. Roshchin, Z. P. Li, X. Batlle, J. M. Alameda, and I. K. Schuller, Appl. Phys. Lett 95 (2009) 092503

[7] M.Kovylina, M. Erekhinsky, R. Morales, I. K. Schuller, A. Labarta, and X. Batlle, Appl. Phys. Lett. 98 (2011) 152507.

[8] I. V. Roshchin, O. Petracic, R. Morales, Z.-P. Li, X. Batlle, I. K. Schuller; International Patent Number: 05803831.6 1214 PCT/US2005025129 (2005)

[9] R. Morales, M. Kovylina, I. K. Schuller, A. Labarta, and X. Batlle, Appl. Phys. Lett. 104 (2014) 032401

[10] Y. Henry, S. Mangin, T. Hauet, and F. Montaigne, Phys. Rev. B 73 (2006) 134420

[11] M. Kovylina, M. Erekhinsky, R. Morales, J. E. Villegas, I. K. Schuller, A. Labarta, and X. Batlle, Appl. Phys. Lett. 95 (2009) 152507

[12] Z-P. Li, R. Morales, and I. K. Schuller, Appl. Phys. Lett. 94 (2009) 142503.

Figure 1. Example of element-specific Ni domain configurations in Ni/FeF2 (70 nm) bilayers measured at zero magnetic field and 30 K after zero field cool from a saturated state at 296 K. The initial remanent saturated state (dark contrast) splits into a ramified pattern of small, inverted domains with opposite magnetic orientation (bright contrast).

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Universitat de Barcelona, Departament de Fisica Fonamental, Diagonal 645, 08028 Barcelona, Spain

Nanoparticles (NP) in the extracellular matrix are immediately coated by layers of biomolecules forming a "protein corona". The protein corona gives to the NPs a "biological identity" that regulates the NP-cell interaction. Therefore, the cell uptake of the NPs is strongly affected by the protein corona. For this reason learning to predict the biological identities of NPs based on a partial experimental knowledge is essential to foresee a priori the safety implications of a NP for human health and, more in general, the environment. To this goal we propose a multiscale approach that allows us to predict the protein corona composition based on a partial experimental knowledge. The approach,both theoretical and computational, includes protein-protein (Vilaseca et al.; 2013) and protein- NP interactions, accounting for the physico-chemical properties (i.e., electrostatic and Van der Waals interactions) and the size of the NPs as in the DLVO theory for colloids. We study, by numerical simulations, the competitive adsorption of proteins on a NP suspended in blood plasma as a function of contact time and plasma concentration. We consider the case of silica NPs in a "simplified" blood plasma made of three competing proteins: Human Serum Albumin, Apolipoprotein A1 and Fibrinogen. These proteins are of particular interest because they have a high concentration in plasma, or because they are the most abundant in the corona of silica NPs (Milani et al.; 2014) Our results are compared with experiments made under the same conditions showing that the approach has a predictive power (Vilanova et al.; 2014).

References [1] Djeribi, R., Bouchloukh, W., Jouenne, T.,

Menaa, B. 2012) Characterization of biofilms formation in urinary atheters, Amer. J. Infect. Control., In Press. P.

[2] Vilaseca, P., Dawson, K.A., Franzese, G. (2013) Understanding and modulating the competitive surface- adsorption of proteins, Soft Matter, 9, 6978.

[3] Milani, S., Vilanova, O., Dawson, K.A., Franzese, G., Rädler, J. (2014) The Protein Corona in a Three Component Model Plasma, In Preparation.

[4] Vilanova, O., Milani, S., Dawson, K.A., Rädler, J., Franzese, G. (2014) Theoretical and Numerical Predictions Compared to Experiments for Silica Nanoparticles in a Three Component Model Plasma, In Preparation.

Giancarlo Franzese


Institut de Bioenginyeria de Catalunya (IBEC), c/ Baldiri i Reixac 15-21, Barcelona, Spain

Electric polarization, represented by the dielectric

constant, r, is an intrinsic property of matter that plays a crucial role in many fields, from materials science and information technology to biology. It is inherently linked to charge storage/transport, it influences light-matter interaction, and it allows for material identification. In biology, dielectric constant modulates the electrostatic interaction between biomolecules and it influences their shapes. In particular, it is key in DNA interaction with effector proteins, DNA bending, DNA packaging, etc. Yet, quantifying local dielectric properties at the nanoscale using scanning probe techniques has been a long-standing challenge because the dielectric signal of nano-objects is extremely weak, dominated by non-local contributions and tip/sample geometrical artefacts. In this communication we will review our recent results using scanning probe techniques, namely, current-sensing atomic force microscopy (C-AFM) [1,2] and electrostatic force microscopy (EFM) [3,4,5]. By combining low-noise detection with quantitative numerical analysis of the tip-sample capacitance and capacitance gradient, respectively, we show that both techniques precisely measure the local dielectric constant with nanoscale lateral resolution. By probing the dielectric constants of 10 nm-radius nanoparticles with ultraweak polarization forces (sub-picoNewton resolution) and using them as the fingerprints of the materials, we were able to recognize nano-objects of identical shape but different chemical composition [3], which would be impossible to distinguish from topography. The long-range nature of polarization forces enabled us to identify the sub-surface material

composition [3] and to experimentally resolve the dielectric constant of DNA [4] - remained unknown so far owing to the lack of experimental tools able to access it - in a natural condensed state inside single viruses. In contrast to the common assumption of low-polarizable behavior like

proteins (r r ∼ 2–4), we found that the DNA

dielectric constant is r r ∼ 8, considerably higher

than the value of r r ∼ 3 found for capsid proteins. State-of-the-art molecular dynamic simulations confirmed our experimental findings, which result in sensibly decreased DNA interaction free energy than normally predicted by Poisson–Boltzmann methods [4]. Finally, dielectric quantification can also be extended to liquid environment [5], which will allow for the study of electrochemical and biological systems in liquid media.

References [1] Fumagalli, L., Ferrari, G., Sampietro, M., Gomila,

G. Appl. Phys. Lett. 2007, 91, 243110. [2] Fumagalli, L., Ferrari, G., Sampietro, M., Gomila,

G. Nano Lett. 2009, 9, 1604. [3] Fumagalli, L., Esteban, D. Cuervo, A, Carrascosa,

J.L., Gomila,G. Nature Mater. 2012, 11, 808. [4] Cuervo, A., Dans, P.D., Carrascosa, J.L., Orozco,

M., Gomila, G., Fumagalli, L. PNAS 2014, 3624 [5] Gramse, G.; Edwards, M. A.; Fumagalli, L,

Gomila, G. Appl. Phys. Lett. 2012, 101, 213108.

Laura Fumagalli [email protected]


1Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden,

01062 Dresden, Germany 2NaMLab GmbH, 01187 Dresden, Germany

3Center for Advancing Electronics Dresden (CfAED), TU Dresden,

01062 Dresden, Germany

Since silicon nanowire (SiNW) based field effect transistors (FETs) were first introduced for pH and bio sensing, [1] diverse configurations of nanowires based sensor devices have been demonstrated to allow the label-free detection of proteins [2], DNA [3], viruses [4], ions [5] and gases [6]. Therefore, using such systems a specific detection of - among others - medically relevant data is possible. Compared to enzyme-linked immunosorbent assay (ELISA) [7], the commonly applied technique for biodetection purposes, results may be obtained much quicker and with lower detection limits.

Here, we present an approach towards the assembly of SiNW based sensory devices made from bottom-up grown SiNWs (see Fig. 1 A). Introducing well-defined Schottky barrier contacts between electrodes and SiNWs allows on/off current ratios of up to 106 and using parallel arrays of SiNWs enables on-currents of over 500 µA at a source drain voltage of 0.5 V. [8]

Furthermore, we implement the SiNW FETs into a biocompatible microfluidic setup for measuring pH changes and determining the optimum working regime of our devices. We also demonstrate the immobilization of aptamer bio receptor molecules on the sensor surface to obtain a bio sensor specific for the blood coagulation protein thrombin with a detection limit in the picomolar range (see Fig. 1 B). And we show how digital droplet logic can be fruitfully combined with our sensor platform to obtain a setup which can provide information

about many separate droplets, i. e. experiments, within a very short time (see Fig. 1 C).

References [1] Y. Cui et al., Science, 293 (2001) 1289. [2] W. U. Wang et al., Proc. Natl. Acad. Sci. USA,

102 (2005) 3208. [3] J. Hahm et al., Nano Lett., 4 (2004) 51. [4] F. Patolsky et al., Proc. Natl. Acad. Sci. USA,

101 (2004) 14017. [5] M. Wipf et al., ACS Nano, 7 (2013) 5978. [6] F. Demami et al., Sensor Actuat. B-Chem., 170

(2012) 158. [7] E. Engvall et al., Immunochemistry, 8 (1971)

871.

[8] S. Pregl et al., Nano Res., 6 (2013) 381. Figure 1. Parallel SiNW arrays in-between interdigitated finger electrodes. B: Schematic drawing of the applied silane based immobilization of aptamers specifically binding thrombin. A second (fluorescence labeled) aptamer is used to realize a sandwich assay. C: Digital droplet logic assembly for multi droplet sensing experiments.

Andreas Gang1,

Sebastian Pregl1, Felix Zörgiebel1, Lotta Römhildt1, Claudia Pahlke1, Julian Schütt1, Walter Weber2,3, Thomas Mikolajick2,3, Larysa Baraban1 and Gianaurelio Cuniberti1,3 [email protected]


ALBA Synchrotron Carretera BP 1413, de Cerdanyola del Vallès a Sant Cugat del Vallès, Km. 3,3 08290 Cerdanyola del Vallès, Barcelona, Spain

ALBA is the Spanish third generation synchrotron light source, located in Cerdanyola del Vallès, near Barcelona, in operation since 2012. The accelerator complex, consisting of a 100 MeV LINAC, a full-energy booster and the 3 GeV storage ring, provide photon beams in a wide spectral range, fed to beamlines devoted to different experimental techniques. ALBA has at the moment seven operational beamlines, whereas two more are starting the construction process. The total capacity amounts to ca. 30 beamlines, which should gradually be built along the next years. Synchrotron light is an extremely powerful tool, suitable for investigation of micro- and mesoscopic features of materials, which can then be related to relevant macroscopic behaviors. Among the very wide range of application areas, some of the techniques available at ALBA are particularly suited for the characterization of nanomaterials. This work provides a summary description of the ALBA facility, with particular emphasis on those techniques and beamlines applicable to Nanoscience and some illustrative examples of experiments run therein.

G. García and E. Pellegrin


1Max-Planck-Institut fur Mikrostrukturphysik, Halle, Germany;

2Donostia International Physics Center, Donostia - San Sebastian, Spain;

3Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Germany;

4Institut für Theoretische Physik, Universität Heidelberg, Germany;

5Tomsk State University, Russia

In this work using first-principles Green's function approach we study magnetic properties of the magnetic binary topological insulators Bi2Se3, Bi2Te23 and Sb2Te3 doped with 3d transition metals, in bulk and at the surface. We analyze the magnetic phase for each dopant, the exchange interaction, the Curie temperature and the Bloch spectral-function. To study the magnetic interaction at the surface we also consider a system consisting of a topological insulator with an array of magnetic adatoms interacting with the electronic surface state. We find that the indirect coupling of the magnetic impurities results in a ferromagnetic ordering of the magnetic moments and is also responsible for the unusual linear dispersion of the surface magnons. Developing a 2D model we analyze the electron-magnon interaction and we observe that it renormalizes the electron energy spectrum. The renormalized spectrum is nonlinear and can be characterized by a negative effective mass of electrons and holes for any k≠0. We conclude that the electron velocity near the Dirac point depends on the electron-magnon coupling.

References

[1] Phys. Rev. B 89, 165202 (2014). [2] Phys. Rev. B 89, 075103 (2014)

Figure 1. Renormalized electron energy spectrum.

Maia García. Vergniory1,2, L. Chotorlishvili3, A. Ernst1, V. Dugaev3, A. Komnik4, M. M. Otrokov2,5, E. V. Chulkov2,5 and J. Beradkar3


Walter Schottky Institut & Physik-department, Technische Universität München, Germany

The development of the future generation of neuroprosthetic devices will require the advancement of novel solid-state sensors and actuators with a further improvement in the signal detection capability, a superior stability in biological environments, and a more suitable compatibility with living tissue. To date, interfacing of living cells and tissue with solid-state electronic devices has mainly been based on conventional silicon technology, in particular using Si metal-oxide-semiconductor field-effect transistor (MOSFET) structures. However, some of the drawbacks associated with this technology, such as its limited stability in aqueous environments and a relatively high electrical noise, have triggered the study of alternative materials and technologies. In this respect, SGFETs based on Si-nanowires, AlGaN/GaN heterostructures, H-terminated diamond, carbon nanotubes and, more recently, graphene have been investigated as sensing devices. Among these materials, graphene is a particularly attractive candidate for bioelectronic applications, due to its remarkable physical and chemical properties. The extremely high charge carrier mobility in graphene leads to a field-effect transistor (FET) performance that is superior to most known semiconductors. Since the first isolation of graphene in 2004, it has been recognized that the outstanding properties of this material could provide game-changing benefits in the development of highly sensitive sensors for advanced applications like biosensing or the detection of single molecules. Currently, graphene devices have been successfully used in several demanding biosensing applications, such as the detection of cell action potentials, protein adsorption, as well as the amperometric detection of different substances

This contribution will provide an overview on graphene based solution-gated field-effect transistors (G-SGFETs) and their application in biosensing and bioelectronics. We will first discuss the science and technology of SGFETs based on CVD graphene, comparing the performance of these devices with other competing technologies. Further, we will demonstrate a versatile route for the functionalization of graphene SGFETs aiming at the introduction of specific sensing mechanisms. Finally, we will report on the detection of action potentials of cells using graphene SGFETs. The high sensitivities of G-SGEFTs, combined with their biocompatibility and the possibility to use flexible substrates could pave the way for a new generation of neuroprosthetic devices, such as retinal implants.

Jose A. Garrido, Lucas Hess, Benno Blaschke, Max Seifert and Martin Lottner [email protected]


Interdisciplinary Laboratories for Advanced Material Physics (i-LAMP) & Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore di Brescia, Via dei Musei 41, 25121 Brescia, Italy

Nanoparticles (NP) such as TiO2, and Ag are promising alternatives to conventional materials [1,2,3] for the antimicrobial activity that has a wide range of important applications in medicine, water disinfection, and consumer products [3,4,5]. In this scenario, a big challenge is the synthesis and application of NP [6,7] to find effective control measures for reducing the incidence of healthcare-associated infections (HAI). HAI have become a global threat [8] due to the emergence and dissemination of microbial pathogens resistant to most antimicrobial agents available (extensively drug-resistant or totally drug-resistant phenotypes) [9,10]. Indeed, an estimated 20% to 40% of HAI have been attributed to cross infection via the hands of healthcare personnel, contaminated indirectly by touching contaminated environmental surfaces. [11] Besides the strict adhesion to hand-hygiene practices and classical environmental cleaning procedures, the development of antimicrobial surfaces/coatings characterized by a long-lasting microbicidal effect to be applied in high-touch hospital devices (e.g. buttons or handles), is still a promising but not yet realized approach [10,11]. The challenge is directly related to the physical behavior of the NP (e.g. adhesion to surface determined by the NP-surface interactions) that would be the active material. To date, the synthesis of Ag NP is largely based on wet chemical reduction, [4] posing several problems such as the solvents and synthesis process costs to avoid the NP aggregation in solution, the NP adhesion to metal surfaces requiring further functionalization. An alternative route to wet NP synthesis is the supersonic cluster beam deposition (SCBD), [12,13] based on the pulsed ablation of the material to be deposited and the subsequent formation of a NP beam. The

method has also been shown to produce NP with mixed chemical composition, [13] allowing the combination of different elements to engineer the material properties. To our knowledge, this method has not been applied yet to synthesize Ag NP films with antimicrobial properties. In the present work, we obtain for the first time Ag NP films via SCBD. The films (thickness can be tuned according to the experimental needs) are deposited at room temperature RT in medium vacuum (base pressure 1 x 10-6 mbar) conditions by SCBD [12,13] directly on microscope slides (SLG). Atomic force microscopy (AFM) of the as-deposited NP films is shown in Figure 1a. The NP are homogeneously distributed (rms roughness < 1 nm) with no coarsening over the entire covered area (~15 cm2). XRD data (not shown) indicate that the NP are crystalline with a predominant (111) surface orientation and an average diameter of 7.4 x 0.1 nm. The NP density is 1.15±0.04 x 1011 NP/cm2. Since the film density depends on the deposition time, it can be easily tuned from a few percent of the surface area up to a single layer and beyond. The chemical state of the NP have been studied by Auger and X-Ray photoemission spectroscopy (XPS). A comparison of normalized MNN Auger spectra for the Ag NP film (curve b) and from a polycrystalline, metallic Ag reference (curve a), is shown in Figure 1b together with their difference (curve (b-a)). Spectrum b) presents a broader lineshape, reflected in the difference peak at 351±0.5 eV, while the feature at 357±0.5 eV is due to the appearance of a new structure: both consistent with the presence of Ag+ ions. [14] The oxidation of the as-deposited NP film is confirmed by XPS data (not shown). Hence the NP are in a Ag2O oxidation state. This is a required condition

Luca Gavioli, E. Cavaliere, S. De Cesari, G. Landini, E. Riccobono, G. M. Rossolini and L. Pallecchi

[email protected]


for NP to release Ag+ ions, which has been recently proposed as the more relevant mechanism with respect to the role of the NP size giving rise to the bactericidal activity of the NP.[6] Ag NP films were found to exert a potent and broad-spectrum bactericidal activity, which was demonstrated both for reference strains and for a collection of clinical strains that exhibited extensively drug-resistant phenotypes and belonged in high-risk hyperepidemic clones(see Figure 2 and references [15,16,17,18] for strains characteristics). In particular, 24 hours of exposure to Ag NP films were able to reduce viable bacterial loads by more than 4 log with the majority of strains tested, including representatives of both Gram positive and Gram negative pathogenic species. The highest susceptibility was observed with members of the family Enterobacteriaceae (i.e. E. coli and K. pneumoniae), which are normal constituents of the intestinal microbiota and among the most common causes of HAI.[8] Interestingly, Ag NP films could almost completely sterilize a high inoculum (i.e. ~1 x 107 Colony Forming Units [CFU]) of extensively drug-resistant clinical strains producing two of the most worrisome resistance mechanisms recently emerged in enterobacteria and capable of pandemic dissemination, such as the NDM- and KPC-type carbapenemases. An overall strong bactericidal activity was also demonstrated against reference and clinical strains of P. aeruginosa and A. baumannii, including representative of extensively drug-resistant high-risk clones (Figure 2). Those microorganisms are major opportunistic pathogens in the hospital setting, with high propensity to evolve extensively drug-resistance and even totally drug-resistance phenotypes and to survive for long periods in the hospital environment (accounting for the occurrence of nosocomial epidemics through, contaminated taps, sinks or either antiseptic solutions).[11] In conclusion we have demonstrated the realization of a Ag NP film with extremely controlled thickness and NP size directly on a substrate surface through a simple technique, SCBD. Such films present a high and broad-spectrum bactericidal activity that could be related to the oxidation state of the Ag NP. In perspective, the SCBD ability to modify the NP chemical composition will open large possibilities

for tailoring the active material to optimize the precious metal amount, expanding the spectrum of antimicrobial activity, tailor the adhesion to metal surfaces to obtain a long lasting, low cost antimicrobial film.

References [1] Boisselier, E., Astruc, D. Chem. Soc. Rev. 38

(2009) 1759. [2] Liu, C., Burghaus, U., Besenbacher F., Wang, Z.

L. ACS Nano 4 (2010) 5517. [3] Li, Q. Mahendra, et al. Water research 42

(2008) 4591. [4] Badireddy, A. R., et al. Environ. Sci. Technol. 41

(2007) 6627. [5] Seil, J. T., Webster, T. J. Inter. J. Nanomedicine

7 (2012) 2767. [6] Xiu, Z. M., Zhang, Q. B., Puppala, H. L., Colvin,

V. L., Alvarez, P. J. J.Nano Letters 12 (2012) 4271.

[7] Guzman, M., Dille, J., Godet, S. Nanomedicine-Nanotech. Biol. Med. 8 (2012) 37.

[8] European Centre for Disease Prevention and Control (ECDC). Point prevalence survey of HAI and antimicrobial use in European acute care hospitals 2011-2012.

[9] Boucher, H. W., et al. J. Clin. Infect. Dis. 48 (2009)1.

[10] Weber, D. J., Rutala, W. A. Am. J. Infect. Control 41 (2013) S31.

[11] Weber, D. J., Anderson, D., Rutala, W. A. Curr. Opin. Infect. Dis. 26 (2013) 338.

[12] Barborini, E., et al. Appl. Phys. Lett. 81 (2002) 3052.

[13] Chiodi, M., et al J. Phys. Chem. C 116 (2012) 311.

[14] Giallongo, G. et al. Plasmonics 6 (2011) 725. [15] D'Andrea, M. M., et al. J. Clin. Microbiol. 49

(2011) 2755. [16] Giani, T., et al. J. Clin. Microbiol. 47 (2009)

3793. [17] Nigro, S. J, Hall, R. M. J. Antimicrob.

Chemother. 67 (2012) 335. [18] Riccio, M. L., et al. Antimicrob. Agents

Chemother. 49 (2005)104.

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Figure 1. a) AFM image of the as-deposited Ag NP film, showing the uniformity at microscopic scale. In the inset, high resolution image where the NP size can be appreciated. b) Auger spectra of the as-deposited NP film (curve (b), red dots) and metallic polycrystalline Ag reference (curve (a), black dots), with the difference spectrum plotted in the bottom to highlight the oxidation state of the NP film. Figure 2. The microbicidal effect is calculated as log reduction of viable cells compared to control, after 24 hours of exposure.

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1Centro Nacional de Microelectrónica (CNM-CSIC), Campus UAB,

Cerdanyola del Valles, Barcelona, Spain 2Instituto de Ciencias de Materiales de Barcelona (ICMAB-CSIC),

Campus UAB, Cerdanyola, Spain 3Nagoya Institute of Technology, Gokiso, Showa, 466-8555 Nagoya, Japan

Currently, the most promising technique to produce graphene at wafer-scale for industrial purposes seems to be epitaxial growth either by chemical vapor deposition (CVD) on a metallic substrate or by heating a SiC substrate up to the graphitization temperature. In the first case, because the metallic film is electrically conducting, the graphene film needs to be transferred to an insulating substrate for applications based on electronic transport. In the second case, the graphene can be directly used on the insulating SiC surface. Silicon sublimation from the SiC causes a carbon rich surface that nucleates an epitaxial graphene layer. The graphene growth rate was found to depend on the specific polar SiC crystal face: graphene forms continuous layer on Si-face (Fig 1a), while under certain growth conditions, graphene flakes can be obtained on the C-face the surface (Fig 1b). In both case, resulting surface is composed of SiC steps with micrometer wide terraces (Fig 1a). It has been shown that the graphene grown on the terraces sidewall is of poor quality. Then, lithography processes must be aligned with the terraces. In the case of graphene flakes on C-Face, the flake must be localised and lithography must be done based on the flake position. As a consequence, most of lithography steps must be done using electron beam lithography. An alternative to this standard technique is to growth the graphene on pre-patterned wafers with a template. A material able to withstand high temperature must be used as mask such as AlN (Fig 1c) [1] or Si3N4. On the other hand, nanoribbons on SiC combine the high mobilities of graphene on SiC with a gap opening capability thanks to quantum confinement observed in nanoribbons. Typically, the gap energy separation between the sub-bands is inversely

proportional to the ribbon width, as well as on the edges type of the ribbons. Ribbons obtained by plasma etching after ebeam lithography typically create rough edges that cause electron scatters and strong localization effects appear. As an alternative to ebeam lithography, Local Anodic Oxidation (LAO) has been tested to define nanoribbons [2-3], as Silicon Carbide can be oxidized forming a SiO2 dielectric layer. An electrically isolated narrow ribbon of graphene can be drawn in such way. However, the best way to generate high performances nanoribbons on SiC is to use selective growth on crystal facets of SiC [4]. Besides the on-axis facets, SiC has other crystal facets with low crystal indies such as the SiC "sidewalls" that connect the terraces on the on-axis wafer surface. These low-index facets grouped as (110n) and (112n) have been used to selectively growth high performances graphene nanoribbons [4]. The facets are created by standard lithography and RIE etching. Then, special growth parameters can be found to get growth only on the facet, the nanoribbon width being defined by the etched sidewall depth.

References [1] N. Camara, G. Rius, J.-R. Huntzinger, et als ,

Applied Physic Letters 93, 123503 (2008) [2] M. Lorenzoni, B. Torre, Applied Physics Letters,

103, 163109 (2013) [3] G. Rius, N. Camara, P. Godignon, F. Perez-

Murano, J. Vac. Sci. Technol. B (2009) Vol. 27 (6), 31493152

[4] M. Sprinkle, M. Ruan, Y.Hu, J. Hankinson, M. Rubio et als, Nature Nanotechnology 5, 727-731 (2010).

P. Godignon1, M. Wojtaszek1, N. Mestres2, G. Rius3 and F. Perez-Murano1


Figure 1. (a) graphene on SiC Si-face, (a) graphene on SiC C-face (c) graphene grown in AlN template, (d) graphene lithographed by LAO.

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Aixtron Ltd - Anderson Road, Swavesey, Cambridge, CB24 4FQ, United Kingdom

In the past few years, graphene has attracted the attention of a considerable number of scientists from different areas. The outstanding properties of this 2D material which include, high carrier mobility, electrical conductivity, transparency, thermal conductivity and mechanical strength, make graphene a good candidate for novel optoelectronic devices. The commercialization of graphene still remains challenging, especially for high-end applications like complementary metal oxide semiconductors (CMOS) circuitry where high quality and high throughput are required. From the available growth techniques, which play an important role on the materials properties, chemical vapour deposition (CVD) has proved to meet the requirements for high-end applications and to provide an easy integration with current and future CMOS technology. Here we present some recent advances on CVD graphene technology, discussing the growth process scalability from 2” to 12”wafers size as well as presenting some future challenges for other 2D materials.

Gonçalo Gonçalves, Bingan Chen, Alex Jouvray, Nalin Rupensighe and Ken Teo


1 CIC nanoGUNE, Donostia-San Sebastian, Spain

2 I.N.T.I.-CONICET and ECyT-UNSAM, San Martin, Argentina

3 IKERBASQUE, Basque Foundation for Science, Bilbao, Spain

4 ECE Dept. and Beckman Institute, U. of Illinois at Urbana-Champaign, Urbana, USA

5 EHU/UPV, Donostia-San Sebastian, Spain

Scattering-type scanning near-field optical microscopy (s-SNOM) is a powerful optical technique for nondestructive spectroscopic imaging with deep subwavelength resolution [1]. In s-SNOM, images are recorded by scanning a sharp illuminated probe along the sample surface and detecting the backscattering. This scattering depends on the near-field interaction between the probe and the sample, thus revealing the dielectric properties of the sample in the image contrast. While s-SNOM has demonstrated the ability of quantitative analysis of such images for samples with structure varying in two dimensions [2], the elucidation of sample structure in all three dimensions (3D) has proved elusive. The main obstacle to inferring the 3D sample structure from s-SNOM images is the complicated nature of near-field interaction that intermixes (couples) the dielectric properties of sample constituents/features with their distance to the tip. Thus the same image contrast could result from the variation of the dielectric permittivity of the feature or its depth below the sample surface, i.e. from the sample geometry. The lack of simple image interpretation method resulted in s-SNOM being traditionally regarded as a technique for surface studies. In this work we break the traditional view at s-SNOM and open the door to the third dimension for near-field techniques by introducing and providing the first experimental demonstration of a method for performing a rapid recovery of the thickness and permittivity of simple 3D objects, such as thin films and polymer nanostructures [3]. This is accomplished by taking advantage of the near-field data recorded at multiple harmonics of

the oscillation frequency of near-field probe as depicted in Figure 1. A complete set of such harmonics serves as a proxy for an approach curve that measures the near-field interaction as a function of tip-sample distance. Thus multiple harmonics of the demodulated signal encode information about the volumetric composition of the sample. To recover this volumetric information, we developed a novel nonlinear model that describes the near-field interaction of the s-SNOM tip with a film deposited on a substrate. The key advantage of our model is that it allows for an analytic inversion of the associated scattering problem with respect to the sample permittivity, parameterized by a single depth/thickness variable. The correct film thickness is then obtained by enforcing the consistency of the results derived from different harmonics of the scattered signal. Mathematically, this formulates a simple one-dimensional minimization problem that decouples the dielectric properties from the sample geometry, thus allowing for the unique interpretation of near-field images. In conjunction with the simplicity of obtaining the necessary data (the signal harmonics are routinely recorded as a part of the background suppression in s-SNOM) our technique presents a humble, practical method of recovering the subsurface sample structure from near-field measurements. Our work enables the quantitative nondestructive nanoscale-resolved optical studies of thin films, coatings and functionalization layers, as well as the structural analysis of multiphase materials and other samples in which the topography does not correlate with the chemical or optical properties. It

A.A. Govyadinov1, S. Mastel1, F. Golmar2, A. Chuvillin1,3, P.S. Carney4, and R. Hillenbrand1,3,5

[email protected]


opens new frontiers for chemometrics, materials and bio sciences and represents a major step towards the further goal of the near-field nanotomography.

References [1] T. Taubner, R. Hillenbrand, and F. Keilmann,

Appl. Phys. Lett. 85, 5064 (2004), [2] A. Govyadinov, I. Amenabar, F. Huth et al, J.

Phys. Chem. Lett. 4, 1562 (2013), [3] A. Govyadinov, S. Mastel, F. Golmar et al, ACS

Nano, in Just Accepted (2014).

Figure 1. Schematics of the s-SNOM experiment and the conceptual representation of the reconstruction

procedure that yields the sample structure. The field scattered by an oscillating AFM tip is detected

interferometrically and demodulated at higher harmonics of the tip oscillation frequency. By scanning the sample

surface, a set of near-field images is recorded. A mathematical inversion procedure is then applied at each pixel to

recover the sample structure, i.e., thickness (represented by red curve) and dielectric permittivity (represented by

fill color) of the sample layer.

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1UMR5819 CEA-CNRS-UJF SPrAM, CEA-Grenoble/INAC/SPrAM 17 rue des Martyrs 38054

Grenoble Cedex 9, France 2IEMN-CNRS UMR8520 Avenue Poincaré CS 60069 F-59652 Villeneuve d'Ascq

Cedex, France 3Department of Computational Physics, IFM, Linköping University,

S-58183 Linköping, Sweden

Long, conductive molecular wires have attracted Kelvin Probe Force Microscopy (KPFM) is a powerful tool of characterization in the field of organic photovoltaics. By combining KPFM with non-contact AFM (nc-AFM) under ultra-high vacuum, topography and surface contact potential (CPD) contrasts can be simultaneously mapped with an exceptional level of resolution. In the case of organic donor-acceptor (D-A) blends, KPFM has been widely used this past decade to map surface photo-voltages (SPV), paving the way for local investigations of charge generation and transport mechanisms at the nanometer scale. However, most of times, achieving a sub-10nm resolution [1] by nc-AFM/KPFM in bulk hetero-junction (BHJ) thin films remains a challenge. Moreover, carrying a quantitative analysis of the SPV contrasts is hardly achievable in the case of three-dimensional interpenetrated D-A networks with nano-phase segregated domains. Last, another issue is related to the eventuality of non-conventional effects (such as tipinduced surface polarization) in the short range regime, which can contribute to the local CPD contrasts at the sub-10nm scale [2]. In this communication, we address these issues by analyzing KPFM images acquired on new model donor-acceptor organic architectures, with better defined morphologies than the ones displayed by more conventional BHJ blends. First, a donor-acceptor blend based on a first generation dendrimer [3] (FG1) and [70]PCBM has been used as a model system to investigate the influence of the tip-surface interaction regime on the local CPD and SPV contrasts. Thanks to the

liquid crystalline properties of the electron donor FG1, the D-A phase separation can be tuned via in situ sample annealing. FG1: [70]PCBM blends can be obtained on ITO/PEDOT:PSS substrates, for which [70]PCBM clusters are buried in the sub-surface of a matrix of self-assembled pi-stacked FG1 molecular wires. These extremely flat samples constitute model photovoltaic systems for high resolution KPFM investigations, firstly thanks to the highly homogeneous nature of the surface layer, which reduces the risk of cross talk effects between the topographic and CPD channels. The photovoltaic effect is moreover completely reversible (i.e. the CPD returns completely to its initial value after switching the illumination off), which indicates the absence of charge trapping effects in these blends. Thanks to these remarkable properties, we carried out a complete analysis of the influence of the tip-surface interaction regime (from the long range to the short range) on the topographic, dissipation, in-dark CPD and SPV contrasts, with the support of electrostatic numerical simulations. Series of images were acquired on the same location by varying the nc-AFM parameters, which confirm that the optimal lateral resolution is achieved near the onset of the apparition of a contrast in the damping images. In-dark CPD contrasts over sub-surface [70] PCBM clusters are consistent with dipoles at the D-A interfaces, as predicted from integer charge transfer (ICT) models for FG1: [70]PCBM. These results also confirm that sub-10nm SPV contrasts can be achieved, and the comparison between damping, in-dark CPD and SPV images allows excluding the existence of artifacts. Last, a

B. Grevin1, F. Fuchs1, T. Mélin2, M. Linarès3, C. de Vet1, F. Caffy1 and R. Demadrille1 [email protected]


remarkable dependence of the SPV magnitude with respect to the tip-surface distance is evidenced, and tentatively attributed to a local enhancement of the electromagnetic field at the tip apex. In a second part, we apply another approach to build model D-A architectures for local SPM investigations, by using self-assembled donor-acceptor dyads. A new generation of D-A dyads based on covalently coupled perylene diimide and fluorenone-terthiophene units is studied in the form of selfassembled monolayers on highly oriented pyrolitic graphite (HOPG). By confronting nc-AFM and scanning tunneling microscopy (STM) images to the results of molecular mechanics and dynamics simulations, we show that edge-on donor-acceptor lamella grow on a buffer layer of self-assembled face-on molecules, which decouples the edge-on stack from the underlying substrate. The analysis of KPFM data recorded under different optical power and wavelength demonstrate that surface photovoltages can be detected at the scale of one monolayer. The charge photo-generation and transfer to the substrate is analyzed and a clear relationship between the molecular assembly and its photovoltaic behavior is established. This work paves the way for local investigations of the optoelectronic properties of DA dyads, triads, block copolymers and PV architectures down to the level of a single molecular layer.

References [1] SE. J. Spadafora, R. Demadrille, B. Ratier, and

Benjamin Grévin, Nano Lett. 10, (2010) 3337. [2] E. J. Spadafora, M. Linares, W. Z. Nisa Yahya, F.

Lincker, R. Demadrille and B. Grevin, Appl. Phys. Lett. 99, (2011) 233102.

[3] F. Lincker, B. Heinrich, R. De Bettignies, P. Rannou, J. Pécaut, B. Grévin, A. Pron, B. Donnio and R. Demadrille, J. Mater. Chem. 21, (2011) 5238.

Figure: nc-AFM/FM-KPFM (UHV,300K) image of a FG1:[70]PCBM thin film blend recorded in dark. (a) Topography (b) Dissipation (c) CPD. Sub-surface [70]PCBM clusters covered by self-assembled FG1 molecular wires appear as bright spots in the CPD image, reflecting the existence of dipoles at the recessed D-A interfaces.

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1Depto. Física de Materiales, Universidad del País Vasco, UPV/EHU, Spain

2IKERBASQUE, The Basque Foundation for Science, Bilbao, Spain

3IFIMUP, IN-Institute of Nanoscience & Nanotechnology, Depto. Fisica e Astronomia,

Universidade do Porto, Porto, Portugal 4Faculty of Radiophysics, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine

5Materials Science Division, Argonne National Laboratory, Argonne, Illinois, USA

6Department of Physics, Oakland University, Rochester, Michigan, USA

When the in-plane bias magnetic field acting on a flat soft magnetic particle (dot) is smaller than the saturation field, there are two stable competing magnetization configurations of the dot: vortex and quasi-uniform state [1]. To measure the microwave absorption in a two dimensional array of in-plane magnetized magnetic dots we used a technique of vector network analyzer ferromagnetic resonance (VNA-FMR) [2]. The investigated magnetic dot array (patterned film area is 5x5 mm2) was composed of circular permalloy (Ni80Fe20 alloy) dots having the radius 150 nm and thickness 14 nm. The edge-to-edge interdot distance was 300 nm that guarantees absence of the interdot magnetostatic interaction. We measured microwave absorption properties of the dot array in the frequency range 1-8 GHz when bias magnetic field was varied in the region of the magnetization state bi-stability in the range 0 – 600 Oe (Figure 1). It was found that the microwave absorption properties of magnetic dots existing in the quasi-uniform and vortex states are qualitatively different [3]. The frequency of the resonance microwave absorption in the quasi-uniform magnetization stable state increases with the increase of the bias field, while in the vortex magnetization stable state it remains practically constant and equal to 7 GHz. For the dots existing in a quasi-uniform and C- stable states [4] a considerable linewidth broadening (up to 2 times, from ~ 300 MHz to ~ 600 MHz, was found when the in-plane bias magnetic field is decreasing from the field of a vortex

annihilation (Han = 450 Oe) to the field of a vortex nucleation (Hn =50 Oe), while for the dots existing in the vortex stable state the absorption linewidth remains practically constant within the whole interval of the bias field variation. The microwave susceptibility of the dots in the quasi-uniform state has a broad maximum in the bias field interval 100-400 Oe and decreases at low and high values of the field, while in the vortex stable state the susceptibility increases with the bias field increase and reaches a maximum value at the vortex annihilation field. Due to the hysteresis in the dot magnetization stable states and substantially different microwave absorption properties in the quasi-uniform and vortex states (that can co-exist at the same value of the bias magnetic field) it would be possible to use arrays of non-interacting magnetic nanodots for the development of dynamically reconfigurable microwave absorption materials, where the microwave properties of the patterned materials depend on the magnetization history and could be changed dynamically through a fast remagnetization [5].

References

[1] K.Y. Guslienko, J. Nanosci. Nanotechn., 8 (2008) 2745.

[2] Y. Kobljanskyj, G.A. Melkov, K.Y. Guslienko, V. Novosad, S.D. Bader, M. Kostylev, and A.N. Slavin, Sci. Reports, 2 (2012) 478.

Konstantin Gusliyenko1,2,

Gleb Kakazei3, Yurii Kobljanskyj4, Gennadii Melkov4, Valentyn Novosad5, Andrei Slavin6 [email protected]


[3] K.Y. Guslienko, G.N. Kakazei, Y.V. Kobljanskyj, G.A. Melkov, V. Novosad, and A.N. Slavin, New J. Physics, in press (2014).

[4] G.A. Melkov, Y. Kobljanskyj, V. Novosad, A.N. Slavin, and K.Y. Guslienko, Phys. Rev. B, 88 (2013) 220407.

[5] R. Verba, V. Tiberkevich, K. Guslienko, G. Melkov, and A. Slavin, Phys. Rev. B, 87 (2013) 134419.

Figure 1. Experimental VNA-FMR microwave absorption lines of a square array of cylindrical permaloy dots (the dot radius is 150 nm, the dot thickness is 14 nm, edge-to-edge interdot distance is 300 nm) measured at four different points ((1)-(4)) on the static magnetization hysteresis loop of the array shown in the inset. The marked fields Hn, Han are the magnetic vortex nucleation and annihilation fields, respectively. Points (2), (3), and (4) (H = 520, 350, 90 Oe) are situated on the upper branch of the hysteresis loop corresponding to the quasi-uniform stable state of the dots, while the point (1) (H = 350 Oe) is situated at the lower branch of the hysteresis loop corresponding to the vortex stable state of the dots. Note that the absorption curves corresponding to points (1) and (3) are taken at the same magnitude of the in-plane bias magnetic field H = 350 Oe.

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Institute of Physics, University of Tartu, Riia 142, Tartu, Estonia

If we need fibers with nicely circular, ellipsoidal, or even irregular cross-section geometry, we can use sol-gel technology.[1] Additionally, hollow fibers can also be prepared. M. Aizawa et al. [2] did embarks follow such structures, denoted as capillaries or microtubes, preparation methods. Curing processes affording transformation of liquid threads into solid material have achieved technological importance. In our recent work [3,4,5] we using sol-gel transition (solidification; curing) of metal-alkoxide liquid threads for the preparation of the oxide ceramic fibers and microtubes. We started from fibers, designated their mechanical properties [3], and then modified the method for microtubes [4]. The method is founded on using precursors including of sub-crystalline 1-2 nm metal-oxo cores, disclosed as a product of reaction between metal-oxo-alkoxides and water. The cores without stabilizing shells are used as blocks to build up the walls of the tubes. The chemical process occurs as a self-assembly of particles, while released alcohol remains to fill the core of the tube and is removed later by evaporation. These experiments tender a solution to the technological problem in the preparation of high quality 10 to 100 μm diameter nanoceramic-microtubes. This presentation is focusing on the collation of curing mechanisms for metalalkoxide-derived liquid threads. Likening the solidification of propoxide and butoxide precursors, we studied the mechanisms of the formation of fine metal oxide fibers or hollow microtubes. These microtubes are auspicious candidate material for catalyst carriers and microreactors, drug delivery, for microbattery applications [6]. If operating under extreme

conditions (high pressure, temperature or plasma), also as pipes in different microfluidic systems [6].

References

[1] S. Sakka; K. Kamiya, Mater.Sci. Res, 17 (1984) 83.

[2] M. Aizawa; Y. Nakagawa; Y. Nosaka; N. Fujii; H. Miyama, Journal of Non-Crystalline Solids, 124 (1990) 112.

[3] K. Hanschmidt; T. Tätte; I. Hussainova; M. Part; H. Mändar; K. Roosalu; I. Chasiotis, Applied Physics A, 3 (2013) 663.

[4] M. Part, T. Tätte, U. Mäeorg, V. Kiisk, G. Nurk, A. Vorobjov, K. Hanschmidt, Invention EP11817521.5 / US13/981276, 31.12.2010.

[5] K. Saal; T. Tätte; M. Järvekülg; V. Reedo; A. Lõhmus; I. Kink, International Journal of Materials and Product Technology, 40(1/2) (2011) 2.

[6] T. Tätte; M. Part; R. Talviste; K. Hanschmidt; K. Utt; U. Mäeorg; I. Jõgi; V. Kiisk; H. Mändar; G. Nurk; P. Rauwel, RSC Adv., 34 (2014) 17413.

[7] M. Part; K. Hanschmidt; J. Jõgi; E. Rauwel; G. A. Seisenbaeva; V. G. Kessler; T. Tätte, RSC Adv., 24 (2014), 12545

Kelli Hanschmidt, Marko Part, Rasmus Talviste and Tanel Tätte [email protected]


Figure 1. Curing process illustration for metalalkoxide precursors.

Figure 2. In laboratory atmosphere as-drawn Zr(OBu)4 and Ti(OBu)4 threads shrinkage of solidification is 30-50 % [6].

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Nihon University, College of Industrial Technology, Dep. of Applied Molecular Chemistry, 1-2-1 Izumi-cho, Narashino, Chiba 275-8575 Japan

Since the first synthesis of nanocomposite hydrogels (NC gels) with a unique organic (polymer)/inorganic (clay) network structure was reported,[1] NC gels have received a great deal of attention as super hydrogels that can overcome many of the serious disadvantages associated with conventional chemically crosslinked hydrogels (OR gels).[2] In particular, NC gels consisting of poly(N-alkylacrylamide)s such as poly(N-isopropylacrylamide) (PNIPA) or poly(N,N-dimethyl acrylamide) (PDMAA), and exfoliated inorganic clay such as hectorite or montmorillonite, have been shown to have extraordinary optical, mechanical, and swelling/de-swelling properties.[3,4] Furthermore, NC gels can be prepared easily at ambient temperature in an aqueous system, providing a variety of shapes, sizes, and surface morphologies, along with novel surface characteristics such as unique sliding friction, ultrahigh hydrophobicity, support for stem cell proliferation, self-healing ability, and non-toxicity, which allows for their use in many new applications.[4-8] Pt nanoparticles (Pt NPs) are currently used in many areas of nanoscience and technology. To date, numerous studies have been reported on the design of noble metal-based nanomaterials including NP-hydrogel composites that fabricated by exploiting the interspatial area between crosslinking points as a nanoreactor or nanocarrier. However, there have been very limited studies on Pt NP-hydrogel composites because it is difficult to prepare a material with fine and well-dispersed Pt NPs immobilized within a hydrogel. Furthermore, since the inherent properties of Pt NPs strongly depend on their size, dispersion, and the supporting material, new nanostructured Pt

materials with tailored morphologies and performances are still greatly desired. Here, we report the synthesis, structure, and properties of a novel hydrogel-based nanostructured Pt material, Pt-NC gel, consisting of ultrafine Pt NPs strongly immobilized within a unique polymer-clay network. [9] Pt-NC gels were synthesized through exfoliated clay-mediated in situ reduction of Pt ions in the NC gel at ambient temperature. [9,10] Pt NPs were trapped on the clay surface, at the edges of the clay nanoplatelets. Ultrafine Pt NPs were also obtained as a stable suspension from the NC gel, without any stabilizing agents. The combination of ultrafine Pt NPs and mechanically tough NC gel may open up new possibilities for designing functional Pt-gel materials

References

[1] K. Haraguchi, T. Takehisa Adv. Mater., 14 (2002) 1120-1124.

[2] K. Haraguchi, Curr. Opin. Solid State Mat. Sci., 11 (2007) 47-54.

[3] K. Haraguchi, H-J. Li, Angew. Chem. Int. Ed., 44 (2005) 6500-6504.

[4] K. Haraguchi, Polym. J., 43 (2011) 223-241. [5] K. Haraguchi, Macromol. Rapid Commun., 32

(2011) 1253-1258. [6] K. Haraguchi, Macromolecules, 45 (2012) 385-

391. [7] N. Kotobuki, K. Haraguchi, J. Biomed. Mater.

Res. A, 101 (2013) 537-546. [8] N. Jing, G. Li, K. Haraguchi, Macromolecules, 46

(2013) 5317-5328.

Kazutoshi Haraguchi [email protected]


[9] K. Haraguchi, D. Varde, Polymer, 55 (2014) 2496-2500.

[10] D. Varade, K. Haraguchi, Langmuir, 29 (2013) 1977-1984.

Figure 1. NC gels with various sphaes, e.g., rod, bulk, film, sheet, and deformations such as knotted and stretched NC gel, compression of NC gels with different clay contnet, and strong resistance against bar-pushing by a thin film of NC gel.

Figure 2. (a) Color changes of the N-NC5 gel kept in an aqueous solution of K2PtCl4 in the dark at 25

oC for 60 h.

(b) show the TEM images of the dried Pt-NC5 gel. The histogram shows the Pt NP size distribution in the Pt-NC5 gel. The inset shows the HR-TEM image, revealing the lattice fringes of crystalline Pt NPs.

Figure 3. Schematic representation of the formation of the Pt-NC gel: (a) Pt ions penetrate the N-NC gel, (b) Pt ions (PtCl2) interact with the silanol groups on the clay surface and are reduced to Pt

0, (c) Pt NPs are formed by

the migration of Pt, and are subsequently trapped on the clay surface.

Figure 4. Catalytic reduction of 4-nitrophenol by NaBH4 in the presence of (a) dried Pt-NC5 gel powder (3.5 mg), and (b) dried Pt NPs (1 mg) obtained in the surrounding solution. The strong UV absorption peak at 400 nm corresponds to the nitrophenolate ions.

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1Department of Chemistry, Faculty of Science, Masaryk University, Kampus Bohunice, Kamenice 5/A14, 625 00 Brno, Czech Republic

2Department of Physical Electronics, Faculty of Science, Masaryk University, Czech Republic

3CEPLANT, R&D Center for Low-cost Plasma and and Nanotechnology Surface Modifications, Masaryk University, Kotlářská 2, 611 37

Brno, Czech Republic

Chalcogenide glasses and theirs thin films or fibres have become attractive nano-materials in optics, optoelectronics, chemistry etc. as optical non-linear elements, memories, micro lenses, waveguids, bio- and chemical-sensors, novel optic materials, etc. Problems of theirs structure, properties, and applications have been reviewed [1]. Even if they are studied extensively using various physico-chemical methods, Raman and IR spectroscopy and/or mass spectrometry [2], etc. the structure is stil not completely resolved. Laser desorption ionization time-of-flight mass spectrometry (LDI TOF MS) is powerful technique to follow the generation of clusters also from various solid inorganic materials (Figure 1, left) and might bring valuable information about solid phase structural fragments. It has has been widely used in our laboratory for the analysis of chalcogenide glasses and their thin films to analyse structural fragments of different chalcogenate glasses , e.g. erbium-doped Ga-Ge-Sb-S glass [3] or atomic switch memory Ge2Sb2Te5 bulk materials and its nano films [4]. In this work, possibilities and limitations of LDI and laser ablation synthesis (LAS) coupled with TOF MS will be illustrated and discussed using variety of examples of various chalcogenide glasses of different composition. For example, Figure 1 (right) shows LDI TOF mass spectrum concerning clusters detected from Ge-Ga-As-S glass doped with erbium. Detected clusters GaSb2SEr + and GaS2Er+ indicate how Er dopant is bound in the glass.

It will also be shown how common MALDI TOF MS instrumentation can be used as a synthetic device, a kind of synthetiser, for LAS synthesis of clusters to follow behaviour of chalcogenide glasses precursors and or theirs components. For example, the generation of new gold tellurides using nano-gold and tellurium as precursors via Laser ablation synthesis (LAS) has been reported recently [5] as well as generation of clusters of gold phosphides [6], gold arsenides [7], gold carbides [8] or ternary Au-Ag-Te clusters [9], for example. Concluding, clusters produced via LDI of chalcogenide glasses and/or via laser ablation synthesis of chalcogenide glasses components and/or precursors and detected by TOF MS help to elucidate the structure of solid chalcogenide glasses. Structural fragments of different chalcogenide glasses will be shown and discussed. The determined stoichiometry of detected clusters might accelerate further development of novel high-tech chalcogenide glass materials with unique properties. Acknowledgements Support of Grant Agency of the Czech Republic (Project No.13-05082S) and project R&D Centre for Low-Cost Plasma and Nanotechnology Surface Modifications CZ.1.05/2.1.00/03.0086 funding by the European Regional Development Fund are acknowledged.

Josef Havel1,2,3 [email protected]


References [1] Jean-Luc Adam and Xiaunhua Zhang (Eds),

Chalcogenide glasses. Preparation, properties and applications, WP Publ. Series in Electronics and Optical Materials: Number 44, Woodhead Publ. Ltd., 2014.

[2] J. Ei-Nakat, I. Dance, K. Fisher, G. Willet. Gas-phase silver chalcogenide ions investigated by laser-ablation Fourier transform ion cyclotron resonance mass spectrometry. J. Chem. Soc. Chem. Commun. 1991, 746.

[3] S. D. Pangavhane, P. Němec, V. Nazabal, A. Moreac, P. Jóvári and J. Havel, Laser desorption ionization time-of-flight mass spectrometry of erbium-doped Ga-Ge-Sb-S glasses , Rapid Commun. Mass Spectrom. 28(11) 1221-1232 (2014).

[4] J. Houška, E. M. Peña-Méndez, J. Kolář, J. Přikryl, M. Pavlišta, M. Frumar, T. Wágner, J. Havel, Laser desorption time-of-flight mass spectrometry of atomic switch memory Ge2Sb2Te5 bulk materials and its thin films, Rapid Commun. Mass Spectrom. 28 (7), 699-704 (2014).

[5] K. Švihlová, L. Prokeš, D. Skácelová, E. M. Peña-Méndez, J. Havel. Laser ablation synthesis of new gold tellurides using tellurium and nanogold as precursors. Laser desorption ionisation time-of-flight mass spectrometry. Rapid Commun. Mass Spectrom. 27,1600 (2013).

[6] N. R. Panyala, E. M. Peña-Méndez, J. Havel. Laser ablation synthesis of new gold phosphides using red phosphorus and nanogold as precursors. Laser desorption ionisation time-of-flight mass spectrometry. Rapid Commun. Mass Spectrom. 26, 1100 ( 2012).

[7] L. Prokeš, E. M. Peña-Méndez, E. J. Conde, M. Alberti, J. Havel, Laser ablation synthesis of new gold arsenides using nano-gold and arsenic as precursors. Laser desorption ionisation time-of-flight mass spectrometry and spectrophotometry, Rapid Commun. Mass Spectrom. 28 (6), 577-586 (2014).

[8] J. Havel, E. M. Peña-Méndez, F. Amato, N. R. Panyala, V. Buršíková, Laser ablation synthesis of new gold carbides. From gold-diamond nano-composite as a precursor to gold-doped

diamonds. Time-of-flight mass spectrometric study. Rapid Commun. Mass Spectrom. 28, 297 (2014).

[9] R. M. Mawale, F. Amato, M. Alberti, J. Havel. Generation of AupAgqTer clusters via laser ablation synthesis using Au-Ag-Te nano-composite as precursor. Quadrupole ion trap time-of-flight mass. Rapid Commun. Mass Spectrom 28, 1601 (2014).

Figure: Scheme of LDI TOF MS analysis of solid sample (left) and an example of TOF mass spectrum concerning Ga-Ge-Sb-S glass doped with erbium [4].

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1Nanobiotechnology for Diagnostic group (Nb4D). IQAC- CSIC, Spain

www.iqac.csic.es/nb4d 2CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN)

Jordi Girona 18–26, 08034 Barcelona, Spain.

Biosensors play an important role in the biomedical research, drug and therapy discovery and health care. Two of the main application fields are in the personalized therapeutics for adjust the therapeutic agents dose (i.e. the glucose sensor for insulin dependent diabetes) and in point of care testing (POCT) devices. The main objective in this work is the development of an electrochemical immunosensor used to detect cardiac troponin I (cTnI) which is considered the golden biomarker for the diagnosis of acute myocardial infarction (AMI). cTnI play an important role in the accurate diagnosis of AMI and more importantly, is a powerful tool for assessing risk and give good therapies improving clinical outcomes (Aldous 2013). cTnI is released to the bloodstream after AMI episode and elevated levels of this biomarker mean severe and probably irreversible damage of the myocardium. Therefore an early detection of cTnI levels in blood could allow to us to make an accurate diagnostic of the disease and to predict patient outcome (Jillian R. Tate 2008). Aditionally, cTnI is a good marker for risk stratification (MEMBERS, Morrow et al. 2007). Values of cTnI exceeding the 99th percentile of a reference control group are closely related with AMI episodes. These values are around 0.02 – 0.08 ng/mL (Eggers, Jaffe et al. 2009). We present in this work a columbimetric immunoassay for the detection of cTnI. Different polyclonal antibodies were produced against cTnI detection, ones by immunization of the whole proteins and others by immunization of selected sequences of different epitopes of cTnI. It was done taken into account the different areas of the

protein avoiding susceptible areas to be eclipsed by preventing its immunodetection. All of these antibodies were tested by ELISA assay, and after their evaluation, they were used to develop a columbimetric immunodevice. The selected antibodies were As220 used as a capture antibody and produced against the whole cTnI, and As260 used as detection antibody produced against a selected cTnI epitope. The immunosensor presented uses a screen-printed electrodes (SPE), biofunctionalized magnetic μ-particles with a capturing antibody Ab220 and electrochemical nanoprobes prepared by labeling the detection antibody Ab260 with CdS nanoparticles (CdSNP) (Valera, Muriano et al. 2013). The different stages of the assay are showed in Figure 1. The immunoreactions took place in one step by the incubation of the sample (containing cTnI) Ab260 labeled with CdSNP and Ab220 immobilized to the magnetic beads. After this incubation step, the complex was washed 3 times and resuspended in the appropriate volume of measuring buffer and deposited on the working electrode. The signal were provide taking advantatge of the characteristic redox potential of the Cd, applying a stripping voltammetry, The intensity of this peak is directly related with cTnI concentration, showing a good dose-dependence. Due to the amplification effect on the amperometric/coulombimetric signal produced by the CdSNP, a high detectability can be reached such as a LOD of 0,004 ng/mL in buffer. In order to study the reproducibility of the assay, it has been repeated three different days, showing in all the cases good results (Figure 2).

Alejandro Hernández-Albors1,2, Enrique Valera2,1, Glòria Colom1,2, J.-Pablo Salvador2,1 and M.-Pilar Marco1,2 [email protected]


References

[1] Eggers, K. M., A. S. Jaffe, et al. (2009). "Value of Cardiac Troponin I Cutoff Concentrations below the 99th Percentile for Clinical Decision-Making." Clinical Chemistry 55(1): 85- 92.

[2] Jillian R. Tate, M. P. (2008). "Measurement of cardiac troponins revisited." Biochimica clínica 32(6).

[3] MEMBERS, N. W. G., D. A. Morrow, et al. (2007). "National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines: Clinical Characteristics and Utilization of Biochemical Markers in Acute Coronary Syndromes." Circulation 115(13): e356-e375.

[4] Valera, E., A. Muriano, et al. (2013). "Development of a Coulombimetric immunosensor based on specific antibodies labeled with CdS nanoparticles for sulfonamide antibiotic residues analysis and its application to honey samples." Biosensors and Bioelectronics 43(0): 211-217.

Figure 2. Cardiac Troponin calibration curve developed by columbimetric immunosensor.

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Figure 1. Different Steps of the columbimetric immunosensor developed.

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1CIC nanoGUNE, 20018 Donostia-San Sebastián, Spain

2IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain.

3I.N.T.I.–CONICET, Av. Gral. Paz 5445, Ed. 42, B1650JKA, San Martín, Bs As, Argentina

4Graphenea SA, 20018 Donostia-San Sebastián, Spain

5ICFO-Institut de Ciéncies Fotoniques, Mediterranean Technology Park,

08860 Casteldefells, Barcelona, Spain. 6CIC nanoGUNE and UPV/EHU, 20018 Donostia-San Sebastián, Spain

A promising solution for active control of light on the nanometer scale are plasmons in graphene, which offer ultra-short wavelengths, long lifetimes, strong field confinement, and tuning possibilities by electrical gating [1,2]. The huge momentum mismatch between graphene plasmons and photons, however, presents a major technological challenge. Here, we present and discuss the coupling of incoming light into propagating graphene plasmons based on resonant optical antennas, constituting an essential step for the development of graphene plasmonic circuits [3]. The antennas were fabricated by electron beam lithography on CVD-grown monolayer graphene. By interferometric near-field microscopy we map the propagating plasmons launched by the antennas (Fig. 1). Focusing and refraction of antenna-launched graphene plasmons will be demonstrated and discussed.

References

[1] J. Chen, et al., Nature 487, 77 (2012) [2] [2] Z. Fei, et al., Nature 487, 82 (2012) [3] [3] P. Alonso-González et al., Science 344, 1369

(2014).

Figure 1. Launching graphene plasmons with a metal antenna. Left: Schematics of the s-SNOM experiment. Right: Topography of a gold nanoantenna on graphene (top) and near-field image showing the fields of the antenna and the graphene plasmons around the antenna (bottom). The near-field image was taken at an illumination wavelength of 11.06 μm and shows the real part of the imaged field. The distance between fringes of the same color reveals the graphene plasmon wavelength.

Reiner Hillenbrand2,6, P. Alonso-González1, A.Y. Nikitin1,2, F. Golmar1,3, A. Centeno4, A. Pesquera4, S. Vélez1, J. Chen1, F. Koppens5, A. Zurutuza4, F. Casanova1,2 and L.E. Hueso1,2 [email protected]

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1IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany

2Faculty of Engineering, Al-Quds University, East Jerusalem, Palestine

3Institute of Physics, TU Chemnitz, Germany

Single wall carbon nanotubes (SWCNTs) got attracted widespread attention,[1] due to their electrical and physical exceptional properties.[2] Closely packed arrays of parallel SWCNT have been attractive candidates for the future nanoelectronics,[3,4] because of their exceptional properties, including high mobility and the relatively large currents that they can sustain.[5,6] The next industrial generation of CNT-based nanoelectronics is hampered by several major problems, despite the outstanding performance of individual CNT-based devices.[7] Such challenges include the lack of reliable methods to control the alignment and position of the as-grown nanotubes and simultaneous growth of metallic and semiconducting nanotubes.[8] Controlling spatial position and structural selectivity during the synthesis would thus be beneficial for many of the potential applications of SWNTs.[6] Significant improvements have been shown regarding the development of reliable routes for growing in-place well aligned SWCNT on different types of substrates using chemical vapor deposition (CVD) process.[6,7] CVD is proven to be the most versatile and promising technique due to upscale possibility and technology compatibility.[3,9] In parallel, researchers have shown successful separation of metallic and semiconducting CNTs by applying solvents-based routes.[10] However, such routes have many drawbacks, as the attractive CNT properties are altered due to the necessary hard treatment steps.[6] Such process essentially introduces defects and shortens the resultant nanotubes. Alternatively, CVD is thought to be a significant approach for the in-place growth of type-selective SWCNT.[11] On the other hand, the coexistence of metallic and semiconducting nanotubes in such samples is still a problem and should be overcome before real industrial integration of CNT in device fabrication. It was shown that horizontally aligned semiconducting-rich SWCNT can be grown on single crystal ST-cut quartz substrates by using optimized CVD process.[7] The actual mechanisms behind the sc-enrichment is still an open question, i.e is it a CVD process effect or due to the forces taking place between the grown CNTs and the

surface atoms of the support substrate. In the case of CVD process effect, that is extremely positive and opens a window where the route can be further developed toward growth of pure sc-SWCNT or even single chirality SWCNT. If it is a CNT-substrate attraction effect, a detailed and systematic study is required in order to understand the effect of such attraction on the electrical properties of the grown nanotubes. More precisely, does the CNT-substrate attraction affect the performance of electronic devices later fabricated with such CNT? In this study, we aimed for deeper understanding of the actual mechanisms behind the sc-enrichment CNT grown by CVD. We performed a systematic study, in which we grow SWCNT by CVD on different support substrates under a variety of process conditions. The grown CNT are either lattice-oriented in the case of ST-cut quartz substrates and sapphire substrates or randomly oriented when silicon substrates were used. The variety of the investigated CVD parameters, i.e. catalyst materials and C precursor, allows for thorough understanding resulting in realistic conclusions. Representative SEM micrographs of the as-grown SWCNT using binary catalyst system (Fe:Co = 2:1 atomic ratio) on different substrates, i.e. ST-cut quartz and sapphire, are shown in figure 1. Both substrates allow growth of horizontally aligned nanotubes, despite that on sapphire the alignment is not perfect as on ST-quartz.[6] The as-grown CNT were transferred onto silicon target substrates using pre-optimized protocol for further characterization.[9] It was advantageous to transfer the grown nanotubes onto substrate, so that the Raman signal form them does not overlap with the that from support substrate as in the case of quartz and sapphire. Three factors were investigated here, the catalyst nanoparticles (binary system), the C precursor and the support substrate. Ethanol was used as the main C precursor, while methanol was introduced as OH radicals supplier. It is believed that these radicals can effectively etched the m-CNT due to their smaller ionization potential compared to s-CNT,[12] in addition to prevent formation of amorphous carbon on the

Imad Ibrahim1,2 J. Kalbáčová3, V. Meier1, R. D. Rodriguez3, D. Grimm1, J. Eckert1 and Mark H. Rümmeli1 [email protected]


nanotubes as well on the substrate.[7] Typical Raman spectra of the transferred CNT onto Si substrates, originally grown on ST-cut quartz with different C precursor combination, i.e. Ar bubbles through ethanol and Ar bubbles through methanol, are shown in figure 2.a. It is obvious that the RBM peaks become sharper and stronger as methanol percentage is increased, indicating a positive effect of methanol toward enrichment of s-CNT. In addition, the number of the RMB peaks becomes smaller. This indicates growth of CNT with narrower diameter distribution.[13] The analysis of the Raman spectra collected for CNT grown on different substrates (figure 2.b), with optimized ethanol:methanol ratio for enriched s-CNT samples, reveals that rich s-CNT samples were obtained when using crystalline substrates, i.e. quartz and sapphire, while mixture of m- and s-CNT, with improved ratio, obtained on the silicon substrates. However, the RBM peaks suggest that the CNT grown on quartz are with narrower diameter distribution than those grown on sapphire. These observations were confirmed when characterizing the grown CNTs under different growth conditions with the 633 nm excitation line. In summary, it is more likely that the growth selectivity is attributed to the effect of process parameters, and secondly to the attraction forces between the grown CNT and the support substrates. Systematic identification of m- and s-CNT in scanning electron microscopy [14] along with the electrical performance of thin film transistors fabricated with the as-grown nanotubes under different conditions allow for better understanding and realistic conclusions.. References [1] Q. Wen, W. Qian, J. Nie, A. Cao, G. Ning et al, Adv.

Mater. 22 (2010) 1867. [2] S. J. Tans, A.R.M.; Verschueren, C. Dekker, Nature

393 (1998) 49. [3] S. J. Kang, C. Kocabas, Ozel, M. Shim, N. Pimparkar

et al, Nature nanotech. 2 (2007) 230. [4] Z. Chen, J. Appenzeller, Y.M. Lin, J. Sippel-Oakley, A.

G. Rinzler et al, Science 311 (2006) 1735. [5] N. Rouhi, D. Jain, K. Zand, P. J. Burke, Adv. Mater. 23

(2011) 94. [6] I. Ibrahim, A. Bachmatiuk, J. H. Warner, B. Büchner,

G. Cuniberti et al, Small 8 (2012) 1973. [7] L. Ding, A. Tselev, J. Wang,D. Yuan, H. Chu et al,

Nano Lett. 9 (2009) 800. [8] W. Kim , H.C. Choi , M. Shim ,Y. Li , D. Wang et al,

Nano Lett. 2 (2002) 703. [9] I. Ibrahim, A. Bachmatiuk, F. Börrnert, J. Blüher, S.

Zhang et al, Carbon 49 (2011) 5029. [10] R. Krupke, F. Hennrich, H. v. Löhneysen, M.M.

Kappes, Science 301 (2003) 344.

[11] X.L. Li, L. Zhang, X.R. Wang, I. Shimoyama, X.M. Sun et al, J. Am. Chem. Soc 129 (2007) 4890.

[12] J. Lu, S. Nagase, X.W. Zhang, D. Wang, M. Ni et al, J. Am. Chem. Soc. 128 (2006) 5114.

[13] Y. Che, C. Wang, J. Liu, B. Liu, X. Lin et al, ACS Nano 6 (2012) 7454.

[14] J. Li , Y. He , Y. Han , K. Liu , J. Wang , Qunqing Li et al, Nano Lett. 12 (2012) 4095.

Figure 1. Growth of SWCNT: Representative SEM images of as-grown CNT on a. ST-cut quartz and b. sapphire.

Figure 2. Effect of process parameters: Raman spectra for the a. CNT grown on ST-cut quartz with different C precursor combination and later transferred onto Si substrate, and b. CNT grown on different substrates with Eth:Meth = 0.25:0.25 LPM. [515 nm excitation line was used. All spectra were normalized to the G mode of the same signal]

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Institute of Physics, Nicolaus Copernicus University, Grudziadzka 5, Toruń, Poland Donostia International Physics Center, San Sebastian, Spain Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, C/ Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain Departamento de Física Fundamental, Universidad Nacional de Educacion a Distancia, Madrid, Spain

Graphene presents frequently grain boundaries and defect lines, which occur spontaneously in the process of growth or can be created on demand [1,2]. Grain boundaries have been measured to affect both the electronic transport and the magnetic properties of graphene because they present localized states with energies at or close to the Fermi level [3-6]. Such states allow also for the decoration of defect lines with adsorbates, opening a route for nanosensor applications. As the electronic properties of graphene are modified by the localized states at the grain boundaries, the final control of graphene-based devices requires the tailoring and engineering of such defect lines. However, the relation between the geometry of grain boundaries and the induced electronic localized states has not been so far understood. Defect lines in graphene can be seen as the outcome of matching of two graphene sheets with different edges, which produces localized states. Recently, general rules to predict the existence of edge-localized states and flat bands at the Fermi level in graphene nanoribbons with arbitrary shape of the edges have been given [7]. The localization at defect lines built of octagonal rings has also been understood as a consequence of the zigzag nature of the graphene edges forming the defect lines [8]. Here we bring into contact these ideas about localized states in graphene edges to give a more comprehensive explanation of states appearing in extended defect lines in graphene. We classify the energy spectra of grain boundaries into three types only, relating them directly to the basic classes of spectra of graphene edges [7]. These classes are presented in Fig. 1. We have found a simple formula, based on the topology of grains, which allows to obtain the number of interface bands

with energies in the gap and close to the Fermi level. When two graphene edges are connected forming a grain boundary, the pairs of states localized at different edges strongly hybridize and split, usually reaching the energy band continua. The remaining unpaired states (which originate from one edge only) constitute the grain boundary localized bands with energies close to the Fermi level. An example for the grain boundary formed by joining a pure zigzag edge and a chiral edge defined by the edge-translation vector (4,1), is shown in Fig. 2. Our method to find localized bands around the Fermi energy provides a new understanding on states localized at grain boundaries, showing that they are derived from the edge states of graphene, and allowing for the prediction of their electronic characteristics without performing numerical calculations. Such knowledge is crucial for defect engineering towards practical electronic and optoelectronic applications based on graphene and carbon nanotubes, which strongly depend on the spectrum near the Fermi energy.

References

[1] A. N. Obraztsov, Nature Nanotechnology 4 (2009) 212.

[2] X. Li, W. Cai, J. An, S. Kim, J. Nah, D. Yang, R. Piner, A. Velamakanni, I. Jung, E. Tutuc, S. K. Banerjee, L. Colombo, and R. S. Ruoff, Science 324 (2009) 1312.

[3] K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J.-H. Ahn, P. Kim, J.-Y. Choi, B. H. Hong, Nature 457 (2009) 706.

[4] K. W. Clark, X.-G. Zhang, I. V. Vlassiouk, G. He, R. M. Feenstra, A.-P. Li, ACS Nano 7 (2013) 7956

W. Jaskólski, A. Ayuela, L. Chico and H. Santos [email protected]


[5] J.C. Koepke, J.D. Wood, D. Estrada, Z.Y.Ong, K.T. He, E. Pop, J.W. Lyding, ACS Nano 7 (2013) 75.

[6] P. Y. Huang, C. S. Ruiz-Vargas, A. M. van der Zande, W. S. Whitney, M. P. Levendorf, J. W. Kevek, S. Garg, J. S. Alden, C. J. Hustedt, Y. Zhu, J. Park, P. L. McEuen, D. A. Muller, Nature 469 (2011) 389.

[7] W. Jaskolski, A.Ayuela, M. Pelc, H. Santos, and L. Chico, Phys. Rev. B. 83 (2011) 235424.

[8] M. Pelc, L. Chico, A. Ayuela, and W. Jaskolski, Phys. Rev. B. 87 (2013) 165427

Figure 1. Three possible band structures E(k) for periodic grain boundaries in graphene. k is along the direction corresponding to the grain boundary. Gray areas schematically represent the band continua. Solid horizontal lines represent gap bands with energies close to the Fermi level and localized at grain boundary. The number of such bands is uniquely determined by the topology of the grain boundary. In cases (a) and (b) the numbers N and N' of the bands at the left- and right-hand side of the Dirac cone may be different (can be even equal to zero).

Figure 2. (a) Geometry of the grain boundary formed by joining pure zigzag edge (upper one) with the chiral edge defined by translation vector (4,1). Periodicity of the zigzag edge is adjusted to the chiral edge (4,1) and equals (5,0). (b) and (c): Schematic energy spectra of the chiral (4,1) and zigzag (5,0) edges, respectively. (d) Schematic spectrum of the (5,0)/(4,1) boundary, in good agreement with (e) the calculated density of states (DOS) at the (5,0)/(4,1) boundary. Darker color indicates a larger DOS value. One zero-energy band localized at the zigzag (5,0) edge hybridizes with the band localized at the chiral (4,1) edge; they strongly split and merge the band continua. The remaining band, which extends from k=0 to the Dirac cone, originates from the zigzag edge and constitute the final band localized at the grain boundary.

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1Departament d’Enginyeria Electrònica, Escola d’Enginyeria, Universitat Autònoma de

Barcelona, Bellaterra, Spain 2ICN2, Institut Català de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra

(Barcelona), Spain

While graphene has emerged as a promising material for future electronic devices thanks to its unique electronic properties, the metal-graphene contact resistance (Rc) remains a limiting factor for graphene-based electronic devices. In particular, for high frequency electronics is an issue, very much influencing figures of merit like the maximum frequency of oscillation, the cutoff frequency, or the intrinsic gain. That is why there is a need to understand the intrinsic and extrinsic factors determining the contact resistance, which displays a strong variation depending on the metal contact and fabrication procedure details. To gain understanding of the intrinsic factors, a comprehensive physics based model of the contact resistance is worthy. One relevant model was already proposed by Xia et al. [1] to describe the transport in metal-graphene junctions as a sequential tunneling process from the metal to graphene underneath followed by injection to the graphene channel. The first process is responsible for the resistance between the metal and the graphene underneath (Rmg) and the second process includes the resistance due to the potential step across the junction formed between the graphene under the metal and the graphene channel (Rgg). However, there is an important ingredient determining Rc namely, the transmission from a 3D system (metal) to a 2D system (graphene), that was not properly considered in a physics basis. So, in order to improve the state-of-the-art and current understanding, we have taken this issue of the carrier transmission from 3D to 2D systems into consideration [2]. Specifically, we have developed a physics-based model where the calculation of Rmg and Rgg are based on the Bardeen Transfer Hamiltonian (BTH) method and the Landauer approach, respectively. The BTH method allows us

to get information about the matrix elements for the transition between 3D-metal and 2D graphene states and combined with Fermi's golden rule, yields a compact expression for the specific contact resistivity. On the other hand, the Landauer approach allows to get the conductance of carriers across the potential step between the graphene under the metal and the graphene in the channel, where the angular dependence transmission of fermions have been taken into account. As an illustrative example of the predictive capability of our model we have compared our results with available experimental data from Ref. 1 for Pd-graphene contacts (see Fig. 1). The chemical vapor deposition (CVD) technique for growing wafer-scale graphene on metallic substrates produces a polycrystalline pattern. This is because the growth of graphene is simultaneously initiated at different nucleation sites, leading to samples with randomly distributed grains of varying lattice orientations. It has recently been predicted that the electronic properties of polycrystalline graphene differ from those of pristine graphene (PG), where the mobility scales linearly with the average grain size [3]. Based on these results, we report on how the electronic properties of polycrystalline graphene (Poly-G) impact the behavior of graphene-based devices. For such a purpose, we have developed a drift-diffusion transport model for the graphene field-effect transistor (GFET), based on a detailed description of electronic transport in polycrystalline graphene [4]. This model allows us to determine how a graphene sample’s polycrystallinity alters the electronic transport in GFETs, enabling the prediction and optimization of various figures of merit for these devices. Specifically, we

David Jiménez1, Ferney A. Chaves1, Aron W. Cummings2, and Stephan Roche2 [email protected]


concentrate our study on the effect that Poly-G has on the gate electrostatics and I-V characteristics of GFETs. We find that the source-drain current and the transconductance are proportional to the average grain size, indicating that these quantities are hampered by the presence of grain boundaries (GBs) in the Poly-G. Besides, our simulations also show that current saturation is improved by the presence of GBs, and the intrinsic gain is insensitive to the grain size. We have found that the presence of GBs produces a severe degradation of both the maximum frequency and the cutoff frequency, while the intrinsic gain remains insensitive to the presence of GBs (Fig. 2). These results indicate that GBs play a complex role in the behavior of graphene-based electronics, and their importance depends on the application of the device. Overall, polycrystallinity is predicted to be an undesirable trait in GFETs targeting analog or RF applications. We acknowledge support from SAMSUNG within the Global Innovation Program. The research leading to these results has received funding from Ministerio of Economía y Competitividad of Spain under the project TEC2012-31330 and MAT2012-33911, and from the European Union Seventh Framework Programme under grant agreement n°604391 Graphene Flagship.

References

[1] F. Xia et al., Nature Nanotechnology 6, 79 (2011)

[2] F. Chaves, D. Jiménez, A. Cummings, S. Roche, Journal of Applied Physics 115, 164513 (2014),

[3] D. V. Tuan, J. Kotakoski, T. Louvet, F. Ortmann, J. C Meyer, S. Roche, Nano Lett. 13, 1730-1735 (2013).

[4] D. Jiménez, A. W. Cummings, F. Chaves, D. Van Tuan, J. Kotakoski, S. Roche, Applied Physics Letters 104, 043509 (2014).

Figure 1. Experimental versus simulation of Pd-graphene junction contact resistance as a function of the gate bias overdrive.

Figure 2. Left: Intrinsic gain as a function of the drain voltage. Right: Intrinsic maximum and cutoff frequency for a prototypical transistor with a channel length of 100 nm.

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1Department of Electronics, Bioelectronics and Nanobioengineering Research Group

(SIC-BIO), University of Barcelona, Martí i Franquès 1, 08028, Barcelona, Spain 2 Department of Public Economy, Political Economy and Spanish Economy, University of

Barcelona, Av. Diagonal 690-696, 08034 Barcelona, Spain 3 CREB-Biomedical Engineering Research Centre, Technical University of Catalonia,

Pau Gargallo 5, 08028 Barcelona, Spain 4 IBEC-Institute for Bioengineering of Catalonia, Nanobioengineering Research Group,

Baldiri Reixac 10-12, 08028 Barcelona, Spain 5 CIBER-BBN-Biomedical Research Networking Center in Bioengineering, Biomaterials

and Nanomedicine, María de Luna 11, Edificio CEEI, 50018 Zaragoza, Spain

This paper describes an innovative nano-enabled implantable device for in-vivo biomarkers monitoring that could be suitable for customized theranostics applications. Findings suggest that cross-cutting Key Enabling Technologies (KETs), i.e. nanotechnology, biotechnology, micro & nanoelectronics and advanced materials, could boost the development of new nano-enabled medical devices, using biocompatible materials, and embedding reliable and targeted biosensors. A key issue introduced by the authors is that the general architecture of the medical device could be programmable in the direction of personalized medical applications. The current interaction between medicine and technology permits the development of new diagnostic devices to detect or monitor pathogens, ions, diseases, etc. Doubtless, the integration of rapid advances in areas such as microelectronics, microfluidics, microsensors and biocompatible materials entails the availability of implantable biodevices for continuous monitoring or event detectors that carry out faster and cheaper clinical tasks than when these are done by standard methods. Implantable devices have already been used in millions of patients [1]. Benefits of these approaches include improved care and quality of life for millions of patients [2]. Implantable sensor networks can facilitate an early detection of emergency conditions and diseases in patients at risk, [3] comprising physical, physiological, psychological, cognitive, and behavioral processes,

by reaching inaccessible environments in a reduced response time [4]. It is in this context that we present an integrated front-end architecture for in-vivo customized detection. A new and challenging scenario defined as the pervasive system is focused on the development of systems capable of monitoring human bodily functions and to transmit the resultant data for a clinical patient’s monitoring [5]. Thanks to this approach, it could be possible to monitor patients anywhere and at all times with important impact on their quality of healthcare preventing the worst scenarios for the patients as well as improving the wellbeing and continuing activity of the whole population. The possibility of controlling how a therapy is working, detecting symptoms, and knowing how the disease is progressing will improve the personalized medical care known as theranostics. Patients at risk because of their genetic background, chronically ill or elderly people will be monitored outside of and beyond visits to the hospital or at the surgery. Here, the significant advantage is to monitor patients in their routine daily activities, as traditional clinical monitoring would be replaced by continuous and remote monitoring [6], which could have a great impact on patients’ quality of life and could reduce the cost of the overall healthcare system [7]. Amongst all the medical applications and diseases, findings suggest that chronic illness deserves special attention [8], particularly in the case of cardiovascular illness [9].

Esteve Juanola-Feliu1 P. Ll. Miribel-Català1, C. Páez Avilés1, J. Colomer-Farrarons1, M. González-Piñero2,3 and J. Samitier1,4,5 [email protected]


Theranostics covers a wide range of applications as health interventions with drugs (pharmacogenomics), nutrition (nutrigenomics) and vaccines (vaccinomics), as well as diagnostics for human diseases [10]. Implantable medical devices are widely used for therapeutic [4] or life-saving purposes such as cardiac arrhythmia, diabetes, and Parkinson’s disease [11]. Applications include drug delivery systems, pacemakers, implantable cardiac defibrillators (ICDs) and Neurostimulators [1]. Some real-time monitoring applications include physiological parameters like blood pressure, glucose levels and collecting data for further analysis [4]. These devices often contain electronic components that perform increasingly sophisticated sensing, computation, and actuation, in many cases without any patient interaction [1] as in the applications mentioned above, performing complex analyses with sophisticated decision-making capabilities. They are capable of storing detailed personal medical information, and communicate automatically, remotely, and wirelessly [2]. Implanted nano-enabled biosensors form a wireless network that can be used for data aggregation and data dissemination applications [4]. The system introduced in this paper is conceived to be implanted under the human skin. The powering and communication between this device and an external primary transmitter are based on an inductive link [12]. The architecture presented is designed with two different approaches: defining a true/false alarm system based on either amperometrics or impedance into a grid of nano-biosensors that could permit the monitoring of several diseases by in-vivo analysis of the corresponding biomarkers.

References

[1] Burleson, W.; Clark, S. S.; Ransford, B.; Fu, K. Design challenges for secure implantable medical devices. Proc. 49th Annu. Des. Autom. Conf. - DAC ’12 2012, 12.

[2] Maisel, W. H.; Kohno, T. Improving the security and privacy of implantable medical devices. N. Engl. J. Med. 2010, 362, 1164–6.

[3] Darwish, A.; Hassanien, A. Wearable and implantable wireless sensor network solutions for healthcare monitoring. Sensors 2011.

[4] Cherukuri, S.; Venkatasubramanian, K. K.; Gupta, S. K. S. Biosec: a biometric based approach for securing communication in wireless networks of biosensors implanted in the human body. 2003 Int. Conf. Parallel Process. Work. 2003. Proceedings. 2003, 432–439.

[5] Shen, X.; Misic, J.; Kato, N.; Langenorfer, P.; Lin, X. Emerging technologies and applications of wireless communication in healthcare. J. Commun. Networks 2011, 13, 81–85.

[6] Garcia-Morchon, O.; Falck, T.; Heer, T.; Wehrle, K. Security for Pervasive Medical Sensor Networks. In Proceedings of the 6th Annual International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services; IEEE, 2009; pp. 1–10.

[7] Zweifel, P.; Felder, S.; Meiers, M. Ageing of population and health care expenditure: a red herring? Health Econ. 1999, 8, 485–96.

[8] Koutkias, V. G.; Chouvarda, I.; Triantafyllidis, A.; Malousi, A.; Giaglis, G. D.; Maglaveras, N. A personalized framework for medication treatment management in chronic care. IEEE Trans. Inf. Technol. Biomed. 2010, 14, 464–72.

[9] Pang, T. Theranostics, the 21st century bioeconomy and “one health ”2012, 807–809.

[10] Zhou, H.; Hou, K. Pervasive Cardiac Monitoring System for Remote Continuous Heart Care. In 2010 4th International Conference on Bioinformatics and Biomedical Engineering; IEEE, 2010; pp. 1–4.

[11] Halperin, D.; Heydt-benjamin, T. S.; Maisel, W. H.; Deaconess, B. I. Security and Privacy for Implantable Medical Devices. 2008, 30–39.

[12] Juanola-Feliu, E.; Colomer-Farrarons, J.; Miribel-Català, P. L.; González-Piñero, M.; Samitier, J. Nano-Enabled Implantable Device for In Vivo Glucose Monitoring. In Implantable Bioelectronics; Katz, E., Ed.; Wiley-VCH, 2014; p. 450.

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1Keysight Technologies, Gruberstrasse 40, Linz, Austria

2Keysight Technologies, 5301 Stevens Creek Blvd, Santa Clara, USA

3University of Ulm, Institute for Analytical Chemistry, Albert-Einstein-Allee 11, Ulm,

Germany

Laterally resolved (electro) chemical information on a sample can be obtained with scanning electrochemical microscopy (SECM), where a biased ultra-microelectrode is scanned at a defined distance across the sample surface. However, conventional SECM suffers the lack of sufficient spatial resolution and the convolution of topography and electrochemical response due to the current-dependent positioning of the microelectrode. Within the last decade several approaches have been reported, for directly integrating a micro- or nanoelectrode into an AFM probe. In order to maintain the functionality of both techniques, the integrated electrode is recessed from the end of the AFM tip. Consequently, the electrode is located at a defined distance to the sample surface, which is now defined by the length of the actual AFM tip. Thus, by applying a potential to this AFM-SECM probe and recording the Faradaic current related to electroactive surface processes, laterally resolved (electro)chemical information can be directly correlated to the topographical information obtained by the AFM measurement. So far, combining AFM with SECM required customized solutions, as no commercial SECM module for AFM systems was available and therefore the technology could only be used by a limited number of researchers. Recently we have succeeded in bringing an SECM module onto a commercial AFM platform, providing a dedicated mount with integrated preamplifier for AFM-SECM probes and a bi-potentiostat, which allows to control the potential of the sample and the AFM tip-integrated electrode. This mechanism not only greatly minimizes the effort required for experimental

setup, but also enables the capability of multifunctional imaging and surface modification with combined AFM-SECM modes. The advantage of the combined technique is that measurements are not limited to amperometry but can be extended to a multitude of electroanalytical techniques during AFM imaging. Several applications of this new SECM approach will be shown, starting from test structures up to redox-mediated membrane transport in cell membranes.

References

[1] C. Kranz, Analyst, 139 (2014) 336-352. [2] J. V. Macpherson, P. R. Unwin, Anal Chem, 72

(2000), 276-285. [3] C. Kranz, G. Friedbacher, B. Mizaikoff, A.

Lugstein, J. Smoliner, E. Bertagnolli, Anal Chem, 73 (2001), 2491-2500.

[4] A. Kueng, C. Kranz, A. Lugstein, E. Bertagnolli, B. Mizaikoff, Angew. Chem. Int. Ed, 44 (2005), 3419-3422.

[5] C. Kranz, J. Wiedemair, Anal Bioanal Chem, 390 (2008), 239-243.

[6] S. Wu, Agilent Technologies Datasheet (2014), 5991-4525EN

Gerald Kada1, Shijie Wu2 and Christine Kranz3 [email protected]


Figure 1. (Left) Electron microscopy image of an AFM tip with integrated nano-electrode for SECM. (Right) Applications of SECM using derivatized electrodes.

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1LPS, Univ. Paris-Sud, CNRS, UMR 8502, F-91405 Orsay Cedex, France

2CSNSM, Univ. Paris-Sud, IN2P3, UMR?, F-91405 Orsay Cedex, France

3 Faculty of Chemistry, Moscow State University, leninskie Gory, 1-str.3, Moscow,

119991, Russia 4Department of materials science, Moscow State University, Leninskie Gory,

Moscow, 119991, Russia 5Institute of Microelectronics Technology and High Purity Materials, RAS, ac. Ossipyan, 6

Chernogolovka, Moscow District, 142432, Russia

In the superconducting proximity effect, singlet pair correlations can penetrate quite far (on the micron scale) into a non superconducting (normal) conductor. This penetration, that can lead to supercurrents through normal conductors several micrometers long connected to two superconductors, results from quantum interference between all conduction channels in the sample. In a microscopic picture, the supercurrent is carried by Andreev states, combinations of time reversed electron and hole wavefunctions confined to the normal conductor. It is thus natural to consider that this interference will be destroyed not only by inelastic scattering, but also by time reversal symmetry breaking. Indeed, a magnetic field is known to suppress the supercurrent via both orbital (Aharonov Bohm phase accumulation) and spin (Zeeman dephasing) effects. Nevertheless, supercurrents have been induced through ferromagnets. The oscillatory sign and decaying intensity of the supercurrent with increasing ferromagnet thickness is an illustration of the dephasing role played by the exchange field. On the other hand, the time reversal invariant spin orbit interactions, by imposing strong correlations between spatial and spin components of the induced Andreev pairs, offer new possibilities such as coupling between singlet and triplet pairing [1, 2], arbitrary Josephson phase shifts in an exchange or a Zeeman field (ϕ junction behavior) [3] and the possible formation of Majorana fermions at the interface between semiconducting nanowires and superconducting electrodes [4].

In this report, we probe the superconducting proximity effect in bismuth crystalline nanowires, a system with extremely high Rashba spin orbit coupling, connected to superconducting electrodes with standard s-wave pairing and a very high critical field. The complex interference pattern we measure (Fig.1 and Fig.2), up to magnetic fields such that the Zeeman energy becomes of the order of the spin-orbit and Fermi energies, uniquely reveals the role played by both spin and orbital degrees of freedom.

References

[1] Lev P. Gor’kov and Emmanuel I. Rashba, Phys. Rev. Lett. 87 (2001) 037004.

[2] F. S. Bergeret, A. F. Volkov, K. B. Efetov Rev. Mod.Phys. 77 (2005) 1321.

[3] A.Buzdin Phys. Rev. Lett. 101 (2008) 107005. [4] R. M. Lutchyn, J. D. Sau, and S. D. Sarma, Phys.

Rev. Lett. 105 (2010) 077001. V. Mourik et al. Science 336 (2012) 1003

A. Kasumov1, C. Li1, A. Murani1, S. Sengupta2, F. Fortuna2, K. Napolskii3,4, D. Koshkodaev 4, G. Tsirlina3, Y. Kasumov5, I. Khodos5, R. Deblock1, M. Ferrier1, S. Guéron1 and H. Bouchiat1

[email protected]


Figure 1. Field dependence of the supercurrent of Bi1 (top curve) and Bi3 (bottom curves), in a perpendicular magnetic field. Fast, squid-like oscillations are visible on scales of 800 and 150 G for Bi1 and Bi3 respectively, up to unusually high fields (up to at least 6 T for Bi1, and to 10T for Bi3). An additional periodic modulation with a 2300 G period is seen for Bi3, and an irregular modulation in the Tesla range modulates the critical current of Bi1. On Bi3 two kind of switching measurements were done with different time scales. As expected, the measurements (b) and (c), performed on a shorter time scale, yield somewhat higher switching current values than the slow measurements (d) and (e). Inset: Scanning electron micrograph of Bi1, connected by superconducting W wires.

Figure 2. (a) Left panel: Color plot of the field dependence of the differential resistance of Bi2, with some characteristic differential resistance curves (right panel). (b) and (c) Field dependence of the critical current and zero bias differential resistance extracted from the colorplot (a). Note the oscilla¬tory behaviour on the 1 Tesla field scale, and also how the maximal critical current increases with field.

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1J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague 8, Czech Republic. 2Institute of Physics, v.v.i., Academy of Sciences of the Czech Republic Na Slovance 2,

18221, Prague 8, Czech Republic 3IMEC, IMOMEC Division, University Campus Hasselt, Wetenschapspark 1, B-3590 Diepenbeek, Belgium

Nanocrystalline boron doped diamond films were grown by a microwave plasma enhanced chemical vapor deposition and surface-terminated either by hydrogen or oxygen.[1] Electrochemical impedance spectroscopy in aqueous electrolyte solution provided the flatband potentials and concentrations of acceptors, which relate to the B-concentrations obtained from the neutron depth profiling. Electrochemical cleaning of the surface from sp2 carbon impurities was demonstrated by Raman spectroscopy.[2] In-situ Raman spectroelectrochemistry shows that Raman response of sp3 carbon is intact to electrochemical charging, whereas the D, G and D’ Raman modes of the sp2 carbon impurities are not. The quality of nanocrystalline diamond electrodes can be thus analyzed in detail. Spectral sensitization of the nanodiamond surface was carried out by anchoring of dyes like 4-(bis-{4-[5-(2,2-dicyano-vinyl)-thiophene-2-yl]-phenyl}-amino)-benzoic acid (P1 from Dyenamo AB). The target device is a nanodiamond-based p-type dye-sensitized solar cell, which is an alternative of the well known n-type dye-sensitized soalr cell based on titania photoanode. Acknowledgement This work was supported by the Grant Agency of the Czech Republic (contract No. 13-31783S).

References

[1] P. Ascheulov, J. Sebera, A. Kovalenko, V. Petrak, F. Fendrych, M. Nesladek, A. Taylor, Z. Vlckova-Zivcova, O. Frank, L. Kavan, M. Dracinsky, P. Hubik, J. Vacik, I. Kraus, I. Kratochvilová, Eur. Phys. J. B, 86 (2013) 443.

[2] Z. Vlckova-Zivcova, O. Frank, V. Petrak, H. Tarabkova, J. Vacik, M. Nesladek, L. Kavan, Electrochim. Acta, 18 (2013) 518.

L. Kavan1, Z. Vlckova-Zivcova1, H. Krysova1, V. Petrak2, O. Frank1, P. Janda1, H. Tarabkova1, M. Nesladek2,3 [email protected]

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ICFO, The Institute of Photonic Sciences Mediterranean Technology Park Av. Carl Friedrich Gauss 3. 08860 Castelldefels (Barcelona), Spain

In this talk, we use 2d materials to tailor novel nano-optoelectronic capabilities, exploiting strong-light matter interactions at the nanometer scale. First, we will discuss the strong near-field interactions between graphene and nanoscale light-emitters [1,2]. Because graphene is gapless with tunable carrier density, it can effectively behave as a semiconductor, a dielectric, or a metal. We exploit this to electrically control optical emitter relaxation pathways [2]. Specifically, we control whether emitter excitations are converted into either photons, electron-hole pairs, or plasmons with confinement to the graphene sheet below 15 nm. Additionally, we electrically detect the transferred energy from the emitter into the graphene, enabling all-electrical detection of the diamond NV center spin [3]. Second, we address the highly confined optical fields (plasmons) [4,5] in heterostructures of graphene and hexagonal boron nitride [6]. We find unprecedented low plasmon damping, while the device structures enable even stronger field confinement than for earlier graphene plasmon devices. Based on these results, we address new configurations to electrically control and detect plasmons, and develop a detailed understanding of their decay mechanisms and coupling to electronic excitations. Finally, we discuss the carrier dynamics in graphene from a broader perspective, evaluating the potential for new classes of opto-electronic devices [7].

References [1] Universal distance-scaling of nonradiative energy

transfer to graphene L. Gaudreau, K. J. Tielrooij, G. E. D. K. Prawiroatmodjo, J. Osmond, F. J. García de

Abajo, F. H. L. Koppens. Nano Lett. 13, 2030-2035 (2013)

[2] Electrical control of optical emitter energy relaxation pathways enabled by graphene K.J. Tielrooij, L. Orona, A. Ferrier, M. Badioli,1, G.

Navickaite, S. Coop, S. Nanot,B. Kalinic, T. Cesca,5 L. Gaudreau, Q. Ma, A. Centeno, A. Pesquera, A. Zurutuza, H. de Riedmatten, P. Goldner, F.J. Garcia de Abajo, P. Jarillo-Herrero, and F.H.L. Koppens To be published (2014)

[3] Ultrafast electronic read-out of diamond NV centers coupled to graphene Andreas Brenneis, Louis Gaudreau, Max Seifert, Helmut Karl, Martin S. Brandt, Hans Huebl, Jose A. Garrido, Frank H.L. Koppens, Alexander W. Holleitner ArXiv1408.1864 (2014)

[4] Controlling graphene plasmons with resonant metal antennas and spatial conductivity patterns P. Alonso-González, A. Y. Nikitin, F. Golmar, A. Centeno, A. Pesquera, S. Vélez, J. Chen, G. Navickaite, F. Koppens, A. Zurutuza, F. Casanova, L. E. Hueso, R. Hillenbrand Science 344, 1369-1373 (2014)

[5] Optical nano-imaging of gate-tunable graphene plasmons J. Chen, M. Badioli, P. Alonso-González, S. Thongrattanasiri, F. Huth, J. Osmond, M. Spasenović, A. Centeno, A. Pesquera, P. Godignon, A. Zurutuza Elorza, N. Camara, F. J. García de Abajo, R. Hillenbrand, F. H. L. Koppens Nature 487, 77-81 (2012)

[6] Highly confined low-loss plasmons in graphene–boron nitride heterostructures Achim Woessner, Mark B. Lundeberg, Yuanda Gao, Alessandro Principi, Pablo Alonso-Gonz alez, Matteo Carrega, Kenji Watanabe, Takashi Taniguchi,

GiovanniVignale, Marco Polini, James Hone, Rainer Hillenbrand, and Frank H.L. Koppens To be published (2014)

[7] Photoexcitation cascade and multiple hot-carrier generation in graphene K. J. Tielrooij, J. C. W. Song, S. A. Jensen, A. Centeno, A. Pesquera, A. Zurutuza Elorza, M. Bonn, L. S. Levitov, F. H. L. Koppens Nature Phys. 9, 248-252 (2013).

Frank Koppens

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Nanomedicine Lab, Faculty of Medical & Human Sciences and National Graphene Institute University of Manchester, Manchester M13 9PT, United Kingdom

Graphene materials have entered a phase of maturity in their development that is characterized by their explorative utilization in various types of applications and fields from electronics to biomedicine. Various recent advances have been made at the proof-of-principle level with graphene-related materials in a wide range of biomedical applications [1]. Graphene materials today have mainly been explored as components of biosensors and for construction of matrices in tissue engineering, along with their antimicrobial activity and their capacity to act as drug delivery platforms [4]. This emerging landscape will be discussed in the context of three main categories of biomedical applications: a) devices; b) matices, and c) transporter systems. Each of these categories has different requirements and specifications that can be met only after careful selection of specific, well-characterised types of graphene materials [2]. The combination between graphene material type [3] with each specific application will determine the challenges and limitations to confront graphene-based constructs as they are explored further towards clinical use. Overall, this talk will attempt to offer some perspective as to which areas of biomedical applications we can expect graphene-related materials to constitute a tool that can offer improved functionality.

References

[1] Bitounis, D. et al. Advanced Materials, 2013, 25(16), 2258-2268.

[2] Kostarelos, K. and Novoselov K.S. Science, 2014, 344, 261-263.

[3] Wick, P. et al. Angew Chemie, 2014, 53, 2-7. [4] Kostarelos, K. and Novoselov K.S. Nature

Nanotechnology, 2014, 9(10), 744-745

Kostas Kostarelos

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Technological Institute for Superhard and Novel Carbon Materials, Centralnaya str. 7a, Troitsk 142190, Moscow, Russian Federation

The experimental discovery of superconductivity in boron-doped diamond has attracted considerable attention [1,2]. However, until present time, there is no evident explanation of how boron atoms are incorporated into the diamond crystal lattice and what the structure of the doped crystal is. In the present study, basing on our experimental data, we propose a way boron incorporates into the diamond crystal lattice. TEM studies of the boron doped diamond (BDD) were performed using a JEM-2010 high resolution electron microscope with a GIF Quantum attachment for EELS. The diamond surface was studied by JEM-7600F and by the fluorescence. Fig. 1 shows a (111) facet of BDD with a small boron concentration. The surface represents triangles. This contrast disappears after the polishing. It was found that the thickness of the layer, which is responsible for the contrast, is not more than 1 micron. The majority of the research works on BDD performed their experiments on the polycrystalline diamond. This can be one of the reasons why such contrast on the diamond (111) surface was not reported earlier. Boron distribution in the diamond was realized in two ways. Fig. 2 shows a high resolution image of a diamond crystal lattice with zone axis [110]. The irregularity of the crystal lattice and a noticeable change in contrast are seen in the horizontal band in the middle of the image (this band consist of several {111}-layers). The EEL spectrum obtained from this area has shown that the boron atomic content was approximately 2.5 atomic %. Apparently, boron forms point defects, which accumulate and form such seams as in Fig. 2,

parallel to one of {111} planes. Planes ( 111 ), ( 111 )

and ( 111 ) compose 70.52° with the upper facet (111). These three planes intersect with (111) at <110> directions, which compose a 60°-angles. Since boron atoms spread in the diamond along {111} planes, the areas where boron atoms are present will be bordered by intersections of different {111} planes. All these boundaries compose 60°-angles and are seen as equilateral triangles. Fast Fourier transform from 2 is shown in the inset. Besides the main diamond reflections, the given diffraction pattern includes some additional spots indicating a narrow boron-doped diamond layers. The second option of boron presence in the sample is the boron carbide formation. We have created a stereographic projection of two phases matching: diamond and B4C based on the analysis of all the diffraction patterns. Orientation relationship between the diamond and boron carbide lattices looks as the following: (1-10)diam II (01-10)B4C и [001]diam II [0001]B4C.

References

[1] Ekimov E.A. et. al., Nature, 428, 2004, 542-545 [2] Ohta Y., New diamond and frontier carbon

technology, 17, 2007, 33-44

B.A. Kulnitskiy, I.A. Perezhogin, S.A. Terentiev, S.A. Nosukhin, M.S.Kuznetsov, V.D. Blank [email protected]


Figure 1. Fluorescence of the boron-doped diamond surface (111) in ultraviolet (wavelength 225 nm). There can be seen numerous triangles in this image, which sides are parallel to the intersections of {111} planes.

Figure 2. High resolution transmission electron microscopy image of the diamond lattice, zone axis [110]. There are some irregularity of the lattice ({111} planes) and change in contrast in the horizontal band in the middle of the image; FFT from a) is shown in the inset.

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Nanobiosensors and Bioanalytical Applications Group. Institut Català de Nanociencia i Nanotecnología (ICN2) CSIC and CIBER-BBN, Barcelona, Spain

The dream of having a device in the palm of our hand able to deliver an instant diagnostics of our health status could become a reality soon thanks to the last advances in nanomedicine, nanobiosensors and lab‐on-a‐chip which promise to surpass the existing challenges, opening the door to a global health access. Such point-of-care (POC) diagnostic tools could afford the identification of any disease (as cancer) or any alteration in our cellular pathways at the earliest stage possible in a fast, simple and cost-effective way. Nanophotonic biosensors (mainly those based on nanoplasmonics and silicon photonics) have revealed themselves as promising candidates for achieving truly point-of-care devices. Advantages as miniaturization, sensitivities clinically relevant, integration capabilities, reliability, and potential for multiplexing can be offered by these nanophotonic technologies [1]. The main objective of our research is to achieve such ultrasensitive platform for POC label-free analysis accomplishing the requirements of disposability and portability. Figure 1 shows a scheme of the POC platform we envisioned as our main goal. The platform includes nanophotonic biosensors integrated with microfluidics (see Fig. 2), diffractive nanogratings for incoupling in the sub-micron channels, custom-designed read-out methods (as photodetectors or CCD), data acquisition and processing electronics. The nanophotonic sensors are based on novel nanophotonic bimodal

interferometric waveguides (patents granted) [2] based on silicon technology which have, as main characteristic, an extreme sensitivity. Noticeably, we have implemented a first POC laboratory prototype which allows the label-free detection of biomolecular interactions with extreme sensitivity [3]. Most relevant, we have recently demonstrated its ability to directly detect human hormones at physiological levels in human fluids (below 0.1 pg/mL) or microorganisms (at very few cfu/mL) through the immunointeraction with their specific antibodies.

References

[1] M.C. Estevez, M. Álvarez and L. M. Lechuga. Laser & Photonics Reviews, 6 (4), 463 (2012)

[2] EP2278365;PCTES08070142;US20110102777 [3] D. Duval et al. Lab on chip 12 (11) 1987 (2012).

Figure 1. Scheme of the LOC platform based on nanophotonic interferometric sensors.

L. M. Lechuga [email protected]


Figure 2. Photograph of one chip containing 16 nanophotonic sensors integrated with a polymer microfluidics network.

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ICN2 - Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) Spain

Unconventional magneto-transport fingerprints in the quantum Hall regime (with applied magnetic field rom one to several tens of Tesla) in chemically functionalized graphene are reported [1]. The scattering otential induced by the impurities is modeled by tight-binding parameters extracted from ab initio alculations [2], which, in turn, are used inside an efficient real space order N method [3] to calculate the issipative conductivity [4] under high field. Upon chemical adsorption of monoatomic oxygen (from 0.5% to few percents), the electron-hole symmetry of Landau levels is broken, while a double-peaked onductivity develops at low-energy, resulting from the formation of critical states conveyed by the andom network of defects-induced impurity states. Scaling analysis suggests an additional zero-energy uantized Hall conductance plateau, which is here not connected to degeneracy lifting of Landau levels y sublattice symmetry breakage. This singularly contrasts with usual interpretation, and unveils a new layground for tailoring the fundamental characteristics of the quantum Hall effect.

References

[1] N. Leconte, F. Ortmann, A. Cresti, J.-C. Charlier, and S. Roche, accepted in 2D Materials (2014)

[2] N. Leconte; A. Lherbier, F. Varchon, P. Ordejon, S. Roche, and J.-C. Charlier, Phys. Rev. B 84 2011) 235420; N. Leconte, J. Moser, P. Ordejon, H.H. Tao, A. Lherbier, A. Bachtold, F. Alsina,

C.M.S. Torres, J.-C. Charlier, and S. Roche, ACS Nano 4 (2010) 4033

[3] H. Ishii, F. Triozon, N. Koboyashi, K. Hirose, and S. Roche, C.-R. Physique 10 (2009) 283

[4] D. Soriano, N. Leconte, P. Ordejon, J.-C. Charlier, J.J. Palacios, and S. Roche Phys. Rev. Lett. 107 (2011) 016602; N. Leconte, D. Soriano, S. Roche, P. Ordejon, J.-C. Charlier, and J.J. Palacios, ACS Nano 5 (2011) 3987

Nicolas Leconte, Frank Ortmann, Alessandro Cresti, Jean-Christophe Charlier and Stephan Roche [email protected]

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University of Siegen, Graphene-based Nanotechnology Hölderlinstr. 3, 57076 Siegen, Germany

This talk will discuss the opportunities and challenges for applications of graphene and 2D materials beyond field effect transistors. First, hot electron transistors with graphene components will be introduced that are projected to allow THz operation [1], [2]. Next, I will present examples for graphene / silicon and molybdenum / silicon heterojunctions as photodetectors [3]. Finally, the low mass of graphene makes it interesting for nanoelectromechanical systems. This will be discussed using the example of graphene membrane based piezoresistive pressure sensors [4], [5]. These potential future devices can be categorized as “More-than-Moore” applications, which add functionality to the existing silicon CMOS technology.

References

[1] W. Mehr, J. C. Scheytt, J. Dabrowski, G. Lippert, Y.-H. Xie, M. C. Lemme, M. Ostling, and G. Lupina, “Vertical Transistor with a Graphene Base,” IEEE Electron Device Lett., vol. 33, pp. 691–693, 2012.

[2] S. Vaziri, G. Lupina, C. Henkel, A. D. Smith, M. Östling, J. Dabrowski, G. Lippert, W. Mehr, and M. C. Lemme, “A Graphene-based Hot Electron Transistor,” Nano Lett., vol. 13, p. 1435−1439, 2013.

[3] C. Yim, M. O’Brien, N. McEvoy, S. Riazimehr, H. Schäfer-Eberwein, A. Bablich, R. Pawar, G. Iannaccone, C. Downing, G. Fiori, M. C. Lemme, and G. S. Duesberg, “Heterojunction Hybrid Devices from Vapor Phase Grown MoS2,” Sci. Rep., vol. 4, Jun. 2014.

[4] A. D. Smith, S. Vaziri, F. Niklaus, A. C. Fischer, M. Sterner, A. Delin, M. Östling, and M. C. Lemme, “Pressure Sensors based on Suspended

Graphene Membranes,” Solid State Electron., 2013.

[5] A. D. Smith, F. Niklaus, A. Paussa, S. Vaziri, A. C. Fischer, M. Sterner, F. Forsberg, A. Delin, D. Esseni, P. Palestri, M. Östling, and M. C. Lemme, “Electromechanical Piezoresistive Sensing in Suspended Graphene Membranes,” Nano Lett., vol. 13, no. 7, pp. 3237–3242, Jul. 2013.

Max Lemme [email protected]

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DIPC (Donostia International Physics Center) Paseo Manuel de Lardizabal, 4 20018 Donostia-San Sebastián (Gipuzkoa), Spain The Bethe-Salpeter equation (BSE) is the state of the art for computing optical spectra for solids and molecular clusters. Here we present an implementation of BSE for clusters that scales asymptotically like O(N^3) with the number of atoms, achieved by exploiting the locality of the problem in the local basis set representation and by using the Haydock recursion method to compute the spectrum. Using a pseudhermitian Lanczos algorithm we can go beyond the Tamm-Dancoff approximation within our iterative scheme. As a starting point for the BSE we compute quasiparticle energies with our low-scaling GW implementation [1], retaining the frequency dependence of all quantities and thus avoiding the plasmon-pole model or similar schemes. The initial wave functions are taken from a preceding SIESTA calculation. We discuss the influence of self-consistency on the quasiparticle energies [2] and its effect on the BSE spectra. We also investigate the satellite peaks that are present in the GW density of states. Computed GW/BSE spectra are shown for some organic molecules of medium size that are relevant for photovoltaic applications.

References

[1] D. Foerster et al. J. Chem. Phys. 135 (2011) 074105.

[2] P. Koval et al. Phys. Rev. B 89 (2014) 155417.

Mathias P. Ljungberg, Peter Koval, Francesco Ferrari, Dietrich Foerster and Daniel Sánchez-Portal [email protected]


1Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain

2Institut de Microelectrònica de Barcelona- Centre Nacional de Microelectrònica,

Campus UAB, 08193 Bellaterra, Spain 3MATGAS, Campus UAB, 08193 Bellaterra, Spain

Thermoelectric materials permit the direct conversion of waste heat recovering useful energy as electricity. Nowadays these materials are not competitive in terms of efficiency with conventional thermal machines when large amount of energy are required, but thanks to their simplicity can offer an alternative in small-scale application or when mobility is required [1]. In thermoelectric materials the efficiency in energy conversion can be described through the figure of merit ZT, defined as

Nanostructured semiconductors offer a promising route towards the fabrication of miniature chip-based TE devices. In particular, Si has emerged as a potential TE candidate since the discovery that small diameter nanowires (NWs) conduct heat like a disordered solid ( ↓) [1], maintaining reasonable values for both electrical conductivity (σ) and Seebeck (S) coefficient. Consequently it is expected an enhancement of the thermoelectric conversion efficiency. In this context, the fabrication of miniature chips formed by Si NWs arrays may yield efficient conversion devices. While bottom-up strategies for the synthesis of NWs allow the realization of highly-dense large-area arrays of NWs [2], they often lack enough reproducibility. Here, we present a planar TE microgenerator based on top-down fabricated that can work up to T ~ 700 K. The design is based on a free-standing membrane, that should act as a cold or heat removal sink, suspended from a bulk Si frame, acting as heat source, through silicon thin films (100nm thick) with regions doped p and n (see figure 1). This structure is achieved by using CMOS

compatible microfabrication techniques starting with a SOI wafer. To obtain the appropriate doping level we carried out detailed TRIM simulations and multiple implantation and annealing experiments. Doping levels in the range of 1-5x1019 at/cm3 both in n and p-type regions are obtained and epitaxial re-crystallization of the 100 nm thick Si layer is reached during post-implantation thermal treatments. Suitable electrical contact resistances, i.e. 1.5x10-5 Ωcm2, were achieved by using 100nm Ni thin layers and post-deposition annealing to form NiSi. The microgenerator is equipped with Au heater/sensors, placed in membrane and Si frame, to completely determine the thermoelectrical performance of the device (see figure 2). We do obtain an improvement of 50% in the ZT of the whole device compared with the bulk Si values. For T gradients of 200K the device generates more than 4 mW/cm2.

References

[1] Lon E. Bell, Science 321, (2008) 1457-1461. [2] L. Shi, D. Li, C. Yu, W. Jang, D. Kim, Z. Yao, A.

Majumdar, J. of Heat Transfer 125 (2003) 881-888.

[3] D.Davila, A.Tarancón, C.Calaza, M.Salleras, M.Fernandez-Regúleza, A.San Paulo, L.Fonseca. Nano Energy 1 (2012) 812–819.

[4] A.P.Perez-Marín, A.F.Lopeandía, L.Abad, P.Ferrando-Villaba, G.Garcia, A.M.Lopez, F.X.Muñoz-Pascual, J. Rodríguez-Viejo, Nano Energy, 4 (2014) 73-80.

A.F. Lopeandía1, A. Perez-Marin1, Ll. Abad2,3, P. Ferrando1, M. Molina-Ruiz1, G. Garcia1, F. X. Alvarez1, F. X. Muñoz-Pascual2, J. Rodríguez-Viejo1,3 [email protected]


Figure 1. Schematic of the m-TEG.

Figure 2. Thermoelectric generation evaluated using the variable charge loads at different Temperatures.

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Omicron NanoTechnology GmbH - Oxford Instruments Limburger Str 75, 65232 Taunusstein, Germany

A major challenge in the development of novel devices in nano- and molecular electronics is their interconnection with larger scaled electrical circuits. Local electrical probing by multiple probes with STM precision can significantly improve efficiency in analyzing electrical properties of individual structures on the nano-scale without the need of a full electrical integration. We developed a microscope stage that merges the requirements of a SEM navigated 4-probe STM and at the same time satisfies the needs for high performance SPM. Besides SEM/STM probe fine navigation, the excellent STM/AFM performance level of the LT NANOPROBE at T<5K expands applications to tunneling spectroscopy and even the creation or modification of nano-structures by a sharp and precise SPM probe. Extremely low thermal drift competitive to state-of-the-art low temperature STMs allows for sufficient measurement time as needed for experiments on the atomic scale. QPlus NC-AFM imaging with excellent atomic resolution extends the field of applications to non-conducting surfaces. In this contribution we will focus on measurements that prove the performance level of the instrument as well as on tunneling spectroscopy and atom manipulation experiments on Ag(111) .

Figure 1. The LT Nanoprobe stage showing 4 SPM units.

Measurements. a) SEM image of 4 STM probes placed on a Fe-nanowire for 4-point conductance measurements at T < 5 K. b) High resolution STM image of a Ag(111) surface at T<5K. c) Atom manipulation of Ag-particles on a Ag(111) surface at 5K. d) High resolution NC-AFM image of a NaCl(001) surface at T=4.4K.

M. Maier, J. Koeble and J. Chrost [email protected]

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Department of Electronic Engineering, Avda. Paisos Catalans 26, Campus Sescelades, Universitat Rovira i Virgili, Tarragona, Spain

The fabrication of self-ordered nanoporous anodic alumina (NAA) is based on simple, cost-effective, electrochemically anodization of aluminum, which yields vertically aligned, highly-ordered (hexagonal pattern) nanoporous structures [1]. Nanoporous anodic alumina is one of the most promising nanomaterials for developing new applications in biotechnology and nanomedicine for example: molecular separation, drug delivery systems, tissue engineering, etc. NAA presents some advantages in comparison with the well know porous silicon such as greater pH and thermal stability and fabrication flexibility to control pore structures. Its optical and photonic properties such as reflectance, transmittance, absorbance and photoluminescence can be tailored by modifying the pore size and nanostructure [2,3,4]. Furthermore, its high surface area (up to several hundreds of square meters per gram) and easy chemical functionalization allows to design and fabricate nanoporous anodic alumina structures with special features for label-free optical biosensing [5,6]. In a first part, this talk will give an overview of nanoporous anodic alumina properties and several electrochemical approaches for fabricating optical structures such as tunable Fabry - Pérot interferometer, gold-coated double-layer nanoporous, distributed Bragg reflector, nanoporous rugate filter, etc. In a second part, the talk will presents and discuses some examples of label-free optical biosensing for the detection of proteins, enzymes and heavy metals.

References

[1] Ferré-Borrull, J., Pallarès, J., Macías, G., Marsal, L.F., Materials, 7 (2014), 5225.

[2] Macias, G., Hernández-Eguía, L.P., Ferré-Borrull, J., Pallares, J., Marsal, L.F., ACS Applied Materials and Interfaces, 5, (2013) 8093.

[3] Santos, A., Balderrama, V.S., Alba, M., Formentín, P., Ferré-Borrull, J., Pallarès, J., Marsal, L.F., Advanced Materials, 24 (2012), 1050.

[4] Hernandez-Eguia, L. P., Ferre-Borrull, J., Macias, G., Pallares, J., Marsal, L.F., Nanoscale Research Letters, 9, (2014) 414.

[5] Baranowska, M., Slota, A.J., Eravuchira, P.J., Macias, G., Xifré-Pérez, E., Pallares, J., Ferré-Borrull, J., Marsal, L.F., Colloids and Surfaces B: Biointerfaces, 122 (2014) 375.

[6] Santos, A., MacÍas, G., Ferré-Borrull, J., Pallarès, J., Marsal, L.F., ACS Applied Materials and Interfaces, 4 (2012) 3584

Figure 1. SEM images of the cross-sectional view (a) and top view (b) of a nanoproous anodic alumina bilayer (top layer with large pores and a bottom layer with smaller pores). The interfaces a, b, and c represent the zone where the reflections occur resulting in three interfering light beams. (c) Schematic representation of the nanoporous anodic alumina bilayer with trapped proteins in the first layer (top of the structure).

Lluis F. Marsal [email protected]


ICMA-CSIC. University of Zaragoza. Zaragoza (Spain) Shanghai Jiao Tong University. Shanghai (China)

In the last decades, inorganic nanoparticles have been steadily gaining more attention from scientists from a wide variety of fields such as material science, engineering, physics or chemistry. The very different properties compared to that of the respective bulk, and thus intriguing characteristics of materials in the nanometre scale, have driven nanoscience to be the centre of many basic and applied research topics. Moreover, a wide variety of recently developed methodologies for their surface functionalization provide these materials with very specific properties such as drug delivery and circulating cancer biomarkers detection. In this talk we describe the synthesis and functionalization of magnetic and gold nanoparticles as therapeutic and diagnosis tools against cancer: -Pseudo-spherical gold nanoparticles derivatized with with fluorescent dyes, cell penetrating peptides and small interfering RNA (siRNA) complementary to the proto-oncogene myc have been tested using a hierarchical approach including three biological systems of increasing complexity: in vitro cultured human cells, in vivo invertebrate (freshwater polyp, Hydra) and in vivo vertebrate (mouse) model. Selection of the most active functionalities was assisted step by step through functional testing adopting this hierarchical strategy. [1] Merging these chemical and biological approaches lead to a siRNA/RGD gold nanoparticle capable of targeting tumor cells in lung cancer xenograft mouse model, resulting in successful and significant c-myc oncogene downregulation followed by tumor growth inhibition and prolonged survival of the animals. [2] -Gold nanoprisms (NPRs) have been functionalized with PEG, glucose, cell penetrating peptides, antibodies and/or fluorescent dyes, aiming to

enhance NPRs stability, cellular uptake and imaging capabilities, respectively. [3] Cellular uptake and impact was assayed by a multiparametric investigation on the impact of surface modified NPRs on mice and human primary and transform cell lines. Under NIR illumination, these nanoprobes can cause apoptosis. Moreover, these nanoparticles have also been used for optoacoustic imaging, [4] as well as for tumoral marker detection using a novel type of thermal ELISA nanobiosensor using a thermosensitive support. [5] -Magnetic nanoparticles functionalized with DNA molecules and further hybridizing with different length fluorophore-modified DNA have allowed the accurate determination of temperature spatial mapping induced by the application of an alternating magnetic field. [6] Due to the design of these DNAs, different denaturalization temperatures (melting temperature, Tm) could be achieved. The quantification of the denaturalized DNA, and by interpolation onto a Boltzmann fitting model, it has been possible to calculate the local temperature increments at different distances, corresponding to the length of each modified DNA, from the surface of the nanoparticles. The local increments achieved were up to 15ºC, and the rigidity conferred by the double strand DNA allowed to evaluate the temperature at distances up to 5.6 nm from the nanoparticle surface.

References

[1] J. Conde, A. Ambrosone, V. Sanz, Y. Hernandez, F. Tian, P. V. Baptista, M. R. Ibarra, C. Tortiglione, J. M. de la Fuente. ACS Nano, 2012, 6, 8316.

Jesús Martínez de la Fuente


[2] J. Conde, F. Tian, Y. Hernández, C. Bao, D. Cui, M. R. Ibarra, P. V. Baptista, J. M. de la Fuente. Biomaterials. 2013, 34, 7744.

[3] B. Pelaz, V. Grazú, A. Ibarra, C. Magén, P. del Pino, J. M. de la Fuente. Langmuir, 2012, 28, 8965.

[4] C. Bao, N. Beziere, P. del Pino, B. Pelaz, G. Estrada, F. Tian, V. Ntziachristos, J. M. de la Fuente, D. Cui. Small, 2013, 9, 68.

[5] E. Polo, P. del Pino, B. Pelaz, V. Grazu, J.M. de la Fuente. Chemical Communications, 2013, 49, 3676.

[6] JT Dias, M Moros, P del Pino, S Rivera, V Grazu, JM de la Fuente. Angew Chem Int Ed Engl, 2013, 52, 11526.

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European Synchrotron Radiation Facility, 38043-Grenoble, France

Semiconductor nanowires offer new opportunities for optoelectronic and spintronic nanodevices. However, their full potential is ultimately dictated by our ability to control multiple property-function relationships taking place at the nanoscale in the spatial and time domains. Only a combination of highresolution analytical techniques can provide a comprehensive understanding of their complex functionalities. Here we describe how a multimodal hard X-ray nanoprobe (Figure 1) addresses fundamental questions in nanowire research. Selected topics ranging from cluster formation, dopant segregation, and phase separations to quantum confinement effects are investigated with sub-100 nm spatial resolution and sub-50 ps temporal resolution. This approach opens new avenues for structural, composition and optical studies with broad applicability in materials science.

References

[1] G. Martinez-Criado et al., Advanced Materials, DOI: 10.1002/adma.201304345 (2014).

Gema Martinez-Criado, Manh-Hung Chu, Jaime Segura-Ruiz, Damien Salomon, Benito Alén [email protected]


1Departamento Física de la Materia Condensada, Universidad Autónoma de Madrid, E-

28049 Madrid, Spain. 2Present address: II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77,

50937 Köln, Germany. 3Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid,

E-28049 Madrid, Spain. The selective modification of pristine graphene represents an essential step to fully exploit its potential. Two main routes are usually followed to modify graphene properties. On one hand, bottom up approaches have demonstrated to be very efficient to change the overall electronic structure of graphene [1-3]. On the other hand, with top down approaches it is possible to induce such changes on a local scale [4,5]. Here we merge bottom-up and top-down strategies to tailor graphene with nanometer accuracy. Specifically, we have developed a perfectly reproducible nanolithographic technique that allows, by means of an STM tip, to modify with 2.5 nm accuracy the electronic properties of graphene monolayers epitaxially grown on Ir(111) surfaces. This method can be carried out also on micrometer sized regions and the structures so created are stable even at room temperature. As a result, we can strategically combine graphene regions presenting large differences in their electronic structure to design graphene nanostructures with tailored properties. Therefore, this novel nanolithography method could open the way to the design of nanometric graphene-based devices with specific functionalities.

References

[1] R. Balog, B. Jorgensen, et al., Nature Materials, 9, (2010) 315-319.

[2] S. Rusponi, M. Papagno, et al., Physical Review Letters, 105, (2010) 246803.

[3] T. Ohta, A. Bostwick, et al., Science, 313, (2006) 951-954.

[4] M. M. Ugeda, I. Brihuega, et al., Physical Review Letters, 104, (2010) 096804.

[5] L. Tapaszto, G. Dobrik, et al., Nature Nanotechnology, 3, (2008) 397-401

Figure 1. Upper panel illustrates the nanopatterning process, with a schematic STM tip drawn on top of a real experimental image. Lower panel shows a 95x35 nm

2

STM image with the final result after writing the word “graphene”.

Antonio J. Martínez-Galera1,2, Iván Brihuega1,3, Ángel Gutiérrez-Rubio1, Tobias Stauber1,3, José M. Gómez-Rodríguez1,3 [email protected]


ICFO-Institut de Ciéncies Fotoniques, Mediterranean Technology Park, 08860 Casteldefells, Barcelona, Spain

Two-dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDCs) can be assembled on top of one another to create the so called van der Waals (vdW) heterostructures [1]. The properties of these artificial materials can be tailored by combining the various 2D crystals, thus making them promising candidate for multi-functional, high performance optoelectronic applications. Recently, photodetectors with high efficiencies have been demonstrated using graphene /MoS2/graphene [2] and graphene/WS2/graphene heterostructures [3]. However, many questions concerning photoconduction processes occuring in these TMDC-based heterostructure remain unanswered, in particular the role the excitons generation and separation. Here we present a detailed study of the photocurrent generated in graphene /WSe2/graphene heterostructure encapsulated in hBN. By performing photocurrent spectroscopy, we demonstrate that the photoresponse of the heterostructure is strongly dominated by the excitons generated in the TMDC. The electon-hole pairs can be efficiently separated by creating a potential difference between the top and bottom graphene, which also act as electrodes. The sign of the photocurrent can therefore be changed by tuning the Fermi level one of the graphene layer via an external gate. Our results also demonstrate the potential of these heterostructures as photodetectors, with a responsivity of up to 0.1 A/W at 575 nm.

References

[1] Geim et al., Van der Waals Heterostructures, Nature, 2013.

[2] Yu et al., Highly efficient gate-tunable photocurrent generation in vertical heterostructures of layered materials, Nature nanotechnology, 2013.

[3] Britnell et al., Strong light-matter interactions in heterostructures of atomically thin films, Science, 2013.

Mathieu Massicotte, Peter Schmidt and Frank Koppens [email protected]

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Catalan Institute of Nanoscience Nanotechnology, Campus UAB, Bellaterra, Spain ICREA, Institució Catalana de Recerca i Estudis Avancats, Barcelona, Spain

Graphene is increasingly attracting attention and it is under intensive research by biosensing technology community thanks to its interesting chemical, mechanical, electrical and optical properties. Between the various graphene forms, graphene oxide (GO) shows advantageous characteristics as a biosensing platform due to its excellent capabilities for direct wiring with biomolecules, heterogeneous chemical and electronic structure, the possibility to be processed in solution and the availability to be tuned as insulator, semiconductor or semi-metal. Moreover, GO bears the photoluminescence property with energy transfer donor/acceptor molecules exposed in a planar surface and even can be proposed as a universal highly efficient long-range quencher, which is opening the way to several unprecedented biosensing strategies. The possibility to be processed in solution combined with easy chemical or electrochemical reduction makes GO an interesting and advantageous material to fabricate electrodes with various forms and shapes through either ink-jet printing or other simple transferring technologies. Some of our most important and recent graphene-based biosensing systems with interest for health and safety&security will be presented. The developed electrical /electrochemical devices include screen-printed electrodes modified with graphene (for phenolic compounds detection), graphene-based FET (gases detection) as well as transparent & flexible graphene based impedancimetric devices for cell studies. In addition some novel optical-based detection systems that involve graphene will also be described. A graphene-based microarray that can be turned ON by a pathogen will be shown. This system has been designed and evaluated for the sensing of E. coli

bacteria in diverse matrices. It employs antibody–quantum dot probes and exploits the extraordinary two-dimensional structure and fluorescence-quenching capabilities of graphene oxide.

References

[1] E.Morales-Narváez, A.Merkoçi, “Graphene oxide as an optical biosensing platform”, Advanced Materials, Adv. Mater. 2012, 24, 3298–3308.

[2] E.Morales-Narváez, B.Pérez-López, L.Baptista Pires, A.Merkoçi, “Ultrahigher quantum dot quenching efficiency by graphene oxide in comparison to other carbon structures”, Carbon, 50 (2012) 2987–2993.

[3] E.Morales-Narvez, A.R.Hassan, A.Merkoçi, “Graphene Oxide as a Pathogen-Revealing Agent: Sensing with a Digital-Like Response”, Angwandte Chemie 2013, Volume 52, Issue 51,13779–13783. (Pending Patent: EP 13188693.9). (www.nanobiosensors.org).

[4] L. Baptista-Pires, B. Pérez-López, C.C. Mayorga-Martinez, E. Morales-Narváez, N. Domingo, M.J. Esplandiu, F. Alzina, C.M. Sotomayor Torres, A. Merkoçi “Electrocatalytic tune of biosensing response through electrostatic or hydrophobic enzyme – graphene oxide interactions”, Biosensors & Bioelectronics Volume, 2014, 61,655–662.

Arben Merkoçi [email protected]

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Unidad Asociada ICMM/CSIC-UPV, Universidad Politécnica de Valencia, 42022 Valencia (Spain), and Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049 Madrid (Spain)

Recently, we have developed silicon colloids (SCs) [1,2] with particle size between 200 nm and 3000 nm. Silicon has an extremely high refractive index value, so SCs behave as optical microcavities in the near IR region. Here we will report on the following applications. 1. Silicon colloids based Raman enhanced sensors. Silicon colloids have huge values of the light scattering cross section, and therefore a huge the evanescent fields around the nanoparticles. We have developed Raman enhanced chemical sensors based on silicon nanoparticles with Raman signal enhancement factor similar to that shown for gold nanoparticles. At variance to gold silicon is very cheap to produce (1000 times cheaper) and it biodegrades very easily into the natural chemical species (polysilicic acid) of the human body [3]. 2. Silicon colloids based metamaterials. Here we report on the large magnetic response of SNs in the NIR region with small optical losses [2,4]. We also have developed a two dimensional photonic crystal, which shows a perfect optical matching condition in the NIR region. Our findings have important implications in the bottom up processing of large area low loss metamaterials working in the NIR region. 3. Silicon nanocavities for Mie enhanced photodiodes. SCs constitute a very promising platform for developing a p-n junctions solar cells able to overcome the well known classical Shockley–Queisser (SQ) limit [5]. Here we show the first example of a photodiode developed on a micrometer size silicon spherical cavity. The long dwell time of resonating photons enhances the

absorption efficiency of photons at the IR region well below the absorption edge of silicon [6].

References

[1] R. Fenollosa, et al., Adv. Mat. 20, 95, (2008). [2] L. Shi, et al., Adv. Mat., 24, 5934, (2012). [3] I. Rodriguez, et al., Nanoscale (2014) [4] L. Shi, et al., Nature Comm., 4, 1904, (2013). [5] W. Schockley, and H. J. Queisser, J. Appl. Phys.

32, 510, (1961). [6] M. Garin, et al., Nature Comm., (2014).

Figure 1. Spherical nanocavity made of polycrystalline silicon.

F. Meseguer

[email protected]

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1Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, Piazza

San Silvestro 12, 56127 Pisa, Italy 2Graphene Labs, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy

Hexagonal boron nitride (h-BN) is a two-dimensional (2D) insulator that has recently been proposed as the ideal substrate for the development of next generation graphene electronics. Its reticular match with graphene and low interlayer electronic coupling have already been shown to positively impact graphene mobility [1]. In order to move towards a more scalable approach, several groups have attempted to grow graphene directly on h-BN via chemical vapor deposition (CVD) [2-3]. However, h-BN is a poor catalyst for graphene growth and the mechanisms beyond the growth process as well as the structural properties of the grown graphene should be thoroughly investigated. In this work we select single crystal h-BN flakes as the perfect playground - rather than the often defective and nano crystalline CVD grown h-BN - for graphene growth investigations. We adopt a short and catalyst free process to grow graphene directly on exfoliated h-BN flakes via chemical vapor deposition (CVD). We observe that graphene tends to nucleate in circular shaped pads and we show that - by varying the growth parameters - the size of such pads can be increased to about 1 micron. This value is about 1 order of magnitude higher than that previously reported by other groups [2-3]. By prolonging growth time the pads merge to form a continuous graphene film. The structural and morphological properties of graphene are investigated by scanning electron microscopy (SEM), Raman spectroscopy, and atomic force microscopy (AFM). In this study particular attention is posed on the chemical and structural properties of the interface between graphene and h-BN.

Keywords: Graphene; hexagonal Boron Nitride(h-BN); Chemical vapor deposition method; SEM, Raman spectroscopy and AFM.

References

[1] C.R. Dean et al., Nature Nanotechnology 5 (2010) 722-726.

[2] M. Wang et al., Advanced Materials 25 (2013) 2746-2752.

[3] M. Son et al., Nanoscale 3 (2011) 3089-3093.

Figure 1. SEM micrograph of graphene pads grown on exfoliated h-BN by chemical vapor deposition method. The origin of the mosaic contrast on h-BN will be discussed in this work.

N. Mishra1, V. Miseikis1, D. Convertino1, M. Gemmi1, V. Piazza1 and C. Coletti1,2 [email protected]


Physical Review Letters

Though the focus of related research has been changing, each year both PRL and Phys. Rev. continue to receive hundreds of papers on graphene-based topics. PRL’s acceptance rate for papers in all areas of physics has dropped in recent months. In this context I will present some information and data regarding what the journal receives, publishes, and intends to publish in the areas of graphene and related 2D materials.

Samindranath Mitra

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1

Physics Department, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain

2 Institut NEEL CNRS/UJF, 38042 Grenoble cedex 9, France

3 BioMems, CNM-IMB, Campus UAB, 08193 Bellaterra, Spain

4 Matgas Research Centre, Campus UAB, 08193 Bellaterra, Spain

The use of membrane-based chip calorimeters has opened the way of studying size dependence of thermodynamic properties in nanomaterials. Among the different calorimetric methods implemented for chip, quasi-adiabatic nanocalorimetry [1] reports the better sensitivity per unit area, but do not offers the possibility of measuring heat capacity at constant temperatures as function other variables (time, magnetic field…) like AC-calorimetry [2]. We present a new operational method combining the better characteristics of both methods previously mentioned. In this method, the calorimetric cell, consisting of a silicon nitride membrane (~ 180nm thick) and a thin film metallic sensor, is heated by joule effect with train of current pulses (few μs width, ms separated) promoting local temperature scans that span few K over the base temperature. The possibility of multiple scan averaging and the huge heating rates accessible (up to 106 K/s) permits to reach exceptional heat capacity resolution of 100 pJ/(mm K √Hz). The method is demonstrated by characterizing the antiferromagnetic transition in CoO thin film samples of 5 and 20 nm thick.

References

[1] S. L. Lai et al., Appl. Phys. Lett., 67, 9 (1995), p1229.

[2] P. F. Sullivan et al., Phys. Rev., 173, 3, (1968), p679.

M. Molina-Ruiz1, A. F. Lopeandía1,2, Ll. Abad3, G. Garcia1, O. Bourgeouis2 and J. Rodríguez-Viejo1,4 [email protected]

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1International Center for Young Scientists (ICYS), National Institute for Materials Science

(NIMS), 1-2-1 Sengen Tsukuba, Ibaraki 305-0047, Japan

2National Institute for Materials Science (NIMS), 1-2-1 Sengen, 305-0047 Tsukuba, Japan

3Catalan Institute of Nanoscience and Nanotechnology (ICN2), Bellaterra

(Barcelona), 08193, Spain 4Charles University, V Holesovickach 2, Praha 8, Czech Republic

Intramolecular resolution accomplished by atomic force microscopy (AFM) has recently attracted considerable attention [1,2] because its potential to unveil the chemical structure of unknown molecules [3], characterise charge distributions [4] and bond ordering [5] within molecules, as well as to study chemical transformations [6,7] and intermolecular interactions [8,9]. So far, most of these achievements make use of planar molecules because high-resolution imaging of three-dimensional (3D) surface structures with AFM remains challenging. Here we present a general method for sub-molecular imaging of non-planar molecules and the study of 3D surface systems with atomic resolution using a cantilever-based AFM. We demonstrate this method by characterising the step-edges of a TiO2(101) anatase surface at atomic scale, by simultaneously visualising the chemical structure of a pentacene molecule together with the atomic positions of the substrate [Fig.1 left] , and by resolving the chemical structure of a C60 molecule [Fig. 1 right] with intra-molecular resolution.

References

[1] L. Gross et al., Nature Chemistry 3, (2011) 273. [2] L. Gross et al., Science 325, (2009) 1110. [3] L. Gross et al., Nature Chemistry 2, (2010) 821. [4] F. Mohn et al., Nature Nanotechnology 2,

(2010) 821. [5] L. Gross et al., Science 337, (2012) 1326. [6] D.G. de Oteyza et al., Science 340, (2012) 1434. [7] F. Albrecht et al., J. Am. Chem. Soc. 135, (2013)

9200.

[8] S. Kawai et al., ACS Nano 7, (2013) 9098. [9] J. Zhang et al., Science 342, (2012) 611

Figure 1. Atomic force microscopy images displaying intramolecular resolution in individual pentacene (left) and C60 (right) molecules (3x3 nm

2).

César Moreno1,2,3, Oleksandr Stetsovych2,4, Tomoko K. Shimizu2 and Oscar Custance2 [email protected]

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1Departament de Física Fonamental, Institut de Nanociència i Nanotecnologia,

Universitat de Barcelona, Barcelona (Spain) 08028 2Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Madrid (Spain) 28049

Magnetic nanoparticles (MNPs) are attractive materials object of many studies in the recent past years due to their potential applications in nanotechnology, such as data storage, magnetic resonance imaging, catalysis or environmental remediation [1], and in biomedicine, including biomolecule detection, magnetic hyperthermia or targeted drug delivery [2]. Not only reliable and reproducible methods of nanocrystal synthesis are of key importance in order to obtain uniformly sized MNPs but also high resolution characterization techniques with accurate magnetic sensitivity are necessary to unveil their domain configurations and magnetization reversal processes. In this work, we present synthesis [3] and magnetic domain characterization of Fe3-xO4 nanoparticles – ranging from 15 to 100 nm – by organic decomposition methods, using iron (III) acetylacetonate as precursor and decanoic acid as surfactant and stabilizer. Domain structure of clusters and individual nanoparticles were obtained by magnetic force microscopy (MFM) under variable in-plane or out-ofplane magnetic fields. In addition, micromagnetic simulations were performed with the OOMMF code to help with the interpretation of the sometimes non-trivial contrast in MFM images. Furthermore, some hints are provided about artifacts that might be present when measuring magnetic nanoparticles with MFM, such as influence of the topography and/or electrostatic overlap [4]. Their contribution should be taken into ccount for a correct interpretation of MFM data.

The financial support of the Spanish MINECO through projects MAT2012-33037 and CSD2010-00024, Catalan DURSI 2009SGR856 project and the European Union FEDER funds are acknowledged.

References

[1] C. Sun et al., Advanced Drug Delivery Reviews 60 (2008) 1252-1265

[2] R. Mejías et al., Nanomedicine 5 (2010) 397-408

[3] P. Guardia et al., Langmuir 26 (2009) 5843 / P. Guardia et al., Chem. Comm. 46 (2010) 6108

[4] D. Martínez-Martín et al., Phys. Rev. Lett. 105 (2010) 257203/ M. Jaafar et al., Beilstein Journal of Nanotechnology 2 (2011) 552-560.

Figure 1. (a) Topography of a single Fe3-xO4 nanoparticle (d≈30 nm). MFM images show different orientations of a single domain (b) at remanence and under horizontal fields of (c) + 23 mT and (d) -23 mT.

C. Moya1, Óscar Iglesias-Freire2, N. Pérez1, X. Batlle1, A. Labarta1 and A. Asenjo2 [email protected]

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Pyrenean Institute of Ecology (CSIC), Av. Montañana 1005, 50059 Zaragoza, Spain

Developments in nanotechnology are leading to a proliferation of consumer products containing nanomaterials (NM). These products are likely to become a source of nanoparticles to the environment (Fig. 1) where their possible impacts are largely unknown [1]. There are no specific regulations covering nanomaterials in the European Union, and the use and disposal of these materials is ruled by separate regulations, including REACH. Current regulations usually assimilate nanomaterials to bulk materials from which they are formed. However, nanomaterials exhibit novel and unexpected physicochemical properties, as well as some unusual biological effects. Current standard procedures for environmental risk assessment rely on a set of standardized ecotoxicity tests that may not be adequate for NM [2]. For example, there are concerns that existing protocols may not account for aspects of dosimetry and dispersion of NM, and that some new biological measurements may be needed in some tests. Many challenging questions remain unanswered [3], among them: a) the physical and chemical characterization of the NMS in relevant media; b) the mechanisms allowing NM physically to destroy or pass through cellular membranes and cell walls; c) the specific properties that are related to NM toxic effects, and d) the mechanisms underlying NM trophic transfers. The multidisciplinary approaches needed to address these questions stress the importance of collaborative efforts between ecotoxicologists, biologists, chemists, biophysicists and analytical researchers with groups that develop NM, and the companies that incorporate them into consumer products. This talk will show how to address the

toxicity one of the most currently used materials: silver nanoparticles, as a good example of all the issues presented above. Direct vs. indirect effects and the role played by different chemicals used as coatings for nanoparticles will be presented [4].

References

[1] Navarro, E., et al., Environmental behavior and ecotoxicity of engineered nanoparticles to algae, plants, and fungi. Ecotoxicology, 2008. 17(5): p. 372-386.

[2] Handy, R.D., et al., Practical considerations for conducting ecotoxicity test methods with manufactured nanomaterials: what have we learnt so far? Ecotoxicology, 2012. 21(4): p. 933-972.

[3] Behra, R. and H. Krug, Nanoecotoxicology - Nanoparticles at large. Nature Nanotechnology, 2008. 3(5): p. 253-254.

[4] Navarro, E., et al., Toxicity of Silver Nanoparticles to Chlamydomonas reinhardtii. Environmental Science & Technology, 2008. 42(23): p. 8959-8964.

Figure 1. Chain of events linking the sources of NMs with their environmental impacts, and the relevant research questions at each step.

Enrique Navarro [email protected]


IBM Research – Zürich, Säumerstrasse 4, CH- 8803 Rüschlikon, Switzerland

Direct visualistion and manipulation of nanomaterials at atomic-length scales is a well established process using scanning probe microscopy operated under ultra-high vaccum at cryogenic conditions. It would be highly desirable to achieve similar resolution under standard operating conditions at room-temperature, which will have a direct impact during nanoscale device engineering. We report on real-space imaging of single-molecular and atomic-scale materials in a liquid environment at room-temperature with striking spatial and energy resolution. The structure, intermolecular interactions [1] and energy levels of single-molecules on ultra-flat metals are mapped in liquids using scanning tunneling microscopy and spectroscopy In addtion to single-molecules we extend our approach in resolving atomic positions and electronic bandstructure of single-atom thick materials such as graphene on metals [2] in high-density liquids. We quantitatively map bond-distances and point-defect density on monoatomic graphene and discuss possibilities in tuning atomic-scale contrast with chemically terminanted d-band metal probes.

References

[1] Peter N. Nirmalraj, Heinz Schmid, Bernd Gotsmann and Heike Riel, Langmuir, 29, (2013) 1340-1345.

[2] PN Nirmalraj and HE Riel, Materials Today, 17 (2013), 203-204.

Peter Nirmalraj, Bernd Gotsmann and Heike Riel [email protected]

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1Departamento de Física Aplicada (Universidad de Alicante), Carretera San Vicente del

Raspeig s/n – 03690, San Vicente del Raspeig (Alicante), Spain 2Fachbereich Physik (Universität Konstanz), Universitätsstraße 10 D-78464, Konstanz,

Germany

The study of electron transport in conducting materials at the nanoscale can be carried out by using Scanning Tunneling Microscope (STM) and Mechanically Controllable Break Junction techniques (MCBJ) [1]. At such scales, Kondo effect vanishes the magnetic properties of the 3d transition metals Fe, Co and Ni [2]. The 4f rare earth metals are an interesting aim of study because of their strong magnetic properties among other things. At our laboratories we have measured gadolinium with both STM and MCBJ techniques. In the spectroscopy measurements of this material we perceive a set of features that could be related to its magnetic properties. The interplay between the 4f7 and 5d1 orbitals from Gd drives us to pose the mechanisms that are involved in the electronic transport properties of these systems.

References

[1] N. Agraït, A. Levy-Yeyati, J.M. van Ruitenbeek. Phys. Rep. 377 (2003), 81.

[2] M. R. Calvo et al., Nature 458 (7242) (2009), 1150-1153.

Figure 1. Gd>Gd measurements taken using STM at cryogenic conditions and at zero applied magnetic field. Different distance between tip and sample for every color curve.

Figure 2. Gd>Gd measurements taken using MCBJ at cryogenic conditions. Different values of the applied magnetic field for every color curve. Splitting of the Kondo resonance peak increases with magnetic field.

B. Olivera1,2, E. Scheer2 and C. Untiedt1 [email protected]

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1attocube systems AG, Königinstraße 11a, 80539 München, Germany

2Physics Department, Technical University of Munich (TUM), James-Franck-Str. 1, 85748

Garching, Germany. 3Walther Meissner Institute, Bavarian Academy of Sciences and Humanities, 85748

Garching, Germany.

We report on state-of-the-art scanning probe microscopy measurements performed in a pulse tube based top-loading closed-cycle cryostat with base temperatures down to 1.5K and a 9T magnet [1]. We introduced measures to reduce the level of mechanical and acoustic noise coupling into the system to enable scanning probe experiments. To demonstrate the extremely low vibration amplitudes in our system, we successfully imaged the 0.39 nm lattice steps on single crystalline SrTiO3, as well as magnetic vortices in a high-Tc superconductor (Bi2Sr2CaCu2O8+x). Fine control over sample temperature and applied magnetic field further allowed us to probe the helimagnetic and the skyrmion-lattice phases in Fe0.5Co0.5Si with unprecedented signal-to-noise ratio of 20:1 (see Fig. 1). Finally, Piezo-response Force Microscopy (PFM) was demonstrated on a thin film of BFO in a read and write experiment at low temperatures, as well as on TmFe2O4 at 100 K as a function of magnetic field (+/-9 T).

References

[1] F.P. Quacquarelli, J. Puebla, T. Scheler, D. Andres, C. Bödefeld, B. Sipos, C. Dal Savio, A. Bauer, C. Pfleiderer, A. Erb, and K. Karrai, arXiv:1404.2046v1 (2014).

Figure 1. Large range MFM scan at low temperature of Fe0.5Co0.5Si. The helimagnetic structure is clearly visible as a stripe pattern with a periodicity of approx. 100 nm. This is in good agreement with the expected value (raw, unfiltered data).

F. Otto1, F.P. Quacquarelli1, J. Puebla1, T. Scheler1, D. Andres1, C. Bödefeld1, B. Sipos1, C. Dal Savio1, A. Bauer2, C. Pfleiderer2, A. Erb3 and K. Karrai1 [email protected]

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1Department of Electronics, Bioelectronics and Nanobioengineering Research Group (SIC-

BIO), University of Barcelona, Martí i Franquès 1, Planta 2, Barcelona, Spain 2IBEC-Institute for Bioengineering of Catalonia, Nanosystems Engineering for Biomedical

Applications Research Group, Baldiri Reixac 10-12, Barcelona, Spain 3CIBER-BBN-Biomedical Research Networking Center in Bioengineering, Biomaterials

and Nanomedicine, María de Luna 11, Edificio CEEI, Zaragoza, Spain

We are at beginning of a new European Commission’s initiative. Horizon 2020 is the biggest financial program for Research and Innovation which goes “From fundamental research to market innovation” involving the entire innovation chain. With over 74 billion euros budget, H2020 search turning scientific breakthroughs into innovative products and services [1]. All innovative projects will include a risk management strategy to address at an early stage the risk. H2020 is focused on three fundamental pillars: Scientific Excellence, Society Challenges and Industrial Leadership. This last one aims to support SMEs in the industrial development and application of Key Enable Technologies (KETs), considered crucial accelerators for innovation and competitiveness [2]. Six KETs have been selected as the most strategically relevant: Nanotechnology, Biotechnology Industry, Advanced Materials, Micro & Nano Electronics and Advanced Manufacturing Systems. One of the most promising is Nanotechnology due to its economic and social growth potential. Individually, each KET has a huge potential, however, their crossfertilization is particularly important since their combination offer even greater possibilities to foster innovation and create new markets. The relevance of this combining process relies on the creation of new unique product properties and technology features, which could not have been possible to obtain with a single technoloy. In the healthcare domain, nanobiotechnology and nanomedicine application areas of multi-KETs in a short (2017) and medium

term (2020), are principally based on more efficient and less invasive drugs and therapies, devices and systems for targeted diagnostics and personalized medicine, and smart systems and robots for healthcare services (Figure) [3]. In this context, this paper aims to analyze the current situation of Nanobiotechnology and Nanomedicine innovation within the Spanish National Innovation System. Specifically, the authors want to focus on the commercialization perspectives for healthcare applications and how to reduce the gap between academic research and marketable applications. Among all the indicators analyzed, the authors emphasize the Global Entrepreneurship Monitor [4], the Innovation Efficacy Index [5], the European Regional Competitiveness Index [6] and the GERD [7]. Furthermore, Spanish performance regarding publication and patenting activities are analyzed. At present, the emerging sector of applied nanotechnology is addressed to the biomedicine (Nanobiotechnology and Nanomedicine), starting to show a promising impact in the health sciences principally in three main areas: Diagnostics, Therapeutics and Regenerative Medicine. Nanomedicine is considered a long-term play in the global market; in fact, is anticipated to grow around 25% by year. The global market volume in KETs is 646 billion € and substantial growth expected is approximately an 8% of EU GDP by 2015. About one third of the budget assigned to KETs will be address to support innovative projects integrating

Cristina Paez-Aviles1, Esteve Juanola-Feliu1 and Josep Samitier1,2,3 [email protected]


different KETs. By this year, it was expected that 16% of goods in healthcare and life sciences will incorporate emerging technologies [8]. The expected market size related to radical innovation-based nanomedicines will be 1.000 M€ in 2020 and 3.000 M€ in 2025 [9]. In this context H2020 will spend 9.7% of the total budget in Health, Demographic Change and Wellbeing; specifically, the program will invest 3.851 M€ in Nanotechnology and 516 M€ in Biotechnology Industry [10]. Finally, an analysis of the state-of-the-art of these technologies and their innovation performance environment within an innovation ecosystem of a 5-helix model is crucial to identify strengths and to improve weaknesses facing new scientific and market challenges.

References

[1] E. Commission, “Preparing for our future: Developing a common strategy for key enabling technologies in the EU,” 2009.

[2] ECSIP consortium, “Study on the international market distortion in the area of KETs: A case analysis,”no. May, 2013.

[3] European Commission, [Online]. Available: http://ec.europa.eu/enterprise/sectors/ict/key_technologies/ro-ckets/index_en.htm. [Accessed: 19-May-2014].

[4] J. Amorós and N. Bosma, 2014. [5] S. Mahroum and Y. Al-Saleh, Technovation, 33

(2013) 320–332. [6] European Commission, Regional Innovation

Scoreboard 2012. 2012. [7] D. Kalisz and M. Aluchna, Eur. Integr. Stud. 6

(2012) 140-149. [8] Morrow Jr, R. Bawa, and C. Wei, Med. Clin.

North Am., 91 (2007) 805–843. [9] European Commission, “Roadmaps in

Nanomedicine towards 2020,” 2009. [10] European Commission, “SME opportunities in

Horizon 2020,” 2013.

Figure 1. Field for cross-cutting KETS developments on Healthcare (Source: Ro-cKETs Project Conference, Brussels 2-3 April, 2014).

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1CNRS, IM2NP UMR 7334, Aix-Marseille Université, Campus de St Jérôme 13397

Marseille cedex 20, & ISEN-Toulon, Maison des Technologies, Pl. G. Pompidou F-83000 Toulon, France 2Laboratory of Innovation in Surface Chemistry and Nanosciences (LICSEN),

DSM/IRAMIS/NIMBE CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France

Molecular memory cells are likely to be among the most basic and important components of future molecule-based electronic devices. [1]. For instance a possible architecture for resonant tunnelling diodes consists in a self-assembled monolayer

(SAM) of sigma-pi-sigma (--) organic molecules

composed of alkyl-chains () acting as tunnel

barriers while a central -conjugated moiety acts as a potential well [2]. In this work, we focused on SAMs of specially synthesized new organic molecules based on donor terthiophene (3T) or acceptor naphthalene tetracarboxydiimide (NaPh)

central -conjugated cores with carbon alkyl chains at both sides, grafted on gold through a thiolate. Water contact angles of 100-108° consistent with methyl end-groups on top of the SAM, and infrared and X-ray photoelectron spectroscopy reveal close-packed upright molecules. Scanning tunneling microscopy (STM) shows domains with typical hexagonal ordering [3] for 3T SAMs due to the flexibility given by the alkyl chain, but no NaPh molecular organization could be observed the latter being hindered by the larger NaPh core. Local current-voltage (I-V) characteristics performed under STM tip either on single 3T or NaPh SAMs, or on binary alkylthiol/3T or alkylthiol/NaPh SAMs are shown to correlate well with macroscopic I-V curves measured using eutectic GaIn contacts and to be related with the intrinsic electrical properties of molecules. Contrary to alkylthiol SAMs that exhibit symmetric I-V curve, donor or acceptor type of 3T or NaPh SAMs is revealed by opposite current rectifications. I-V curves were analyzed by Transition Voltage Spectroscopy (TVS) in which the voltage VT at the minimum of the Fowler-Nordheim plot (ln(I/(V²) vs 1/V) is proportional to the energy barrier [4]. For alkylthiol SAMs we found VT~1.1-1.4V, close to that reported by Beebe et al. [4].

HOMO and LUMO positions of the SAMs were extracted using UV photoelectron (UPS) and inverse photoemission spectroscopy (IPES) respectively. From measured values, we show that VT obtained for the various molecules (0.5-1.1V) corresponds with the bias necessary to reach the tail of the HOMO or LUMO density of states closest to the Fermi level, as proposed in the literature [5]. At last, most importantly we show from the SAMs of the various studied molecules that the better structured the SAMs the narrower the distribution of their transition voltage VT obtained by TVS, thus giving evidence of a relationship between structural and electrical properties. We acknowledge support from ANR-11-BS10-012 (SAGe III-V project) and SCS competitive cluster.

References

[1] R.L. Carroll, C.B. Gorman, Angew.Chem.Int.Ed. 41 (2002) 4378.

[2] D. Guérin et al., J.Mat.Chem. 20 (2010) 2680. [3] A. Ulman, An introduction to ultrathin organic

films, (Academic Press, Boston, 1991). [4] I. Bâldea, Phys.Rev.B,85, 035442 (2012); J.M.

Beebe et al., ACS Nano, 2 (2008) 827. [5] M. Araidai, M. Tsukada, Phys.Rev.B, 81 (2010)

235114.

L. Patrone1, G. Delafosse1, B. Jousselme2, Y.-P. Lin2, Y. Ksari1, M. Abel1, M. Koudia1, J.-M. Themlin1

and S. Palacin2 [email protected]


Figure 1. STM I(V) of NaPh & 3T SAMs on Au(111). Bias is applied to the sample. Inset shows TVS graph: the bias VT at the minimum corresponds to the energy barrier and correlates with HOMO and LUMO onset measured by UPS and IPES respectively.

-6 -4 -2 0 2 4 6-3

-2

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/V²) HOMO

onset(UPS)

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+0.61 V

VT- =

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/V²)

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NaPh : 3T :-1.0 -0.5 0.0 0.5 1.0 1.5

-0.10

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Graphene Frontiers 3624 Market Street 5th Floor E, Philadelphia, Pennsylvania 19104, USA

Called “the miracle material of the 21st century,” graphene is a single atomic layer of carbon atoms, tightly bonded in a hexagonal lattice. It is a single atomic layer of graphite, with all interatomic bonds in a 2-dimensional plane. Despite its short history as an experimental system, graphene has already revealed exciting new physics and exceptional electronic, optical, mechanical, and chemical properties, which are appealing for a broad variety of applications in several fields. Potential applications include flexible, transparent electrodes, transistors, nanopore filters, impermeable coatings for corrosion and/or chemical protection, ultracapacitors, chemical sensors and biological sensors. Graphene Frontiers is developing a graphene-based biosensor platform for highly sensitive, rapid response, medical diagnostics. In this presentation, Mr. Patterson will discuss the work under way at Graphene Frontiers to develop and commercialize graphene electronics and sensor technology for medical diagnostics and related applications for heath care, fitness, security, and defense.

Michael D. Patterson

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1NUST “MISIS”, Leninsky prospect, 4, 119049 Moscow, Russia

2Helmholtz-Zentrum Berlin for Materials and Energy, Albert-Einstein-Str. 15, 12489

Berlin, Germany

Detonation-synthesized nanodiamonds (ND) are an effective type of reinforcing particle [1]. The size of the primary nanodiamond particles is 5 to 6 nm, but the particles can form agglomerates with dimensions of up to millimeter. Agglomeration is the primary barrier to the wide commercialization of nanodiamonds. For application to metal matrix composites, mechanical alloying allows effectively deagglomerating initial nanodiamond powders and producing non-agglomerated separate nanodiamond particles that are uniformly distributed in the metal matrix. For the present investigation, composites “aluminum + nanodiamonds” were used. Test specimens were prepared according to procedures described in paper [2]. The surface appearance of the produced composite granules of Al+10 vol% ND is shown in Figure 1. It is clearly observed that the agglomerates are completely shattered, and each individual nanodiamond particle is located in the matrix separately from the other particles. Identification of non-agglomerated nanoparticles in the metal matrix becomes extremely complicated, especially if their content is less than 10 vol%; this issue considerably impedes the development of new materials. Figure 2 presents proof that the commonly used and widespread X-ray diffraction (XRD) method fails to detect non-agglomerated diamond nanoparticles 5 to 6 nm in size if they are incorporated in a metal matrix: curve 1 shows results from mixture of initial agglomerates nanodiamonds with aluminum powder (nanodiamond peaks are visible), curve 2 shows results from mechanically alloyed composite granules with non-agglomerated nanodiamonds (nanodiamond peaks are practically absent).

Nuclear magnetic resonance is not available due to the electric conductivity of the material. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) can be applied only for the study of the composite granules before compaction, as their surfaces contain bare nanodiamond particles, and with a volume fraction of only 2 to 3%. It is necessary to note that in this case, the surface of the nanodiamonds can be partially covered by the matrix metal, which can cause error in the results because part of the signal from the nanoparticle can be lost, and there is no estimation of this error. After compaction of the granules, it is practically impossible to obtain a specimen surface with fully bare nanodiamond particles, as they have strong contact with the matrix and are always coated with a metal layer, although a slight one, which renders XPS and Raman spectroscopy methods unusable for the study of nanodiamonds in a metal matrix. The application of electron diffraction with a transmission electron microscope is complicated for these materials because the diamond peaks 111 and 202 are overlapped with aluminum peaks, and for a small volume fraction of nanodiamonds, the electron beam intensity is not sufficient for successful identification by diamond peak 311, due to the rather large diffraction angle. Taking into consideration the above, it was proposed to use synchrotron radiation for the identification of non-agglomerated nanodiamonds in a metal matrix. The produced granules were consolidated by pressurizing into cylindrical specimens 5 mm in diameter and 4 mm in height. Additionally, a specimen of initial nanodiamond powder was prepared for synchrotron tests. Before

Vladimir A. Popov1 Daniel Többens2, and Alexey Prosviryakov1


synchrotron investigation, a theoretical calculation of the expected X-ray diffraction pattern was made. Diffraction measurements were performed on the KMC-2 beamline of BESSY II (Berlin-Adlershof) in reflection geometry. A wavelength of 1.5406 Å (8048 eV) was used. A beam diameter of 0.2 mm and a Våntec 2000 area detector placed 543.6 mm from the sample were used. The detector was equipped with an anti-air scattering cone. The sample was placed at a constant angle of 45° to the beam. The diffraction angle range from 68-74° to 105°was measured. The detector was moved in 0.5° steps. As the range observed in each frame is 10°, the large degree of overlap results in the averaging-out of any potential systematic intensity fragments. The angular range was selected to observe the diamond 311 peak with a maximum separation from the surrounding peaks of the metal matrix. Depending on the volume fraction of nanodiamonds, the total measuring time was set between 1 and 6 h. Figure 3 shows the produced synchrotron radiation X-ray diffraction patterns for the specimens of the aluminum matrix composite with 10% and 5% volume fraction of nanodiamonds. The results correspond to the theoretical predictions calculated from the crystal structures using FullProf and the Scherrer formula. The position of diamond 311 peak matches with the theoretical models and

the peak position in the X-ray diffraction pattern of the pristine nanodiamonds. Acknowledgements The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under the EFEVE project, grant agreement 314582; the Russian Foundation for Basic Research (Project No.12-08-00210), and BESSY II (proposal 120812).

References

[1] V.A. Popov, B.B. Chernov, A.S. Prosviryakov, V.V. Cheverikin, I.I. Khodos, J.Biskupek, U. Kaiser, J. Alloys and Compounds, In Press, Corrected Proof, Available online 29 January 2014: http://dx.doi.org/10.1016/j.jallcom.2014.01.158.

[2] V. A. Popov, in: Nanocomposites: Synthesis, Characterization and Applications, Ed. Xiaoying Wang, Nova Science Publishers, Inc., NY, 2013, pp.369-401.

Figure 1. Surface appearance of Al + 10vol%ND composite granule (SEM image).

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http://dx.doi.org/10.1016/j.jallcom.2014.01.158


Figure 2. The X-ray diffraction patterns from Al+ 25%vol ND produced with use of Bruker D8 diffractometer: initial mixture of Al + ND powders (curve 1) and aluminum matrix composite after mechanical alloying during 4 hours (curve 2).

Figure 3. The X-ray diffraction patterns from the specimens of aluminum matrix composite with 10% (a) and 5% (b) volume fraction of nanodiamonds produced with use of synchrotron radiation.

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1Institut de Microelectrònica de Barcelona, IMB-CNM (CSIC), Campus UAB, 08193.

Barcelona, Spain 2Centro de Investigacion Biomedica en Red, Biomateriales y

Nanomedicina (CIBER-BBN), Spain 3IDIBAPS (Institute of Biomedical Research August Pi y Sunyer), Barcelona, Spain.

4ICREA (Institucio Catalana de Recerca y Estudis Avançats), Barcelona, Spain.

The fabrication of probes through microtechnologies has fostered critical advances in the understanding of brain neuronal networks in recent years, mainly by allowing multiple simultaneous recordings through silicon probes. Microelectrodes in neuroscience are needed for the efficient and selective stimulation or recording of different groups of neurons, as a basic tool to increase the knowledge about brain baseline functionality or even for diagnostics or treatment of neurodegenerative diseases. In this sense, we previously reported biosensors with optimal probe design for neural recording [1] and the integration of C-based material such as CNT[1b, 2] and graphene[1a, 1c, 3]. Recently we started to study and develop devices for neural recordings based entirely on graphene (Figure 1b). Taking advantage of the intrinsic properties [4] of graphene, such as the flexibility, transparency, biocompatibility, good electrode-electrolyte interface, and compatibility with standard microtechnologies, we hypothesized that graphene neural devices with enhanced performance with respect to the silicon-based ones could be developed. In this abstract, we present graphene based neural probes that can endow the neuroscience with an improved tool in contrast with the regular metallic sensors widely used by the neurophysiologists, which present many drawbacks. These disadvantages such as the electrode material degradation, the high laceration due to the rigidity in the mechanical device insertion, the foreign body response and the difficulties for obtaining and maintaining good recordings, arise mainly as a consequence of a lingering technological bottleneck that is the realization of a soft, minimal invasive, micron-sized

electrodes capable of recording neuronal activity without causing neither electrode nor tissue damage. Graphene has been envisaged to be a material with realistic chance to become the next disruptive material thanks to the combination in the same material of the intrinsic properties of graphene above mentioned. Motivated by this combination of properties, we fabricated a novel flexible neuronal microelectrode device based entirely on graphene technology with the capability of obtaining brain recordings and open of the double use as recording/stimulating electrodes plus compatibility with magnetic resonance imaging techniques. Specifically, the main objective with these devices is to detect signals with a functional signal-to-noise ratio. This noise can be divided into neural noise + thermal noise. This last one is associated to the electrode impedance, and the strategy in commonly used metallic electrodes to decrease this parameter and obtain good recordings is to increase the effective area by increasing the surface roughness. In the case of a graphene based device, the electrode is addressed to be purely capacitive, with no CPE behavior, eliminating by this way the thermal noise and so increasing the signal-to-noise ratio. The devices consist of conducting graphene material embedded in a flexible and biocompatible support such as COP of 40um thick, through transference from the grown CVD graphene, and then the graphene is protected by SU-8 polymer as

Elisabet Prats-Alfonso1,2, N. Tort-Colet3, M. Sánchez-Vives3,4, P. Godignon1,2, R. Villa1,2 and G. Gabriel1,2

[email protected]


a passivation layer. In this process standard microelectronic technology such as optical photolithography has been used to obtain a perfect defined area of the electrode from 500um to 10um diameter (Figure 1c). Once obtained the sensor it is encapsulated into a PCB to perform the final device. (Figure 1a). We currently explore the possibility of using the photolithography to perform devices with multiple electrodes. These devices have been characterized by impedance measurements and cyclic voltammetry to assess the viability for the recording experiments. The device has been tested in in vivo experiments to perform recordings of the neural activity and the results seem to be very promising in order to confirm that high quality brain recordings can be obtained with a satisfactory signal to noise ratio (Figure 1d). In contrast to the technology for flexible devices developed until know, here we present a promising and simple technology which uses a combination of micro and nano schemes for obtaining a nearly purely capacitive microelectrode entirely based on graphene with a defined area for neural applications.

References

[1] aE. Prats-Alfonso, P. Godignon, R. Villa, G. Gabriel, Handbook of Graphene Science, CRC press. Accepted book chapter 2014; bG. Gabriel, X. Illa, A. Guimera, B. Rebollo, J. Hernández-Ferrer, I. Martin-Fernandez, M. T. Martinez, P. Godignon, M. V. Sanchez-Vives, R. Villa, Physical and Chemical Properties of Carbon Nanotubes. 2013, ISBN 978-953-51-1002-6; cG. Gabriel, P. Godignon, E. Prats-Alfonso, M. V. Sanchez-Vives, R. Villa, Vol. Patente num: 201331895, 2013.

[2] aI. Martin-Fernandez, G. Gabriel, A. Guimerà, X. Palomer, R. Reig, M. V. Sanchez-Vives, R. Villa, P. Godignon, Microelectronic Engineering 2013, 112, 14-20; bG. Gabriel, R. Gómez, M. Bongard,

N. Benito, E. Fernández, R. Villa, Biosensors and Bioelectronics 2009, 24, 1942-1948.

[3] aP. Godignon, X. Jorda, M. Vellvehi, X. Perpina, V. Banu, D. Lopez, J. Barbero, P. Brosselard, S. Massetti, Industrial Electronics, IEEE Transactions on 2011, 58, 2582-2590; bJ. Chen, M. Badioli, P. Alonso-Gonzalez, S. Thongrattanasiri, F. Huth, J. Osmond, M. Spasenovic, A. Centeno, A. Pesquera, P. Godignon, A. Zurutuza Elorza, N. Camara, F. J. G. de Abajo, R. Hillenbrand, F. H. L. Koppens, Nature 2012, advance online publication; cB. Jouault, N. Camara, B. Jabakhanji, A. Caboni, C. Consejo, P. Godignon, D. K. Maude, J. Camassel, Applied Physics Letters 2012, 100.

[4] aA. K. Geim, K. S. Novoselov, Nat Mater 2007, 6, 183-191; bC. Schmidt, Nature 2012, 483, S37-S37

Figure 1. a) Neural probe entirely based on graphene, b) Graphene electrodes defined after photolithography, c) Encapsulated graphene neural probe d) Neural recordings made with the graphene probe prototype from the surface of the cerebral cortex of an anesthetized mouse. Recordings were obtained in the presence of GABAA receptor blockade.

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Universidad de Valencia. Instituto de Ciencia Molecular Edificios Institutos de Paterna. Catedrático José Beltrán Martínez nº 2 46980 Paterna - Spain

Spin-based electronics is one of the emerging branches in today´s nanotechnology and the most active area within nanomagnetism. So far spintronics has been based on conventional materials like inorganic metals and semiconductors. Still, an appealing possibility is that of using molecule-based materials, as components of new spintronic systems [1]. In particular, by taking advantage of a hybrid approach one can integrate molecular materials showing multifunctional properties into spintronic devices. In this talk we illustrate the use of this approach to fabricate multifunctional molecular devices combining light and spin-valve properties (i.e., Spin-OLEDs). So far only one report has been published which is based on the fabrication of an organic light emitting diode (OLED) with ferromagnetic electrodes [2]. Our approach is based on the use of a HyLED (Hybrid Light Emitting Diode) structure in which Fe or LSMO and Co are used as ferromagnetic electrode. This device works simultaneously as a spin valve and an electroluminescent device at low temperatures [3]. This new approach leads to a robust organic luminescent device in which light emission can be enhanced and modulated upon application of an external magnetic field.

References

[1] J. Camarero, E. Coronado, J. Mater. Chem. 2009, 19, 1678.

[2] T. Nguyen, E. Ehrenfreud, Z. Valy Vardeny, Science 2012, 337, 204.

[3] Opto-spintronic device and its fabrication method. E. Coronado Miralles; H. Prima Garcia, J.P. Prieto Ruiz. Spanish National Patent. Ref.

201300083, 2013, Spanish Office of Patents and Trademarks. Ministry of Industry, Energy and Tourism.

H. Prima–Garcia, E. Coronado and J. P. Prieto-Ruiz

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ICFO – The Institute of Photonic Sciences, Castelldefels (Barcelona), Spain

Ultrathin materials are becoming essential for the functionalization of optical surfaces, including glass and crystalline materials. In the talk we will show how ultrathin metals and graphene can be exploited to create competitive transparent electrodes and modulate the optical response. We will also provide examples of applications enabled by these materials and techniques, including efficient indium-free light emitting diodes and solar cells, light deflectors for 3-D displays, heads-up displays, self-cleaning or easy-to-clean screens, and super-wetting surfaces for biology.

Valerio Pruneri, M. Marchena, T.L. Chen, K. Kalavoor, D. Janner and D.S. Ghosh [email protected]

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ICFO-The Institute of Photonic Sciences, 08860 Castelldefels (Barcelona), Spain and ICREA-Institució Catalana de Recerca I Estudis Avançats, 08010 Barcelona, Spain

Recent years have seen a growing interest in using metal nanostructures to control temperature on the nanoscale. Under illumination at its plasmonic resonance, a metal nanoparticle features enhanced light absorption, turning it into an ideal nano-source of heat, remotely controllable using light. Such a powerful and flexible photothermal scheme sets the basis of the emerging and fast growing field of thermo-plasmonics. In this talk we first briefly present the physics of heat generation in metal nanoparticles [1]. We then focus on the experimental methods that have been developed to further understand and engineer plasmonic-assisted heating processes on the nanoscale [2-4]. Finally, we present a selection of applications from microscopy to biomedicine.

References

[1] Thermo-plasmonics: using metallic nanostructures as nano-sources of heat, G. Baffou, R. Quidant, Laser Photonics Rev. 7, 171-187 (2013)

[2] Mapping intracellular temperature using green fluorescent protein, J. S. Donner, S. A. Thompson, M. P. Kreuzer, G. Baffou, R. Quidant, Nano Lett. 12, 2107-2111 (2012)

[3] Deterministic temperature shaping using plasmonic nanoparticle assemblies G. Baffou, E. Bermudez Ureña, P. Berto, S. Monneret, R. Quidant, H. Rigneault Nanoscale 6, 8984-8989 (2014)

[4] Imaging of plasmonic heating in a living organism, J. S. Donner, S. A. Thompson, C. Alonso-Ortega, J. Morales, L. G. Rico, S. I. C. O. Santos, R. Quidant, ACSnano 7, 8666–8672 (2013)

Romain Quidant, J. S. Donner, R. Marty, J. Morales and G. Baffou [email protected]

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Universidad de Salamanca, Dpto. de Física Aplicada, Plaza de la Merced s/n, Salamanca, Spain

Graphene is an exciting material with electrical properties outperforming those of conventional semiconductors. For example, suspended monolayer graphene presents a much elevated intrinsic mobility at room temperature as compared to Si or III-V materials [1], which has been an important incentive for exploring the use of graphene in future electronic devices. In real samples, however, the presence of a supporting dielectric material may significantly degrade the electrical characteristics of graphene [2], although still a great advantage is obtained as compared to traditional semiconductors. In this work, we present an investigation of the temperature dependence of parameters such as the resistivity, saturation velocity or diffusion coefficient in suspended monolayer graphene and graphene on several types of substrates (e.g., h-BN, SiC, SiO2 and HfO2). The results have been obtained by means of an ensemble Monte Carlo (EMC) simulator. EMC simulators have previously shown their utility for an in-depth description of the electrical charge transport parameters in graphene [3-5]. The scattering mechanisms considered in the present work are intrinsic optical phonons, intervalley and intravalley acoustic phonons and surface polar phonon (remote phonon) scattering, or SPP. Impurities or defects are not taken into account in order to provide an adequate insight of the influence of the phonon scatterings related to the substrate type. The diffusion coefficient D is obtained by means of the analysis of the second central moment of the ensemble of particles diffusing across the material, and also from the Fourier analysis of velocity fluctuations, following the methodology described in [5]. The procedure involves the consideration of an excess carrier

population evolving according to a linearized Boltzmann transport equation, since the material is considered to be degenerate at low fields for the carrier concentration simulated (1012 cm-2); more details can be found in previous works [5,6]. The DC resistivity (obtained from the velocity-field curves at a small applied field equal to 10 V/cm) and the diffusion coefficient as a function of the temperature are shown in Figure 1. Excellent agreement with the resistivity results by other authors [3] (shown in the graph for the case of SiO2) is observed. As expected, at room temperature suspended graphene shows the largest diffusivity and lowest resistivity values, well beyond those obtained for supported samples. However, as the temperature is lowered, the differences tend to reduce. For example, suspended graphene and graphene on h-BN or SiC show similar D and resistivity values for temperatures below 175K, and graphene on SiO2 gets close also for T < 100K (and so do the mobility values, not shown in the graphs), which is strongly related to the behaviour of SPP interactions, as it will be discussed later. The anisotropic nature of SPP interactions yields larger saturation velocities as compared to the suspended case at 300 K [6], which are maintained also for lower temperatures, with the only exception of HfO2 (Figure 2(a)) for which the remote phonon activity is extraordinarily large due to the small phonon energies in that case. Negative differential conductivity (NDC) was clearly evidenced in all cases, with the exception of graphene on HfO2, for which only a small NDC was obtained at very high fields. NDC becomes more evident at low temperatures (Figure 2(b)). It is important also to notice the augmentation of the scattering time at low temperatures, particularly for graphene on SiO2

Raúl Rengel, Elena Pascual and María J. Martín [email protected]


(Figure 3(a)). In general, there is an important reduction of the SPP activity at low temperatures, as evidenced in Figure 3(b), which explains that, in an ideal framework absent of impurities and defects, for temperatures in the range of 100K and below graphene on h-BN, SiC or SiO2 have comparable electrical characteristics to those of suspended graphene. This work has been funded by research project TEC2013-42622-R from the Ministerio de Economía y Competitividad.

References

[1] K. Bolotin et al., Solid State Communications, 146 (2008) 351

[2] Z.-Y. Ong and M. Fischetti, Physical Review B, 88 (2013) 045405

[3] X. Li et al., Applied Physics Letters, 97 (2010) 232105

[4] N. Sule, et al., Journal of Computational Electronics 12 (2013) 563

[5] R. Rengel and M. J. Martin, Journal of Applied Physics, 114 (2013) 143702

[6] R. Rengel, E. Pascual and M. J. Martin, Applied Physics Letters, 104 (2014) 233107

Figure 1. DC resistivity (a) and diffusion coefficient (b) as a function of the temperature for suspended graphene and graphene on different types of substrates. The carrier concentration is 10

12 cm

-2. The white stars in (a)

show values for SiO2 from reference [3].

Figure 2. Maximum drift velocity for suspended graphene and graphene on different types of substrates (a). Velocity-field curves for suspended graphene and graphene on h-BN (b).

Figure 3. Scattering time at an applied field equal to 10 V/cm (a) and percentage of SPP scattering mechanisms over the total number of scatterings in graphene on h-BN, SiC, SiO2 and HfO2 (b).

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1Small biosystems lab, Departament de Física Fonamental, Facultat de Física, Universitat

de Barcelona, Diagonal 647, 08028 Barcelona (Spain) 2

CIBER-BBN, Centre of Bioengineering, Biomaterials and Nanomedicine, ISCIII, Madrid (Spain)

The recent advent of micromanipulation tools allow scientists to monitor and follow molecular processes one molecule at a time. By exerting tiny forces (in the range of piconewtons) on individual molecules, single molecule experiments allow scientists to measure energies as small as 1kcal/mol opening new domains of application ranging from the study of antigen-antibody interactions in the humoral immune system [1] to the characterization of the different binding modes of anticancer drugs interacting with DNA. For the latter three mechanisms of drug-DNA action have been identified: DNA elongation by unwinding (e.g. intercalation), DNA bending (e.g. by major and minor grove binding) and DNA condensation and collapse (e.g. induced by electrostatic effects and aggregate formation). The elucidation of the different mechanisms of action of anticancer drugs on essential molecules such as DNA is key to fully understand their direct and indirect effects when supplied to the patient. In this talk I will review some of the most important results obtained in my group on this exciting field. I will start by briefly reviewing some of the results obtained in my lab in the study of Kahalalide-F (KF), an anticancer hydrophobic peptide that reached clinical phase trial II and contains a single positive charge that confers strong aggregative properties with DNA [2]. Our results suggest that in an in vivo context, the enhanced electrostatic interaction of KF due to its aggregation might mediate the binding to other polyanions such as phospholipids in the plasma membrane inducing the observed formation of pores and cell necrosis [3]. Next, I will describe results on a DNA bis-intercalator peptide Thiocoraline synthesized by Pharmamar (Zeltia Group) that reached clinical phase trial I. Thiocoraline elongates DNA by approximately 50%

and shows an extremely slow off-rate (hours) that increases with force [4]. We have also determined that Thiocoraline binds DNA in a specific and non-specific manner via an intermediate state, with a preference for clamping CG dinucleotide motifs. Finally, single molecule methods are not only a powerful tool to dissect mechanisms of action of complex anticancer drugs, they can also be used to discriminate specific binding sites on DNA providing and efficient and accurate way to footprinting. Results for other peptide and protein binders will be shown.

References

[1] A. Alemany, N. Sanvicens, S. De Lorenzo, P. Marco and F. Ritort, Bond Elasticity Controls Molecular Recognition Specificity in Antibody-Antigen Binding, Nano Letters 13 (2013) 5197-5202.

[2] J. Camunas-Soler, S. Frutos, C. V. Bizarro, S. de Lorenzo, M. E. Fuentes-Perez, R. Ramsch, S. Vilchez, C. Solans, F. Moreno-Herrero, F. Albericio, R. Eritja, E. Giralt, S. B. Dev, and F. Ritort, Electrostatic Binding and Hydrophobic Collapse of Peptide-Nucleic Acid Aggregates Quantified Using Force Spectroscopy, ACS Nano, 7 (2013) 5102-5113.

[3] J Molina-Guijarro, A. Macías, C. García, E. Munoz, L. García-Fernández, M. David, L. Nunez, J. Martínez-Leal, V. Moneo, C. Cuevas, Irvalec Inserts into the Plasma Membrane Causing Rapid Loss of Integrity and Necrotic Cell Death in Tumor Cells. PLoS One, 6 (2011) e19042.

[4] J Camunas-Soler, M. Manosas, S. Frutos, J. Tulla-Puche, F. Albericio and F Ritort, Forcespectroscopy reveals extremely slow force-dependent kinetics of Thiocoraline and structural insights on DNA bis-intercalation, submitted

Felix Ritort1,2 [email protected]

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Catalan Institute of Nanoscience and Nanotechnology ICN2 & ICREA

Campus de la UAB, Edifici ICN2 08193 Bellaterra (Barcelona) Spain One will present the multiscale computational platform of ICN2 and outline the various topics of concern within the Severo-Ochoa program, including vibrational properties of graphene and two-dimensional materials and thermal transport, and spin-orbit coupling effects and spin dynamics in topological insulators.

Stephan Roche


1Dpto. de Física Teórica de la Materia Condensada and IFIMAC, UAM, Madrid, Spain.

2Centro de Astrobiología INTA-CSIC, Madrid, Spain.

3Instituto de Ciencias de Materiales de Madrid, CSIC, Madrid, Spain.

Understanding the connection of graphene with metal surfaces is a necessary step for developing atomically-precise graphene-based technology. Previous studies have shown that highly perfect sheets of graphene can be obtained by epitaxial growth on metal surfaces, and for some transition elements, like Cu or Pt, the interaction is very weak and many characteristic properties of graphene are preserved [1,2]. In this work [3], we show the structure of graphene grown on Pt close to the steps where the flakes start to nucleate. To this end, we combine scanning tunneling microscopy at (STM) experiments with density functional theory calculations (DFT) and non-equilibrium Green's functions (NEGF) methods to unveil the atomic structure of a border-like edge between a Pt(111) step and a graphene zigzag edge. RT-STM experiments have succeeded in mapping the structure of a graphene flake on a Pt step edge showing atomic resolution not only on both the graphene and the metal but also on the boundary (see Fig. 1). By combining the experiments with our ab initio simulations, we have been able to understand the competition between the interaction of graphene with the step and with the Pt surface that controls the structure and chirality of the flake edge and the observed Moiré structures. We can conclude then that the tendency to form passivated zigzag graphene terminations plays a relevant role in the formation and orientation of the stable Moiré patterns. The unsaturated C atoms strongly interact with the Pt step, preserving a zigzag structure quite close to the ideal configuration. However, on the

other side, Pt edge atoms experience a 3-fold reconstruction that stabilizes the structure. Our combined approach also reveals the interesting electronic properties of this nanoscopic system including, as stated by the simulations, the preservation of the G-edge state shifted to energies at about +0.8 eV above Fermi level, highly localized in one of the graphene sublattices and confined to the G-Pt interface. This state spreads out inside the first Pt row resulting in a high quality G-metal electric contact that could be relevant for designing future atomically precise graphene metal leads [4]. No signs of local magnetic moments were found.

References

[1] P. Sutter et al., PRB, 80 (2009) 245411. [2] Martínez-Galera et al., Nano Lett., 11 (2011)

3576. [3] P. Merino, L. Rodrigo et al., ACS Nano, 8 (4)

(2014) 3590–3596. [4] L. Wang, et al., Muller, D., Science 342 (6158)

(2013) 614-617.

Figure 1. A) Experimental RT-STM image of a graphene flake on a Pt(111) step edge. B) Atomic structure of graphene zigzag edge on a Pt step calculated by a DFT method based on VASP. C) STM image with atomic resolution on the metal, the graphene and the boundary compared with the atomic structure calculated with DFT. D) Simulated STM profiles at

constant height (2.75 Å) for different bias voltages.

L. Rodrigo1*, P. Merino2, A. L. Pinardi3, J. Méndez3, M. F. López3, P. Pou1, J. A. Martín-Gago2,3, R. Pérez1 [email protected]

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Infineon Technologies AG, 93049 Regensburg, Germany

Graphene is a novel material which has attracted a lot of attention during the last years. Since the discovery of its electrical properties in 2004 the expectations on its possible applications have increased dramatically. The apparent hype makes it difficult for industry to realistically assess the technological implementation potential of graphene, so it has to be broken down into its components (Fig. 1). Different indicators for this assessment, like public attention, expert opinions or patent analysis, yield inconsistent conclusions, so there is no simple answer for potential graphene users. Against this background possible application drivers and fundamental obstacles from the semiconductor industry point of view, as graphene quality, CMOS compatibility and process integration issues, are discussed. In this context a consistent graphene supply quality turned out to be one of the most important requirements.

Figure 1. Breakdown of the hype cycle into its components.

Günther Ruhl


ICN2 - Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona), Spain CSIC - Consejo Superior de Investigaciones Cientificas, ICN2 Building , Campus UAB, 08193 Bellaterra (Barcelona), Spain.

Catechols are found in nature taking part in a remarkably broad scope of biochemical processes and functions. Though not exclusively, such versatility may be traced back to several properties uniquely found together in the o-dihydroxyaryl chemical function; namely, its ability to establish reversible equilibria at moderate redox potentials and pHs and to irreversibly cross-link through complex oxidation mechanisms; its excellent chelating properties, greatly exemplified by, but by no means exclusive, to the binding of Fe3+; and the diverse modes of interaction of the vicinal hydroxyl groups with all kinds of surfaces of remarkably different chemical and physical nature. Thanks to this diversity, catechols can be found either as simple molecular systems, forming part of supramolacular structures, coordinated to different metal ions or as macromolecules mostly arising from polymerization mechanisms through covalent bonds. Such versatility has allowed catechols to participate in several natural processes and functions that range from the adhesive properties of marine organisms to the storage of some transition metal ions. According to such astonishing range of functionalities, catechol-based systems have been subject in recent years to intense research, aimed at mimicking these natural systems in order to develop new functional materials and coatings. With this aim in our group we have fabricated different nanostructures ranging from nanoparticles to functional coatings with applications on very different fields, from sensors, to green nanoreactors or theranostic applications, which will be briefly revised in this presentation.

References

[1] J. Sedó, J. Saiz-Poseu, F. Busqué, D.Ruiz-Molina. Adv. Mater. 2013, 25, 653–701

[2] J. Saiz-Poseu, J.Sedó, B. García, C. Benaiges, T. Parella, R. Alibés, J. Hernando, F. Busqué, D. Ruiz-Molina. Adv. Mater. 2013, 25, 2066–2070

[3] M. Guardingo, E. Bellido, R. Miralles-Llumà, J. Faraudo, J. Sedó, S. Tatay, A. Verdaguer, F. Busqué, D. Ruiz-Molina Small, 2014, 10, 1594–1602.

[4] F. Novio, J. Lorenzo, F. Nador, K. Wnuk, D. Ruiz-Molina Chem. Eur. J. 2014, DOI: 10.1002/chem.201403441.

[5] B. García, J. Saiz-Poseu, R. Gras-Charles, J. Hernando, R. Alibés, F. Novio, J. Sedó, F. Busqué, D. Ruiz-Molina ACS Appl. Mater. Interfaces 2014, dx.doi.org/10.1021/am503733dPerea et al., Nano Lett. 11 (2011) 3117

Daniel Ruiz-Molina [email protected]

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Sungkyunkwan Univ. & Center for Integrated Nanostructure Physics (IBS), South Korea

In this presentation the use of electron irradiation to grow 1D and 2D nanostructures will be presented. The fabrication of these nanostructures is accomplished by using the electrons used to image specimens in a transmission electron microscope. No specialized holders or systems are required making the technique relatively cheep and easy. As examples of the technique I will demonstrate of electron irradiation can be used to form 1D coaxial B/BOx nanowires and BOx nanotubes. In addition, I will show how 1 atom thick Fe membranes can be formed and also the catalytic activity of a single atom for the growth of or etching of graphene can be accomplished. In addition the in-situ fabrication and structuring of graphene will be presented. The technique provides unprecedented insight in to nanostructure formation at the atomic scale.

Mark H. Rummeli

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1Institut de Ciència de Materials de Barcelona (ICMAB–CSIC) Campus de Bellterra,

08193 Bellaterra, Barcelona, Spain 2Departament d’Enginyeria Electrònica, Universitat Autònoma de Barcelona,

08193 Bellaterra, Barcelona, Spain 3Dipartimento di Fisica, Università di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Ca), Italy

Semiconducting nanowires (NWs) have attracted a growing interest in recent years and are recognized as important building blocks for emerging applications in nanoelectronics [1-3]. The understanding of thermal transport has lately acquired a great importance as well, because NWs have been proposed to be a pathway for the engineering of efficient thermoelectric materials. Here we study thermal transport in SiGe nanowires across a Si/Ge axial interface by means of nonequilibrium molecular dynamics simulations. We calculate the interface thermal resistance (ITR) of realistic models of axial SiGe heterojunctions, whose morphology depends strongly on the different experimental conditions [4-7]. We also investigate if these asymmetric junctions can yield thermal resistances that depend on the applied thermal gradient, i.e. thermal rectification. We find that diffuse interfaces result in larger ITR, while sharp junctions yield a small, but non-negligible thermal rectification, favoring heat transport from Si to Ge. These results can be tracked back to the different temperature dependence of the thermal conductivity of Si and Ge NWs, thus indicating that rectification derives from properties of the pristine NWs and can be tuned by the morphology of the interface. Curvature of the flat interface provides an additional modulation on both the ITR and the thermal rectification. These results shade a light on the atomic scale nature of the ITR and the observed thermal rectification is promising for the engineering of nanoscale phononic devices.

References

[6] D. K. Ferry, Science 319 (2008) 579 [7] R. Rurali, Rev. Mod. Phys. 82 (2010) 427 [8] M. Amato, M. Palummo, R. Rurali, and S.

Ossicini, Chem. Rev. 114 (2014) 1371 [9] Clark et al., Nano Lett. 8 (2008) 1246 [10] Wen et al., Science 326 (2009) 1247 [11] Perea et al., Nano Lett. 11 (2011) 3117 [12] Geaney et al., Nano Lett. 13 (2013) 1675

Figure 1. SiGe axial heterojunctions studied in this work. (a) atomically sharp, flat interface; (b,c) diffuse interface where the chemical composition switches from Si to Ge within a region of 5 and 15 nm; (d) curved interface. Light yellow spheres and dark blue spheres represent Si and Ge atoms, respectively. A ball-stick model is used for Ge in panel (d) to show the hemispherical shape of the interface.

Riccardo Rurali1, Xavier Cartoixà2, and Luciano Colombo3 [email protected]


Figure 2. Heat rectification r as a function of |ΔT| in a 20 nm SiGe NW with an abrupt (empty black circles) and a diffuse interface, δl = 5 nm (empty red diamonds) and in a 40 nm SiGe NW with an abrupt interface (filled black circles). Notice that in the case of diffuse junctions, due to random nature of the alloy region, one should in principle average the results over several different configurations.

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Physics, Centre for Graphene Science, University of Exeter, StockerRoad 6, EX4 4QL Exeter, UK

The emerging class of atomically thin semiconducting materials formed by transition metal Dichalogenides (TMDCs) is showing a plethora of complementary properties to those of graphene that are of interest to fundamental and applied research. More specifically, WS2 has a direct band gap of 2 eV in single layer form [1-2] and has already shown great promise as a flexible transistor with field effect mobilities comparable to the best liquid crystals and on/off ratio of the current exceeding 106 [3]. Understanding the limiting factors of the electrical properties of TMDCs is an open quest and a stepping stone for accessing novel physics in these systems. Here I will present the first study of the intrinsic electrical properties of WS2 transistors fabricated with two different dielectric environments WS2 on SiO2 and WS2 on h-BN/SiO2, respectively. A comparative analysis of the electrical characteristics of multiple transistors fabricated from natural and synthetic WS2 with various thicknesses from single- up to four-layers (identified by Atomic Force Microscopy and Raman spectroscopy) and over a wide temperature range from 300K down to 4.2 K shows that disorder intrinsic to WS2 is currently the limiting factor of the electrical properties of this material [4]. Another emerging TMDCs is MoS2, with a band gap of 1.9 eV in single layer form. Also in this case, I will elucidate the limiting factors of the electrical properties presenting a comparative study of the electrical properties measured in transistor geometries with different dielectric environments, such as supported MoS2 on SiO2 and suspended MoS2 see Figure 1a. Also in the case of MoS2 disorder intrinsic to the crystal is the limiting factor of the electrical properties, and I will show this by conducting a detailed analysis of the

temperature dependence of the transistor characteristics, that is source-drain current (I) versus back gate voltage (Vbg) as shown in Figure 1b. These results shed light on the role played by extrinsic factors such as charge traps in the oxide dielectric thought to be the cause for the commonly observed small values of charge carrier mobility in transition metal dichalcogenides.

References

[1] Mak, K.F., Lee, C., Hone, J., Shan, J. and Heinz, T.F. Phys. Rev. Lett. 105, (2010) 136805.

[2] Gutirrez, H.R., et al. Nano Lett. 13, (2013) 3447. [3] McCulloch, I., et al. 5, (2006) 328. [4] Withers, I., Bointont, T.H., Hudson, D.C.,

Craciun, M.F. and Russo, S. Scientific Reports 4, (2014) 4967.

Figure 1. a) False coloured scanning electron micrograph of a suspended single layer MoS2 (highlighted in green) transistor with gold contacts (highlighted in yellow). The scale bar corresponds to 1 μm. b) Graph of the characteristics of this transistor for different temperatures as indicating in the legend.

S. Russo [email protected]

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LCC, CNRS, and Universite de Toulouse (UPS, INP), 205 route de Narbonne, F-31077 Toulouse, France

A number of pseudo-octahedral 3d4-3d7 transition metal complexes have been reported to display a molecular bistability of their high-spin (HS) and low-spin (LS) electron configurations, which can be reversibly interconverted under external stimuli, such as temperature, pressure, magnetic field, or light irradiation. This spin crossover (SCO) phenomenon is accompanied by a spectacular change of magnetic, optical, dielectric, and mechanical properties. [1] In the past years, the SCO field has found a strong renewed interest mainly inspired by the emergence of nanosized SCO materials such as coordination nanoparticles and nanopatterned thin films2. The lowest size limit at which these cooperative effects are maintained turns into one of the key fundamental questions in this field. Beside the intriguing size-related properties, synthesizing thin films and other nanoscale assemblies of SCO complexes also represents a key step toward their technological applications in photonic and electronic devices [2]. Conventional macroscopic techniques as magnetic susceptibility and heat capacity measurements, X-ray diffraction, and Mossbauer, vibrational, and electronic spectroscopies has become very limited for the investigation of SCO at the nanometer scale, and the development of new experimental approaches becomes indispensible. In this presentation, we describe different approaches for the elaboration of thin films of SCO materials and we show that the use of the surface plasmon resonance (SPR, see figure below) spectroscopy can be a very powerful tool to detect the variation on the refractive index that

accompanies the SCO phenomenon at the nanometric scale. [3-4].

References

[1] Gutlich, P., Goodwin, H., Eds. Topics in Current Chemistry, Vols. 233-235; 2004.

[2] Bousseksou, A.; Molnar, G.; Salmon, L.; Nicolazzi, W. Chem. Soc. Rev. 2011, 40, 3313–3335.

[3] Felix G.; Abdul-Kader K.; Mahfoud, T.; Gural’skiy, I.; Nicolazzi, W.; Salmon, L.; Molnar G.; Bousseksou, A.; JACS, 2011, 133, 15342.

[4] Abdul-Kader, K.; Lopes, M. ; Bartual-Murgui, C. ; Kraieva, O. ; Hernandez, E. M.; Salmon, L. ; Nicolazzi, W. ; Carcenac, F. ; Thibault, C. ; Molnar G. ; Bousseksou A. Nanoscale, 2013, 5, 5288.

Jose Sanchez Costa, Sylvain Rat, Gautier Felix, Khaldoun Abdul-Kader, William Nicolazzi, Lionel Salmon, Gabor Molnar and Azzedine Bousseksou [email protected]

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Departamento de Química Física, Universidad de Salamanca, Plaza de los Caídos s/n, 37008 Salamanca, Spain

Graphene oxide (GO) has recently become an attractive building block for fabricating graphene-based functional materials, this is because it possesses unique set of properties arising from oxygen functional groups that are introduced during chemical oxidation of the starting materials. Large-area GO thin-film offers a route towards GO-based thin-film electronics and optoelectronics. However, several issues can be explored to modulate the properties of these films. One important issue is to investigate the role of the chemical composition of the graphene oxide samples on the properties of thin films. This information is critical to modulate the structure of graphene oxide films according to the properties needed for different technological applications. With this objective in mind, we analyze the effect of the chemical structure on the graphene oxide films deposited onto Si/SiO2. Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) methodologies were chosen. These methods were selected because they allow a great control of the packing density and since each technique provides different contact between the solid support and the molecules adsorbed at the interface we expect that allow us to understand the role of the chemical structure on the properties of GO thin films. To synthesize graphene oxide of different functionalization, two starting materials, graphite and GANF® nanofibers [1], were used. The oxidation procedure was a slight modification of Hummers method reported previously by our group [2,3]. The samples thus obtained were subsequently purified by alkaline washing and its chemical composition was analyzed by XPS. GO samples were also characterized by zeta potential and Dynamic Light Scattering measurements. Results show that the percentage of COOH groups attached to graphene oxide obtained from

nanofibers is twice the value corresponding to GO synthesized by graphite oxidation, while the percentage of hydroxyl or epoxy groups, localized at the basal plane for the former sample is higher. Moreover, the percentage of Csp2 is similar for the non-purified samples. The purification procedure by alkaline washing increases the Csp2/sp3 ratio and renders samples of Csp2 percentage similar to that reached by chemical reduction of graphene oxide. Small differences between the chemical compositions of purified samples synthesized from the two starting materials were observed. The electric charge and the size of sheets of graphene oxide synthesized by oxidation of graphite are higher than those corresponding to sheets obtained from GANF®. Comparison between the zeta potential values of purified and non-purified sheets allows concluding that the electric charge is always higher for purified samples than for non-purified ones. This fact is compatible with the elimination of highly oxidized organic fragments, Oxidation Debris (OD), originated by the chemical oxidation. After samples characterization, the next step was to study the effect of the GO structure on the morphology and coverage of thin films obtained by the Langmuir-Blodgett and Langmuir-Schaefer methodologies. The morphology of films was analyzed by SEM and the coverage and the size of flakes deposited by the different methods were determined by ImageJ 1.46 software. Results show that the LB methodology renders higher coverage than the LS one. Moreover, the solid coverage reached by LB is almost independent of the C-O percentage while it increases with the percentage of C-O groups for films prepared by the LS methodology. Differences can be attributed to the distinct solid orientation in the two deposition techniques. Purified samples render lower coverage

R. Sánchez-Hidalgo, D. López-Díaz and M.M. Velázquez [email protected]


than the non-purified ones. The OD elimination is responsible of this behavior. The flake size determined by DLS agrees very well with the value obtained from the analysis of SEM images. Acknowledgements We thank European Regional Development Fund, ERDF, Ministerio de Educación y Ciencia (MAT 2010-19727) and Ministerio de Economía y Competitividad (IPT-2012-0429-420000) from the financial support. We thank Dr. J.L. García Fierro (ICP, CSIC, Madrid) for the XPS measurements.

References

[1] http://www.granphnanotech.com/ [2] B. Martín-García, M. M. Velázquez et al,

ChemPhysChem, 13 (2012) 3682. [3] D. López-Díaz, M.M. Velázquez, et al,

ChemPhysChem, 14 (2013) 4002.

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Centro de Física de Materiales UPV/EHU-CSIC, Paseo Manuel de Lardizabal 5, 20018 San Sebastián, Spain

We have recently used time-dependent density functional theory (TDDFT) to study a number of problems related to the dynamics of electrons and the optical response of solids and nanostructures. Our simulations are based on either real-time time-dependent SIESTA simulations or linear response calculations on the frequency domain. To perform real-time time-dependent simulations we have developed a new version of the SIESTA code [1], a first-principles code that uses a linear combination of atomic orbitals as a basis set, that allows performing coupled electron-nuclear dynamics within the Ehrenfest approximation. With this program we have studied the problem of the electronic energy loss of ions, like protons, antiprotons and He, in metals and insulators [2,3,4]. Although radiation damage processes are of extraordinary fundamental and technological importance, ab initio simulations of these effects in solids are still very scarce to date. Most simulations for solids and condensed systems are based on semi-empirical approaches, in which the effect of electronic stopping is frequently incorporated in simulations through an ion and target dependent friction coefficient. However, it has been recently observed that there are significant deviations from linearity at low velocities in insulators and noble metals, both showing different kinds of threshold effects. Our simulations using time-evolving TD-DFT could reproduce the anomalies in the stopping power observed experimentally for projectile velocities below 0.3 a.u., for insulators and noble metals [2,3]. We could also study the influence of the electron excitations on the effective internuclear forces when an Al target is bombarded with protons [3]. Understanding of such effects demands an explicit treatment of the electronic stopping in the presence of the actual atoms and actual electronic structure of the host system.

We have also used linear response TD-LDA simulations to study the optical properties of large nanostructures. These simulations are performed using an efficient method developed by P. Koval et al. [5] that uses SIESTA ground-state simulations as a starting point. With an improved version of this method it has been possible to study the optical response of graphene quantum-dots with up to 1000 atoms (see Figure 1) [6,7], as well as to study the plasmonic resonances of large metal clusters.

References

[1] J. M Soler, E. Artacho, J. D. Gale, A. García, J. Junquera, P. Ordejón and D. Sánchez-Portal, J. Phys.: Condens. Matter 14 (2002) 2745.

[2] J. M. Pruneda, D. Sánchez-Portal, A. Arnau, J. I. Juaristi, and Emilio Artacho Phys. Rev. Lett. 99 (2007) 235501.

[3] M. A. Zeb, J. Kohanoff, D. Sánchez-Portal, A. Arnau, I. Juaristi and E. Artacho, Phys. Rev. Lett. 108 (2012) 225504.

[4] A. A. Correa, J. Kohanoff, E. Artacho, D. Sánchez-Portal and A. Caro, Phys. Rev. Lett. 108 (2012).

[5] P. Koval, D. Foerster and O. Coulaud, J. Chem. Theo. Comp. 6, 2654 (2010).

[6] A. Manjavacas, F. Marchesin, S. Thongrattanasiri, P. Koval, P. Nordlander, D. Sánchez-Portal and F. J. García de Abajo, ACS Nano 7, 3635 (2013).

[7] F. Marchesin, P. Koval, D. Foerster and D. Sánchez-Portal (submitted 2014).

Daniel Sánchez-Portal [email protected]


Figure 1. a) Isosurface of the induced density for a proton traversing an Al sample at v=0.5 a.u. (image by Alfredo Correa) [4]; b) Scaling of the main π-plasmon resonance for un-doped graphene quantum-dots of different shapes and sizes [7].

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1CIC nanoGUNE, 20018 Donostia-San Sebastian, Spain

2Department Electrical and Computer Engineering and The Beckman Institute for

Advanced Science and Technology, University of Illinois, Urbana, Illinois 61801,USA 3CIC nanoGUNE and UPV/EHU, 20018 Donostia – San Sebastian, Spain

4IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain

We demonstrate a novel holographic method, termed synthetic optical holography (SOH) [1], for fast phase imaging in scanning near-field optical microscopy (s-SNOM). The holographic principle of phase detection enables fast near-field imaging with unprecedented speed, allowing for the acquisition of standard sized (256 x 256 pixel) near-field images in 26 seconds and megapixel images in less than 15 minutes. At the same time SOH offers technical simplicity as only a linearly moving reference mirror needs to be added to an existing near-field microscope setup.

We apply the fast phase imaging capabilities of SOH to nanoscale, noninvasive and rapid screening of grain boundaries in CVD-grown graphene, by recording 2.3 megapixel near-field images in only 13 minutes. The images (Fig. 1) reveal a network of grain boundaries [1], owing to the large reflection of tip-induced graphene plasmons [2,3] at the grain boundaries [4]. Study of the near-field phase contrast directly reveals the propagating nature of graphene plasmons, which might benefit the quantitative analysis of plasmon interference phenomena. Noninvasive and rapid near-field

mapping of graphene grain boundaries and defects could benefit the optimization of growth process and quality control.

References

[1] Schnell, M. et al., Nature Commun. 5, 3499 (2014)

[2] Chen, J. et al. Nature 487, 77 (2012) [3] Fei, Z. et al. Nature 487, 82 (2012). [4] Fei, Z. et al., Nature Nanotech. 8, 821 (2013)

Figure 1. Reconstruction of near-field amplitude and phase images (right) of a graphene grain boundary from a synthetic near-field hologram (left, 256 x 256 pixel), which was recorded in only 26 s.

M. Schnell1, P. S. Carney2 and R. Hillenbrand3,4 [email protected]

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CVD Equipment Corporation, 355 S. Technology Drive, Central Islip, New York 11722, USA

Process development for CVD graphene is typically being done on Cu or Ni substrates in a CVD tube furnace system. Traditionally such systems allow only limited production volume as a result of the size constraints of the substrates that can fit inside a given process chamber. Therefore, in order to commercialize applications enabled by CVD graphene films, new scale up solutions need to be developed that are commercially viable. Roll to roll CVD process systems have been previously proposed and perused by start-up companies as preferred candidates for volume production of CVD graphene material on a Cu foil substrate roll. In this presentation, we will compare the advantages and disadvantages of new patent [1] pending batch processing systems to roll to roll CVD processing systems for volume production of CVD graphene on Cu foils. In particular, we will show that with this novel batch method, a wide variety of CVD graphene production processes can be transitioned to volume production in a more straightforward way. The same hardware platform that enables the processing of multiple Cu substrates in parallel or the processing of a full Cu roll inside a CVD tube furnace can also be used to scale up production for a wide range of 1D and 2D nanomaterials [2]. Our EasyGraphene™ and EasyTube® systems (see Fig. 1) comes with different options. Fig. 2 shows the scale up of uniform growth of mm-sized CVD graphene islands on a 300 mm square Cu foil substrate. Fig. 3 shows our “Archimedes Spiral” concept used to increase production volume inside a tube furnace and Fig. 4 shows the estimated roll length capacity as a function of process tube diameters.

References

[1] Scalable 2D-FILM CVD Synthesis, patent pending. [2] Scalable CVD Film and Nanomaterials Synthesis,

patent pending

Figure 1. EasyGrapheneTM

Process Solutions.

Figure 2. mm-sized graphene islands

Figure 3. “Archimedes Spiral” for processing substrates in a batch CVD system

Figure 4. Volume production potential for Cu foil roll with our patent pending batch processing solution

Karlheinz Strobl, Mathieu Monville, Riju Singhal, Samuel Wright, and Leonard Rosenbaum [email protected]

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Universität Regensburg Institute for Experimental and Applied Physics, University of Regensburg 93040 Regensburg - Germany

Ultraclean carbon nanotubes form quantum dots of well-defined atomic structure at low temperatures. Transport spectroscopy of ground and excited states as a function of electron numbers in a parallel magnetic field results in detailed information about the band structures, in particular on spin-orbit and KK'-mixing effects. This information is exploited in the analysis of the SU(4) Kondo effect [1] occurring at larger electron numbers, where the devices become more transmissive. The slightly broken fourfold degeneracy in our device gives rise to satellites of the Kondo peak that shift in a characteristic way in perpendicular and parallel magnetic field. Our observations can be understood in terms of the discrete symmetries of the carbon nanotubes, and are well reproduced by state of the art theoretical modeling [2].

References

[1] P. Jarillo-Herrero et al., Nature 434, 484 (2005). [2] S. Smirnov and M. Grifoni, Phys. Rev. B 87,

121302 (2013).

Christoph Strunk

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1Unidad de Investigación de Materiales Moleculares, Instituto de Ciencia Molecular,

46980 Paterna, Spain 2Unité Mixte de Physique CNRS/Thales associée à l’Université Paris-Sud, 91767 Palaiseau,

France

Molecular spintronics, the combination of chemistry potential to the spin degree of freedom provided by spintronics, is considered to be more than an alternative to conventional spintronics with inorganic materials. Unconventional properties and strong potentialities offered by the flexibility, chemical engineering and low production costs of molecules, add to the opportunity that spin lifetime could be enhanced by several orders of magnitude compared with inorganic materials. Very recently it has been highlighted that the metal/molecule hybridization could strongly influence interfacial spin properties going from spin polarization enhancement to its sign control in spintronics devices [1]. In this scenario, while scarcely studied [2] [3], self-assembled monolayers (SAMs) seem to be the perfect toy barriers to further test these tailoring properties in molecular magnetic tunnel junctions (MTJs) since they are composed by a head, a body and an anchoring group that can be independently tuned thus allowing an easy engineering of the barrier. We present nanodevices based on alkyl phosphonic acids SAMs used as tunnel barrier grafted on the half-metallic manganite (La,Sr)MnO3 (LSMO) [4]. The prepared LSMO/SAMs/Co magnetic tunnel junctions present an area of only few 10 nm2 to allow the study of the local properties of the system and to avoid defects inside the barrier. We will present the atypical bias voltage dependence of tunnel magnetoresistance (TMR) highlighting the peculiar role of molecules in the spin dependent tunnelling transport (Figure 1a) [5].

We will also show the influence of the molecule chain length on the tunnel resistance and the TMR (Figure 1b) [5]. These results confirm the high quality of the devices and unravel the potential of self-assembled monolayers as tunnel barrier for conventional spintronics applications and beyond, such as spinOLEDs which relies on spin injection at high bias voltage. However, as LSMO’s surface Curie temperature (Tc) is close to room temperature, spintronics effects in LSMO-based devices are expected only at low temperature. So, in order to obtain spintronics effects at room temperature it will be desirable to substitute LSMO by a ferromagnet of higher Tc, as for example ferromagnetic (FM) metals like cobalt (Co). Unlike LSMO, FM metals readily oxidize and is not surprisingly that SAM grafting protocols over FM electrodes are almost non-existing. The formation of SAMs on bare magnetic metals is a challenging task since surface oxidation (which suppresses surface ferromagnetic properties) during SAMs grafting has to be avoid. In this communication, we present our first results towards the integration of SAMs into room temperature spintronics devices. We have developed the grafting protocols necessary for the integration of SAMs on 3d FM metals with solution approaches. We will present the formation of SAMs on Co under ambient conditions and in inert atmosphere without oxidation of the Co substrate (Figure 2). By standard characterizations it will be probe that only thiol group can be successfully grafted on ferromagnetic surfaces whereas phoshonic acids group works with oxidized metal surfaces.

S. Tatay1,2, A. Forment-Aliaga1, M. Mattera1, H. Prima1, J. P. Prieto1, M. Galbiati2, P. Seneor2, R. Mattana2 and E. Coronado1 [email protected]


References

[1] C. Barraud et al., Nature Phys. 6 (2010) 615 [2] W. Wang and C.A. Ritcher, Appl. Phys. Lett. 86

(2006) 153105

[3] J. R. Petta, S. K. Slater and D. C. Ralph, Phys. Rev. Lett., 93 (2004) 136601

[4] S. Tatay et al., ACS Nano, 6 (2012) 8753 [5] M. Galbiati et al., Adv. Mater., 24 (2012) 6429

Figure 1. a) R(H) characterization of a LSMO/SAM/Co nanojunction at T=2K. b) TMR characterization of a LSMO/SAM/Co nanojunction depending on bias voltage and temperature.

Figure 2. Co2p and O1s high resolution XPS spectra of a Co-SAM sample measured after 20 s of ion milling. In this sample, cobalt was sputtered, the sample was transferred to a glove box, SAM was grafted and the sample transferred again to the sputtering chamber without breaking the inert atmosphere and capped with 10 nm of gold. XPS spectra of oxidized (Co-OX) and unoxidized (Co-UHV) cobalt ahave been added for comparission.

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WPI Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Tsukuba, Ibaraki 305-0044, Japan

The microfabrication size for the conventional semiconductor devices will reach the atomic scale in near future. It is evident that not only the limits to conventional fine processing technology but also the physical operating limits of semiconductor devices are being reached. One possible way to overcome these technological and physical limits of the existing conventional semiconductor devices is to achieve breakthroughs in novel device materials and novel device-operation principle using nanotechnology. A promising type of such nanodevices is the solid-state-nanoionics device, which is operated by controlling the local ion migration and electrochemical reaction in solids. The ionics has been known to be a field in which the local ion transport and electrochemical phenomena are treated and, up to now, it has been different to electronics, which treats the transport phenomenon of the electron and the hole. We have found interesting properties and functions, such as analogue memory property, programming rectification, quantized conductance atomic switch, and nonvolatile resistance switching, in nanoionics devices with simple layer structures [1-9]. These properties and functions are realized by local ion migration in a nanoscale electrolyte layer of electronic-ionic mixed conductors or pure ionic conductors. In this presentation, we will introduce ways to control the local ion migration and electrochemical reaction using the ionic conductor. Furthermore, the unique phenomena and function caused by these nanoionic controlling in order to fabricate novel nanodevices based on stacked layers, such as metallic oxide or graphene oxide/ionic conductor [7-9] are demonstrated.

References

[1] K. Terabe, T. Hasegawa, T. Nakatama, M. Aono, Natute, 433, 47 (2005).

[2] R. Waser, M. Aono, Nature Materials, 6, 833 (2007)

[3] K. Terabe, T. Hasegawa et al., Science and Technology of Advanced Materials, 8, 536 (2007).

[4] T. Sakamoto, K. Terabe, et. al., 91, 092110 (2007)

[5] T. Ohno, T. Hasegawa et al., Nature Materials, 10, 591 (2011).

[6] H. Hasegawa, K. Terabe, et al., Advanced Materials, 24, 252 (2012)

[7] R. Yang, K. Terabe, et.al., ACS NANO, 6, 9515 (2012).

[8] T. Tsuchiya, K. Terabe, M. Aono, Applied Physics Letters, 103, 073110 (2013).

[9] T. Tsuchiya, K. Terabe, M. Aono, Advanced Materials, 26, 1087 (2014)

Kazuya Terabe, Rui Yang, Takashi Tsuchiya, Tohru Tsuruoka, Tsuyoshi Hasegawa and Masakazu Aono

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ICFO – Institut de Ciéncies Fotóniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain

Graphene has many characteristics that make it a highly suitable material for optoelectronic applications, such as photodetection and light harvesting: a tunable carrier density, extremely broadband light absorption and an ultrafast photoresponse, amongst others. Here we assess the ability of graphene to perform high-speed and efficient photon-to-current conversion through photo-induced carrier heating and subsequent current generation through the photo-thermoelectric effect, driven by the hot carriers [1]. First, we discuss the ultrafast (sub-picosecond) energy relaxation process of primary photoexcited e-h pairs in intrinsically doped monolayer graphene [2], as this ultimately defines the carrier heating efficiency. We experimentally quantify the branching ratio between the two competing energy relaxation pathways – optical phonon emission vs. intraband carrier-carrier interaction. The latter process leads to carrier heating as photoexcited carriers transfer their energy to intrinsic carriers in the Fermi sea, which develop into a broader (hotter) distribution. Our ultrafast optical pump – terahertz probe measurements show that carrier-carrier interaction dominates the ultrafast energy relaxation process, when specific requirements concerning the fluence and the Fermi energy are met [3]. We furthermore study basic graphene-based photo-thermoelectric devices that give a photoresponse driven by hot carriers, where we are interested in two key questions: How fast can we create a photoresponse? And how efficient is carrier heating? Using scanning photocurrent microscopy we observe a hot-carrier photocurrent, when we shine light on the interface between monolayer and bilayer graphene [4] or the

interface between graphene of different Fermi energies [1]. Employing an advanced ultrafast time-resolved photocurrent setup with an unprecedented time resolution of ~35 fs, we find that the photo-thermoelectric photovoltage in graphene is created with a time scale <50 fs, corresponding to THz speeds [5]. This ultrafast time scale suggests highly efficiency carrier heating through intraband carrier-carrier scattering. To quantify the efficiency of carrier heating, we measure the energy-resolved photocurrent between 500 and 1500 nm. We observe that when we keep the absorbed power constant, while decreasing the number of incident photons (by decreasing the wavelength of the incident light), the photocurrent signal stays constant. This indicates that the additional energy of each absorbed photon is efficiently transferred to electron heat. Therefore we conclude that due to carrier-carrier scattering dominated ultrafast energy relaxation cascade, the photo-thermoelectric response of graphene devices is ultrafast and carrier heating is highly efficient. These results show that graphene is a promising material for ultrafast, efficient, broadband extraction of light energy into photocurrent, enabling a new class of photo-thermoelectric applications.

References

[1] N.M. Gabor et al. Science 334 (2011) 648 [2] K.J. Tielrooij et al. Nature Phys. 9 (2013) 248 [3] K.J. Tielrooij et al. Submitted (2014) [4] X. Xu et al. Nano Lett. 10 (2010), 562 [5] K.J. Tielrooij et al. In preparation (2014)

Klaas-Jan Tielrooij and Frank Koppens [email protected]


Universitat de Barcelona, C/Martí I Franquès 1, 08028 Barcelona, Spain

When nanoparticles (NP) interact with biological media, such as human plasma or serum, proteins and other biomolecules adsorb on the surface leading to the formation of the so-called “protein-corona”. This spontaneous coating gives a biological identity to the NP determining its fate within the living systems. However, as the NP moves from a biological milieu to another, the corona could change its composition due to possible protein exchanges with other competitive proteins in the new fluid. Here we aim to understand the time evolution of the composition of the protein corona in a three-component simplified plasma. We compare results obtained by three different experimental techniques, (i) Fluorescence Correlation Spectroscopy (FCS), (ii) Differential Centrifugal Sedimentation (DCS) and (iii) MicroScale Thermophoresis (MST), to two independent theoretical approaches, (a) Molecular Dynamics (MD) simulations and (b) Differential Rate Equations (DRE) theory. By using the experimental results for single protein solutions as an input and combining the two theoretical approaches we are able to predict the kinetics of the protein corona. We test a posteriori our predictions by direct measurements, finding an excellent agreement.

Figure 1. Representation of the FCS experimental technique.

Figure 2 Snapshot of the MD simulation box.

Oriol Vilanova, Judith Mittag, Philip Kelly, Joachim Rädler and Giancarlo Franzese [email protected]

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ICFO - The Institute of Photonic Sciences Mediterranean Technology Park. Av. Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona), Spain

Graphene is an attractive material for nanomechanical devices because it allows for exceptional properties, such as high frequencies, quality factors, and low mass. An outstanding challenge, however, has been to obtain large coupling between the motion and external systems for efficient readout and manipulation. Here, we report on a novel approach, in which we capacitively couple a high-Q graphene mechanical resonator (Q ≈ 100.000) to a superconducting microwave cavity. The initial devices exhibit a large single-photon coupling of ∼10 Hz. Remarkably, we can electrostatically change the graphene equilibrium position and thereby tune the single photon coupling and the mechanical resonance frequency by a large amount. The strong tunability opens up new possibilities, such as the tuning of the optomechanical coupling strength on a time scale faster than the inverse of the cavity line width. With realistic improvements, it should be possible to enter the regime of quantum optomechanics.

P. Weber, J. Güttinger, I. Tsioutsios, D.E. Chang and A. Bachtold

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Department of Physics, University of Konstanz, 78457 Konstanz, Germany

Nanomechanical resonators are freely suspended, vibrating bridges with nanoscale diameters. These nanostructures are receiving an increasing amount of attention, both in fundamental experiments addressing the foundations of quantum mechanics and for sensing applications, and show great promise as linking elements in future hybrid nanosystems. In particular, doubly-clamped pre-stressed silicon nitride string resonators are explored as high Q nanomechanical systems enabling room temperature quality factors of several 100,000 in the 10 MHz eigenfrequency range. Electrically induced gradient fields are employed to implement dielectric trans-duction as an efficient way to actuate and probe these nanostrings and to tune their eigen¬frequencies over a wide frequency range [1,2]. The two orthogonal fundamental flexural modes of the string vibrating in- and out-of-plane with respect to the sample surface can be engineered to tune in opposite direction. Thus, both modes can be brought into resonance where a pronounced avoided crossing is observed, indicating that the mechanical modes are strongly coupled. A pulsed measurement scheme is used to analyze the time-dependent evolution of a previously initialized mode as it is tuned across the coupling region. At slow sweep rates, the system adiabatically follows the energy eigenstates, whereas the energy is transferred from one branch to the other during fast sweeps. The measured classical transition probabilities show excellent agreement with Landau-Zener theory [3]. Furthermore, the demonstrated time-domain control allows deep insights into the nanomechanical classical two-mode system defined

by the lower and upper hybrid mode of the avoided crossing. To this end electromagnetic pulse techniques well known from coherent control of two-level systems in atoms, spin ensembles, or quantum bits and the corresponding Bloch sphere picture are introduced to nanomechanical systems [4]. Full Bloch sphere control is demonstrated by Rabi, Ramsey and Hahn echo experiments. Moreover, we find that all relaxation times T1, T2 and T2* are equal. This not only indicates that energy relaxation is the dominating source of decoherence, but also demonstrates that reversible dephasing processes are negligible in such collective mechanical modes. We thus conclude that not only T1 but also T2 can be increased by engineering larger mechanical quality factors. After a series of ground-breaking experiments on ground state cooling and non-classical signatures of nanomechanical resonators in recent years, this may be of particular interest for quantum nanomechanical systems in the context of quantum information processing.

References

[1] Q. P. Unterreithmeier et al., Nature 458, 1001 (2009).

[2] J. Rieger et al., Appl. Phys. Lett. 101, 103110 (2012).

[3] T. Faust et al., Phys. Rev. Lett. 109, 037205 (2012).

[4] T. Faust et al., Nature Physics 9, 485 (2013)

E. M. Weig


Figure 1. Schematic of nanomechanical string resonator dielectrically coupled to a set of gold electrodes.

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1ICFO – The Insititute of Photonic Sciences, 08860 Castelldefels (Barcelona), Spain

2Dep. of Mechanical Engineering, Columbia University, New York, NY 10027, USA

3Dep. of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, USA

4CIC nanoGUNE Consolider, 20018 Donostia-San Sebastián, Spain

5NEST, Istituto Nanoscienze - CNR and Scuola Normale Superiore, 56126 Pisa, Italy

6SPIN-CNR, Via Dodecaneso 33, 16146 Genova, Italy

7National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

8IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain

Graphene plasmonics is an excellent platform for strong optical field confinement with relatively low damping. This enables new device classes for deep subwavelength metamaterials [1,2], single-photon nonlinearities [3], extraordinarily strong light-matter interactions [4] and nano-optoelectronic switches. The problem was that thus far strong plasmon damping was observed [5-7], with both impurity scattering [8] and many-body effects in graphene [5] proposed as possible explanations. This strong damping hindered the further development of graphene plasmonic devices. Using van der Waals heterostructures [9] new methods to integrate graphene with other atomically flat materials have become available. Especially graphene encapsulated between two films of hexagonal boron nitride (h-BN) shows extremely high room temperature transport mobility of charge carriers which is only limited by the scattering with acoustic phonons in the graphene [10]. We show results were we exploit near-field microscopy to image propagating plasmons in high quality graphene encapsulated between h-BN [11]. Frequency dispersion and particularly plasmon damping in real space is determined and we show that these high quality graphene samples show unprecedented low plasmon damping combined with extremely strong field confinement. We identify that the main damping channels are intrinsic thermal phonons in the graphene [12] as

well as dielectric losses in the h-BN [13]. These results are the key for the development of graphene nano-photonic and nano-optoelectronic devices.

References

[1] Z. Fang et al., Nano Lett. 14, 299 (2014). [2] A. N. Grigorenko, M. Polini, and K. S. Novoselov,

Nature Photon. 6, 749 (2012). [3] M. Gullans et al., Phys. Rev. Lett. 111, 247401

(2013). [4] .H.L. Koppens, D.E. Chang, and F.J. García de

Abajo, Nano Lett. 11, 3370 (2011). [5] Z. Fei et al., Nature 487, 82 (2012). [6] J. Chen et al., Nature 487, 77 (2012). [7] P. Alonso-González et al., Science 344, 1369

(2014). [8] A. Principi, G. Vignale, M. Carrega, and M.

Polini, Phys. Rev. B 88, 121405(R) (2013). [9] A. K. Geim and I. V. Grigorieva, Nature 499, 419

(2013). [10] L. Wang et al., Science 342, 614 (2013). [11] A. Woessner, M.B. Lundeberg, Y. Gao et al.,

arXiv:1409.5674 (2014). [12] A. Principi et al., arXiv:1408.1653 (2014). [13] J. D. Caldwell et al., arXiv:1404.0494 (2014).

Achim Woessner1,

M. B. Lundeberg1, Y. Gao2, A. Principi3 ,P. Alonso-González4, M. Carrega5,6, K. Watanabe7, T. Taniguchi7, G. Vignale3, M. Polini5, J. Hone2, R. Hillenbrand4,8

and F. H. L. Koppens1

[email protected] [email protected]


Dept. Enginyeria Electrònica, Universitat Autònoma de Barcelona (UAB), Barcelona, Spain IMEC, Leuven, Belgium

This work addresses the impact of different electrical stresses, BTI (Bias Temperature Instability) and CHC (Channel Hot Carrier) stresses, on the nanoscale electrical properties of the MOSFET gate dielectric. First, thanks to its capability to investigate nanometer-sized regions, CAFM is shown to be powerful enough to evaluate the degradation induced in the different regions of the gate oxide along the channel. In particular, it is demonstrated that, while the BTI degradation is homogeneous, the CHC stress degradation, being higher close to the source (S) and the drain (D). Secondly, when comparing strained and non-strained channel devices, the results show that strained devices are more sensitive to CHC stress than non-strained ones. 1. Introduction With the scaling of the MOSFET dimensions, the electric fields in the device increases, triggering different aging mechanisms, such as CHC, BTI and Dielectric Breakdown (BD) [1]. On the other hand, strain techniques have been presented as one way to enhance carrier mobility [2], though, the effects of CHC and BTI stresses can be enlarged [3]. In this work, the nanoscale electrical properties of the MOSFET gate dielectric are studied with CAFM after BTI and CHC stresses. Since very small areas can be analyzed with this technique, the effect of the stress in the different regions (along the channel) of the gate dielectric will be investigated. The impact of a CHC stress on strained MOSFETs will be also analyzed. 2. Experimental p-MOSFETs (W=0.5μm, L=0.13, 0.5, 1 and 3μm) with a 1.4nm thick SiON layer as gate dielectric

have been analyzed. In strained devices, SiGe at the S/D regions was deposited with a 15% Ge content. Some samples were subjected to CHC stress by applying -2.6V at drain and gate, and some other were subjected to Negative BTI stress (NBTI) by applying -2.6V at the gate, while the other terminals were grounded. After 200 sec electrical stresses, the top electrode of the MOSFETs were removed for the nanoscale electrical measurements. 3. Discussion First, the nanoscale effect of NBTI and CHC stress on the gate oxide electrical properties of non-strained MOSFETs has been compared. Fig. 1a-1c show, respectively, examples of typical current maps obtained at 3.6V on (a) non-stressed, (b) NBTI and (c) CHC stressed MOSFETs (L= 1µm). The measurable gate area has been delimited by a dotted line. Fig. 1d shows the averaged current profiles obtained along the channel for the three devices. After the electrical stress, brighter areas, corresponding to larger currents, were observed (which were related to NBTI and CHC degradation) while mainly noise level was measured in the non-stressed MOSFET. Moreover, the distribution of the leaky sites over the gate region is different for the different stresses. In the NBTI stressed MOSFET, the current shows a homogenous distribution along the channel, while in the CHC stressed device, gate current is especially larger in the regions close to the source and drain, indicating a higher degradation (i.e, a larger defect generation) at these regions. The generated defects close to S and D can be attributed to NBTI and CHC degradation, respectively [4]. Table 1 (a), which shows the dispersion, σ, and average current, <I>, measured

Q. Wu, M. Porti, A. Bayerl, J. Martin-Martínez, R. Rodriguez, M. Nafria, X. Aymerich, E. Simoen [email protected]


in a Wx0.05μm2 region in Fig. 1a-c, located close to S, D and at the center of the channel of the three MOSFETs, further supports these observations. Therefore, these results show that a CHC stress induces non-uniform degradation along the channel, being larger close to S/D, as can be detected by the CAFM. The impact of a CHC stress on strained devices was also studied and compared to that on non-strained ones. Fig. 2 shows the current maps obtained at 4V on non-strained (a and c) and strained (b and d) CHC stressed MOSFETs, with L=3µm (a and b) and L=0.13µm (c and d). Larger currents can be observed in the gate area after the CHC stress compared to fresh devices (not shown), which is indicative of the induced degradation. In the 0.13μm MOSFET, currents can reach the maximum measurable value, indicating that BD was triggered during the CAFM scan because of the larger degradation induced by the CHC stress. In the 3μm MOSFETs, however, the observed leaky sites are not BD spots and can be used to analyze the impact of the stress at the different channel regions. Table 1 (b) shows the average gate current <IG> measured on different devices (L=1μm) in regions close to the S, D and in the center of the channel, from images as those in Fig. 2. Note that, close to S and D, currents are larger, demonstrating again the non-uniform degradation of the CHC stress. Moreover, currents are larger in strained devices, and especially, close to S/D. To quantitatively compare the impact of the CHC stress at the different regions of the channel on strained and non-strained devices, the βG parameter was calculated (Table 1 (b)), defined as βG=(IG,increase, strain – IG,increase, non-strain )/ IG,increase, non-strainx100. This parameter indicates the relative increment of the gate current in strained devices compared to non-strained ones. Note that βG, which is indicative of the impact of the stress, is larger close to S and D, showing that strained MOSFETs and, in particular, those regions subjected to strain (S and D), are more sensitive to CHC stress. 4. Conclusion In this work, CAFM has been used to investigate the impact of CHC and NBTI stresses on non-strained and strained MOSFETs. After electrical stress, larger currents were observed at the gate area, which

have been related to the induced degradation. Depending on the stress, the distribution of leaky sites is different: in NBTI stressed devices the degradation is homogenously distributed along the channel, while in CHC stressed devices, degradation is higher close to S/D. These distributions were also observed in strained devices. Moreover, CAFM images have shown that stressed strained MOSFETs show larger currents, especially close to the junctions, demonstrating that they are more sensitive to an electrical stress.

References

[1] V. Huard, et al, IRPS, pp. 624–633, 2009 [2] P. Verheyen, et al, IEEE Electron Devices

Meeting (IEDM), pp. 886-889, 2005. [3] E. Amat, et al, Microelectron. Eng. Vol. 88, pp.

1408-1411, 2011. [4] Q. Wu, et al, IEEE T. Electron. Dev., accepted to

be published

Figure 1. Typical current images obtained on a (reference) non-stressed (a), NBTI (b) and CHC (c) stressed MOSFETs (L=1 μm). (d) Average current measured along the channel for the non-stressed (circles), NBTI (triangles) and CHC (squares) stressed MOSFETs.

Figure 2. Current images obtained on a L= 3 μm (a, b) and 0.13 μm (c, d) MOSFETs with a non-strained (a, c) and strained (b, d) channel after CHC stress.

Table 1, (a) Average and dispersion of the current measured at

a region close to S,D and in the center of the channel of Fig.1. (b) Average gate current <IG> and βG values obtained with CAFM close to S,D and in the center of the channel for strained and non-strained devices (L=1μm).

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1School of Chemistry, Trinity College Dublin, Dublin 2, Ireland

2Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and

Advanced Materials and BioEngineering Research (AMBER) Centre, Trinity College Dublin, Dublin 2, Ireland 3University of Siegen, Hölderlinstrasse 3, 57076 Siegen, Germany

4Dipartimento di Ingegneria dell’Informazione, Università di Pisa,

Via G. Caruso 16, 56122 Pisa, Italy

In recent years, molybdenum disulfide (MoS2), a semiconducting layered transition metal dichalcogenide (TMD), has been identified as one of the most promising two-dimensional (2D) materials for nanoelectronic applications because of its properties which can be tuned by controlling the number of layers.[1-3] Monolayer MoS2 has a direct band gap of ~1.8 eV and bulk MoS2 has an indirect band gap of ~1.3 eV,[1] and electronic devices based on mono- or multilayered MoS2 films have shown good photodetection capability.[3, 4] While mechanical exfoliation is a widely used method to prepare layered MoS2 thin films, the difficulty of controlling layer thickness and the lateral size limitation have led to the development of alternative synthesis routes. Recently, large-area growth techniques based on vapor phase sulfurization of thin Mo films have been adopted for the synthesis of MoS2 thin films.[5, 6] In this study, we introduce a vertically-stacked hybrid photodiode with n-type MoS2 grown by vapor phase sulfurization of pre-deposited Mo films.[7] N-type MoS2 thin films with various thickness are transferred onto p-type silicon (p-Si), producing p-n heterojunction diodes. The effect of varying the incident light intensity, wavelength and MoS2 film thickness is investigated. Current-voltage measurements reveal that the n-type MoS2/p-Si diodes have good rectifying behavior as well as clear photoconductive characteristics. In addition, it is found that the photocurrent of the device has a strong dependence on the MoS2 film thickness. The spectral response of the device shows that there are contributions from direct and indirect band transitions in the multilayer MoS2 film. Further, we

observe a blue-shift of the spectral response into the visible range. The results are a significant improvement in the fabrication of devices from 2D TMDs and opens up a wide range of device applications for future nanoelectronics.

References

[1] K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, Phys. Rev. Lett. 105 (2010), 136805.

[2] B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, Nat. Nanotechnol. 6 (2011), 147.

[3] H. S. Lee, S.-W. Min, Y.-G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, Nano Lett. 12 (2012), 3695.

[4] O. Lopez-Sanchez, D. Lembke, M. Kayci, A. Radenovic, and A. Kis, Nat. Nanotechnol. 8 (2013), 497.

[5] Y.-H. Lee, X.-Q. Zhang, W. Zhang, M.-T. Chang, C.-T. Lin, K.-D. Chang, Y.-C. Yu, J. T.-W. Wang, C.-S. Chang, L.-J. Li, and T.-W. Lin, Adv. Mater. 24 (2012), 2320.

[6] Y. Zhan, Z. Liu, S. Najmaei, P. M. Ajayan, and J. Lou, Small 8 (2012), 966.

[7] C. Yim, M. O’Brien, N. McEvoy, S. Riazimehr, H. Schäfer-Eberwein, A. Bablich, R. Pawar, G. Iannaccone, C. Downing, G. Fiori, M. C. Lemme, and G. S. Duesberg, Sci. Rep. Just accepted (09 June 2014), DOI: 10.1038/srep05458

Chanyoung Yim1,2, M. O’Brien1,2, N. McEvoy2, S. Riazimehr3 , H. Schäfer-Eberwein3, A. Bablich3, R. Pawar4, G. Iannaccone4, C. Downing2, G. Fiori4, M. C. Lemme3 and G. S. Duesberg1,2 [email protected]


Figure 1. Schematic diagram of the n-type MoS2/p-Si diode (left) and semi-logarithmic plot of its current-voltage measurement data in dark and illuminated condition (right).

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1Department of Materials Science and Engineering, Izmir Institute of Technology,

Izmir 35430, Turkey 2Microstructural Analysis Unit, School of Physics and Advanced Materials, University of

Technology Sydney, PO Box 123, Broadway NSW 2007, Australia

This presentation consists of two main parts: (1) the preparation, characterization and optimization of nanostructures/nanosandwiches for the basic understanding of their optical properties and the development and testing of nanosandwiches as model biosensors; (2) synthesis of gold nanorods and changing the growth process to produce nanoparticles and nanobubbles. Noble metal nanoparticles have received a great deal of interest for their optical and plasmonic properties. These properties, which depend on size and structure, have brought a great potential in nanoelectronics and nano-biosensors.[1] This study reveals that nanoparticles in the form of triangle nanosandwiches prepared using natural lithography [1] or in the form of nanorods/nanobubbles prepared by wet chemistry have important optical properties and that the enhanced sensitivity of their surrounding environment can be used as a new class of optical sensors using Localized Surface Plasmon Resonance (LSPR) spectroscopy (Figure 1) The second part of the study was to develop new synthetic methods for preparation of plasmonically active nanoparticles (NPs) such as nanorods (NRs) and nanobubbles. Different nanostructures exhibited varying optical properties owing to their shapes (Figure 2). Finally, the gold nanorods were conjugated with nanodot arrays for development of a nanoscale mechano-optical device Acknowledgment We thank the the Scientific and Technological Research Council of

Turkey (TUBITAK) (112T507 and 110T759 ) for financial support

References

[1] H.M. Zareie et al., ACS Nano 2, 8 (2008).

Figure 1. (A) Schematic illustration of mixed SAM functionalized nanosandwiches and streptavidin detection above the LCST. (B-C) AFM images of unfunctionalized and functionalized nanosandwiches. (D-E) LSPR measurements of unfunctionalized and functionalized nanosandwiches.

Figure 2. SEM micrographs of nanobubbles.

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Hadi M. Zareie1,2 [email protected]

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J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i. Dolejskova 3, CZ-18223 Prague 8, Czech Republic

TiO2 films attract attention because of their interesting mechanical, chemical, electrical and optical properties, which find various applications particularly in photocatalysis and dye sensitized solar cells [1] (DSCs). The performance of DSCs is controlled by the transport of holes from the photooxidized dye on the photoanode towards the counterelectrode. Solar conversion efficiency of the device is limited by the back reaction (recombination) of injected electrons with the oxidized form of mediator taking place mainly at the FTO/TiO2 interface [2]. To avoid recombination losses a compact blocking underlayer of TiO2 is deposited on top of FTO. Besides the blocking effect, the compact layer can improve the adhesion of the FTO/TiO2 interface as well, and creates more electron pathways from the porous layer to FTO and subsequently increases the electron transfer efficiency. Exceptionally dense TiO2 films can be prepared via dip-coating from a sol containing poly(hexafluorobutyl methacrylate) as the structure directing agent [3]. The films cover perfectly even rough surfaces due to thixotropic properties of the precursor gel (Figure 1). They are mechanically and chemically stable, scratch-resistant and provide antireflection function to crystalline Si wafers for photovoltaic applications. The dense TiO2 films contain amorphous titania with small amount of anatase and monoclinic TiO2(B). These two phases withstand calcination at 900oC in films deposited on Si and no recrystallization to rutile occurs. The blocking properties of the films were tested by cyclic voltammetry using Fe(CN)3-/4- in aqueous electrolyte solution [4]. The occurrence of anodic current of ferrocyanide oxidation selectively indicates the naked FTO substrate, which is exposed to the electrolyte solution through pinholes, if any in the blocking layer. The as-grown films were found to exhibit an excellent rectifying

interface with almost no pinholes. However, defects were formed by thermal treatment at 500oC in air due to anatase crystallization. The overall area of thermally induced pinholes is comparable to that in frequently used spray-pyrolyzed titania films. The above mentioned results favor as made sol-gel compact TiO2 layers being an efficient blocking underlayer in classical liquid junction DSCs. Since the optimum buffer layer for practical solid-state and the most recent perovskite solar cells is predicted to be at the interplay of quasi-amorphous morphology (responsible for the good blocking function) and anatase crystallinity (responsible for the fast electron injection and transport in the conduction band), our sol-gel dense layers treated by optimized calcination procedure can meet requirements for buffer layers of these devices as well. Acknowledgements This work was supported by the Grant Agency of the Czech Republic (contracts No. 13-07724S and P108/12/814).

References

[1] Zukalova, M.; Zukal, A.; Kavan, L.; Nazeeruddin, M. K.; Liska, P.; Gratzel, M. Nano Letters,5, 9 (2005), 1789-1792.

[2] Yuan, S. J.; Li, Y. G.; Zhang, Q. H.; Wang, H. Z. Electrochimica Acta, 79, (2012), 182-188.

[3] Prochazka, J.; Kavan, L.; Zukalova, M.; Janda, P.; Jirkovsky, J.; Zivcova, Z. V.; Poruba, A.; Bedu, M.; Döbbelin, M.; Tena-Zaera, R. Journal of Materials Research,28, 03 (2012), 385-393.

[4] Kavan, L.; Zukalova, M.; Vik, O.; Havlicek, D. Chemphyschem,15, 6 (2014), 1056-61.

Marketa Zukalova, Jan Prochazka, Pavel Janda and Ladislav Kavan [email protected]


Figure 1. SEM pictures of crystalline (111) Si-substrate etched (textured) for photovoltaic applications: A) Blank Si-substrate B) Si-substrate dip coated from a Pluronic-P123 containing precursor sol. C) Si-substrate dip coated from the poly(hexafluorobutyl methacrylate) containing precursor sol (Reprinted from Ref.3).

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Graphenea S.A., Tolosa Hiribidea 76, Donostia - San Sebastian, Spain

During the last decade graphene has shown tremendous potential to be applied in many different fields. However, graphene is currently still at a research stage, mainly laboratory scale experiments are being carried out. Nevertheless, some applications will be ready to move to pilot scale studies very soon. We should keep in mind that an advanced material could take an average of 20 years to succeed in the industrial market. [1] During this talk I will cover some of the progress that has occurred in graphene applications [2-4] such as in transparent electrodes [2] where graphene has the advantage of added flexibility but has to guarantee performance similar to that of ITO in terms of sheet resistance and transmittance. In order to use graphene as ITO replacement material it has be doped since the conductivity of pristine graphene is very low. Stable doping of graphene [2,5] is a clear challenge and it could be the reason why there are not mobile phones in the market using graphene as the transparent conductor. In addition, graphene in biosensing, as a substrate for semiconductor material growth, etc. will also be presented.

References

[1] H. Alcalde, J. de la Fuente, B. Kamp and A. Zurutuza, Proc. of the IEEE, 101 (2013) 1793.

[2] J. Meyer, P.R. Kidambi, B.C. Bayer, C. Weijtens, A. Kuhn, A. Centeno, A. Pesquera, A. Zurutuza, J. Robertson and S. Hofmann, Sci. Rep., 4 (2014) 5380.

[3] T. Araki, S. Uchimura, J. Sakaguchi, Y. Nanishi, T. Fujishima, A. Hsu, K.K. Kim, T. Palacios, A. Pesquera, A. Centeno, and A. Zurutuza, Appl. Phys. Express, 7 (2014) 071001.

[4] O. Zagorodko, J. Spadavecchia, A. Yanguas Serrano, I. Larroulet, A. Pesquera, A. Zurutuza, R. Boukherroub and S. Szunerits, submitted.

[5] L. D’Arsié, S. Esconjauregui, R. Weatherup, Y. Guo, S. Bhardwaj, A. Centeno, A. Zurutuza, C. Cepek and J. Robertson, Appl. Phys. Lett., 105 (2014) 103103

Amaia Zurutuza [email protected]


Catalan Institute of Nanoscience and Nanotechnology, CIN2, ICN2 (CSIC-ICN) Campus UAB, E-08193 Bellaterra (Barcelona), Spain

There are multiple and varied challenges to allow for our inexorable transition to a sustainable energy model, a model that will include new ways of generating, storing, distributing, managing and consuming energy. These new ways are already emerging but they need a definitive boost to prevail. Science and Technology, and in particular Nanoscience and Nanotecnology are bound to provide great and many contributions to the consolidation of these emerging technologies. At ICN2 we are actively working on many fronts related to nanomaterials for energy conversion, storage and efficiency and will present here an overview of these efforts, including next-generation fotovoltaics,[1,2] high-performance lithium batteries and fast-charging supercapacitors, [3,4] biogas production,[5] materials for fuel cells,[6, 7] for thermoelectric energy harvesting[8] as well as materials for energy saving.[9]. All of them examples of how to walk the steep way that goes from nanometers to terawatts.

References

[1] Vertically-aligned nanostructures of ZnO for excitonic solar cells: a review Gonzalez-Valls, Irene; Lira-Cantu, Monica. EN & ENV SCI 2 (1) 19-34, 2009.

[2] Low-temperature, solution-processed, layered V2O5 hole-transport layer for organic solar cells Teran-Escobar, Gerardo; Pampel, Jonas; et al. EN & ENV SCI 6(10) 3088-3098 2013.

[3] Hybrid Energy Storage: The Merging of Battery and Supercapacitor Chemistries. Dubal, D.P.; Ayyad, O.; Ruiz, V; Gomez-Romero, CHEM SOC REV in press 2014.

[4] Stable graphene - polyoxometalate nanomaterials for application in hybrid supercapacitors Suarez-Guevara, J; Ruiz, V; Gomez-Romero, P PHYS CHEM CHEM PHYS 16(38) 20411-20414, 2014.

[5] Programmed Fe3O4 Nanoparticles Disintegration in Anaerobic Digesters Boosts Biogas Production Casals, Eudald; Barrena, Raquel; Garcia, Ana; et al. SMALL 10(14) 2801-2808, 2014.

[6] Proton-conducting Poly-benzimidazoles for high-temp PEM fuel cells. A chemical quest Asensio, J. A; Sanchez, Eduardo M.; Gomez-Romero, Pedro CHEM SOC REV 39(8) 3210-3239 2010.

[7] Deposition and characterisation of epitaxial oxide thin films for SOFCs Santiso, Jose; Burriel, Monica. J SOLID STATE ELECTROCHEM 15(5) 985-1006, 2011.

[8] Nanostructured p-type Cr/V2O5 thin films with boosted thermoelectric properties Loureiro, Joana; Santos, Joao R.; Nogueira, Adriana; et al. J. MAT CHEM A 2(18) 6456-6462, 2014

[9] Liquid-Filled Capsules as Fast Responsive Photochromic Materials Vazquez-Mera, N; Roscini, C; Hernando, J; et al. ADV OPT MAT 1(9) 631-636 2013.

Pedro Gómez-Romero [email protected]

Discovery at the Information LimitComplete materials insight down to the atomic scale

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[110] [110]

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[121] [121]

Edited By

Alfonso Gómez 17

28037Madrid – Spain

[email protected]

www.phantomsnet.net

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