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Northwestern University Rod Ruoff Nanotechnology

High aspect ratio nanostructures: nanotubes, wires, plates, and ribbons


Outline

1. Introduction

2. Nanotubes

3. Nanowires

4. Nanoplates

5. Nanoribbons


Part One:

Introduction


NanostructuresNanostructures are structures that have at least one dimension between 1 and 100 nanometers.

0D nanostructures

- Quantum dots, nano particles and clusters

1D nanostructures

- Nanotubes, nanowires, nanobelts

2D nanostructures

- thin film, nanoplate

www.bobsievers.com/ versailles/p15.html


Other methods: Colloidal Quantum Dots

• Dispersed in solution• Coated with hydrophilic

material (usually glass):– Melt/quench method– Sol/gel method

M. Bruchez, et al., “Semiconductor nanocrystals as fluorescent biological labels,” Science 281, 2013-2016 (1998)T.M. Jovin, “Quantum Dots finally come of Age,” Nature Biotechnology 21, 32-33 (2003)http://ravel.zoology.wisc.edu/sgaap/Bioinformatics_html/Bioinformatics.htm


Part Two: Nanotubes


“armchair”

“zig-zag”

chiral

Structure of Carbon Nanotube (CNT)

Single Wall Carbon Nanotube Structure


Multi-walled carbon nanotube

Single-walled carbon nanotube

Iijima, Nature 1991

Iijima et al;

Bethune et al;

Nature 1993


SEM image of carbon ropes with~10-20 nm diameter andseveral microns in length

More detailed view of cross section of a “singlewalled carbon nanotube bundle,which is comprised of single-wallednanotubes with diameter ~ 1.4 nm.

Thess et al., Science, 1996

Single wall Carbon Nanotubes


CNT: Synthesis

1. Arc Discharge

2. Laser Vaporization (ablation)

3. Chemical Vapor Deposition


CNT: PropertiesMechanical (when defect free):

Young’s Modulus: 1 TPa

Fracture strength: ~100 GPa

Thermal (calculated):

Thermal conductivity: 2000 W/m •K

Electrical:

CNT can be either metal or semiconductor

MWCNTs are typically good conductors: semiconductor with small band gap or metallic


Brittle behavior is observed in MD simulations at low temperature and high strain (Bernholc and coworkers)

Upon increasing strain the tubeis cleaved

Experimentally tubes are seen tobreak at around 5% strain, inagreement with (Bernholc, Yakobson) predictions(Smalley APL, 1999; Ruoff PRL, 2000 )

CNT: Brittle behavior


Arc-grown MWCNT

SEM image of powdered cathode deposit core material with 30-40% MWCNT content from MER Corp.

SEM image of separated MWCNTs on a silicon wafer, after fractionation.

Arc-grown Multi-wall Carbon Nanotubes (MWCNTs) from MER Corp. AZ. (diameter: 5-15 nm, length: 3-5 um.)


CVD-grown Aligned MWCNT Array

Aligned MWCNT arrays were synthesized with PE-CVD method on silicon substrate

Huang et al, Growth of large periodic arrays of carbon nanotubes, App Phys Letter 82(3),2002, 460-462

SEM images of aligned MWCNT array


Template Synthesized Carbon Tubes

(c) Formation of ordered porous alumina layer after second anodization

(d) Coating of a protective layer

(a) Formation of porous alumina layer after first anodization

(b) Removal of porous alumina layer (strip-off)

(e) Removal of aluminum layer

(f) Removal of bottom layer (i.e., barrier layer)

(g) Removal of protecting layer

aluminum alumina protective layerTerry T. Xu, Richard D. Piner, Rodney S. Ruoff, An improved method to strip aluminum from porous anodic alumina films, Langmuir, 2003; 19(4); 1443-1445


TCNT: Porous Anodic Alumina (PAA) Films

Top Surface Bottom Surface Cross section

Terry T. Xu, Richard D. Piner, Rodney S. Ruoff, An improved method to strip aluminum from porous anodic alumina films, Langmuir, 2003; 19(4); 1443-1445


TCNT: Synthesis Strategy


TCNT: Result

Ordered CNTs (after partially dissolving PAA )

TEM image showing two T-CNTs


Bone-shape Carbon Nanotube

Terry T. Xu, Frank T. Fisher, L. Cate Brinson, and Rodney S. Ruoff, Bone-shaped Nanomaterials for Nanocomposite Applications, Nano Letters, 3(8), 1135 -1139, 2003


BCNT: Cross-section


BCNT: TEM Image


Part Three: Nanowires


Crystalline Boron Nanowire

SEM image of boron nanowires on alumina substrate TEM image of a boron nanowire

Otten, Carolyn Jones; Lourie, Oleg R.; Yu, Min-Feng; Cowley, John M.; Dyer, Mark J.; Ruoff, Rodney S.; Buhro, William E., Crystalline Boron Nanowires, Journal of the American Chemical Society, (2002),124(17),4564-4565.


Boron nanowires and nanotubes

Catalysts-assisted growth of boron nanowire-nanotube hybrid structure was discovered.

• Experiment– Method: Chemical Vapor Deposition (CVD)– Precusor: diborane (B2H6)– Substrate: Si with one-micron-thick SiO2– Catalyst: gold (Au), Pt/Pd alloy (nominal 80:20, Pt:Pd)– Pressure: ~200 mtorr– Temperature (center position of the tube furnace): 900°°°°C

• Results– Interesting boron nanowire-catalyst-nanotube hybrid structure was

discovered. Smallest nanostructure was ~ 8-10 nm.– Catalyst geometry in the B nanostructure plays an important role.– Detailed investigation is underway.


morphology• Catalyst-assisted growth of nanowires and nanotubes.• Interesting nanowire-catalyst-nanotube hybrid nanostructures were commonly

observed. • Smaller catalyst smaller nanowires/nanotubes. So far, the smallest one we

can synthesize was about 8-10 nm in diameter.

tube catalystwire

tube

SEM image of nanowire and nanotubes (φφφφ: 30-150nm; Au as catalyst)

tubecatalyst

wire

φφφφ: 15-30nm; Pt/Pd as catalyst.

Terry Xu, Rod Ruoff, to be submitted.


Structure Characterization

Crystalline nanowire Nanowire-catalyst-nanotube hybrid structure (amorphous)

amorphous nanowire

• TEM catalyst shape plays an important role!• EELS boron and small amount of oxygen.• Detail investigation is underway.

Terry Xu, Rod Ruoff, to be submitted.


CaB6: Properties of CaB6

Crystal structure of CaB6

•Crystal structure –CsCl type–B6 octahedra and Ca atoms

•Physical properties–Tm = 2235°C– ρ = 2.43g/cm3–E = 451GPa–ρe = 222µΩ-cm–Vicker hardness = 27GPa

•Applications–Surface protection, wear resistant materials–High neutron absorbability, nuclear industry, etc.


CaB6: Experimental ConditionsLow pressure chemical vapor deposition (LPCVD) growth of CaB6 nanowires

SEM image of CaB6 nanowires

Terry T. Xu, Jian-Guo Zheng, Alan W. Nicholls, Sasha Stankovich, Richard D. Piner, Rodney S. Ruoff, Calcium Boride Nanowires: Synthesis and Characterization, NanoLetters, 4(10), 2051-2055 (2004)

•Reactant: B2H6 gas precursor,CaO powder•Catalyst: Ni, PtPd alloy•Temperature: 850-900°C•Pressure: ~150mtorr•Substrate: Si with 1µm thick SiO2, sapphire, fused quartz


CaB6 : Experimental Results

Nanowires without catalyst on tip880-890°C

TEM images

[001]

Nanowires with catalyst on tip890-900°C

TEM images

Ni catalyst

CaB6 nanowire

[001]

Calcium Boride Nanowires: Synthesis and Characterization Terry T. Xu, Jian-Guo Zheng, Alan W. Nicholls, Sasha Stankovich, Richard D. Piner, Rodney S. Ruoff*, Nano Letters, 4(10), 2051-2055 (2004).


SiC nanowire grown from SiCfibril (supplied by Dick Nixdorf)

“Hairy fibers for composites?


Part Four: Nanoplates


Thin Graphite FilmThin graphite films at the edge of Highly Ordered Pyrolytic Graphite (HOPG).


Thin Graphite Film


X. K. Lu, H. Huang, N. Nemchuk and R. S. Ruoff, Patterning of highly oriented pyrolytic graphite by oxygen plasma etching, Appl. Phys. Lett., 75, 193-195 (1999).

Graphite Platelet


Tin Oxide Disk

Dai ZR, Pan ZW, Wang ZL, Growth and Structure Evolution of Novel Tin Oxide Diskettes, J. Am. Chem,. Soc., 2002, 124, 8673-8680

Type I SnO2 disk

Type II disk with growth feature of terrace and spiral stepsSEM image of SnO disk

SnO diskettes were synthesized by evaporating either SnO or SnO2 powders at elevated temperature (200-400oC).


Part Five: Nanoribbon


ZnO Nanoribbon

Pan, ZW, Dai, ZR, Wang ZL, Nanobelts of semiconducting Oxides, Science, 291(2001), 1947-1949

(a) SEM and (b) TEM images of ZnO nanobelt

Typical width: 30-300 nmWidth to thickness ratio: 5-10


SnO2Nanobelt

Dai, ZR., Pan, ZW., Wang, ZL, Ultra-long single crystalline nanoribbons of tin oxide, Solid State Communication, 118 (2001) 351-354

TEM image of SnO2 nanoribbon Structure model of SnO2 nanoribbon


Ga2O3 Nanoribbon/Nanosheets

Dai ZR, Pan ZW, Wang ZL, Gallium Oxide Nanoribbons and Nanosheets, J. Phys. Chem.B, 2002, 106,902-904

SEM and TEM image of Ga2O3 nanoribbons and nanosheets

Nanoribbons and flat nanosheets of Ga2O3 were synthesized by evaporating GaN at high temperature with the presence of oxygen.


Boron Nanoribbons

Terry Xu

Catalyst-free growth of single crystal αααα–tetragonal boron

nanostructures at relatively low temperature and pressure. Experiment

–Method: Chemical Vapor Deposition (CVD)

–Precusor: diborane (B2H6)

–Substrate: Si with one-micron-thick SiO2

–Pressure: ~200 mtorr

–Temperature (center position of the tube furnace): 900°C

•Results–Puffy ball deposition were observed in the 600-750°C temperature zone region.

–Puffy balls were made of nanostructures having different morphology.

–The nanostructures are single crystal α–tetragonal boron.


Boron Nanoribbon: morphology

Overall view of the puffy ball

“Nano-scrolls” (w: 800-3200nm; t: ~20nm)

Grass-like nanoribbons • twisted, zigzag edges• w: 200-450nm; t: ~20nm Ends of the nanoribbons split into

nanowires (w:20-100nm; t: ~20nm)


Boron Nanoribbon: Structure Characterization

• Diffraction pattern single crystal α–tetragonal boron

• HRTEM crystallized structure covered by a 1 to 2 nm thick amorphous layer

• EELS boron and small amount of oxygen• The amorphous oxide layer was apparently formed

after the sample was exposed to ambient.

TEM image of twisted nanoribbonsHRTEM image and diffraction pattern

EELS spectrum

Terry T. Xu, Jian-Guo Zheng, Nianqiang Wu, Alan W. Nicholls, John R. Roth, Dmitriy A. Dikin, and Rodney S. Ruoff, Crystalline Boron nanoribbons:Synthesis and Characterization, Nano Letters, 2004; 4(5); 963-968.

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High aspect ratio nanostructures: nanotubes, wires, …summerinstitute.mech.northwestern.edu/_links/_courses/Nanoscale...High aspect ratio nanostructures: nanotubes, wires, plates,