Small is BEAUTIFUL in nanotechnology -the engineering of objects
measuring in the billionths of a meter .
Presented by Aarathy Udayabhanu E7B Roll No :1
16/5/2010
Nano A word we love ! -tronics : suffix to make it sounds nicer
Piezo : stuff we deal with nowWe have
NANOPIEZOTRONICS !
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An Overviewy Introduction y Phenomenon y The Material y The
Fundamental Principles y Nanostructures y Future Applications y
Conclusion y Reference
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How Nanopiezotronics??Piezoelectricity y The ability of certain
crystals to generate a voltage in response to applied mechanical
stress. Electronics y The branch of physics that deals with the
emission and effects of electrons and with the use of electronic
devices. Piezotronics y Field of using piezoelectric-semiconducting
coupled properties/effects for creating/fabricating novel and
unique electronic devices and components .16/5/2010 4
IntroductionNanoelectronics
Today: Future
: Deals with accumulation and movement of charge carriers
:Piezoelectric and electronic property of Zinc oxide
Termed as one of the emerging technologies of 2009 by MIT
Technology review.16/5/2010 5
TOP
The InventorProf. Zhong Lin Wang of Georgia Institute of
Technology
Aim-To power the world with nanoscale sensors using
piezoelectricity. -On success ,biological and chemical sensors will
be able to power themselves .16/5/2010 6
The Phenomenon -PIEZOELECTRICITY
Ability of some materials to generate an electric potential in
response to applied mechanical stress. Eg :PZT,Cane Sugar,GaO
etc16/5/2010 7
Mathematical Descriptiony Combination of Electrical behaviour of
the
material and Hooke s Law. y Electrical Behavior D= E D= Charge
Density =Electrical permitivity E=Electric Field y Hookes LawStrain
S=sT Stress S=Strain s=stiffness T = Stress8
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Contd.both equations, Coupling
[d] is the matrix for the direct piezoelectric effect [dt] is
the matrix for the converse piezoelectric effect. The superscript E
indicates a zero, or constant, electric field The superscript T
indicates a zero, or constant, stress field The superscript t
stands for transposition of a matrix16/5/2010 9
The Materialy Charges ? y Structure ?
Zn2+
O2-
OK!
Comes in two different types of crystal
Blende16/5/2010
Wurtzite10
ZnO StructuresZinc Blende Zinc wurzite
pressure on ZnO Blende will create local dipolar moments for
each dipolar moment created, there exists a symmetrical moment in
the crystal16/5/2010
under pressure, all created dipolar moments will be parallel to
each other resulting in a global polarization
PIEZOELECTRICITY PRESENT
NO PIEZOELECTRICITY
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WURZITE ZnO
HCP structure16/5/2010 12
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WHY ZINC WURZITE???y Wide Band Gap y Green Material y
Piezoelectric and Pyroelectric properties y Longer life time y Low
cost and controlled growth y Availability of large single
crystals
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Fundamental Principlesy Piezoelectric potential y Semiconducting
properties charge separation
and removal y Schottky barrier :metal semiconductor interface y
Ohmic Contact
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CHARACTERISTICS OF PIEZOPOTENTIALy Magnitude - the degree of
deformation. y Polarity switches as the strain is changed y If the
crystal has a point defects :-the
piezopotential is screened16/5/2010 16
How Schottky Barrier?y Zinc oxide -conductive solid substrate. y
AFM:- using a Si tip coated with a Pt film y Pt- Zn : Metal
Semiconductor Interface16/5/2010 17
WHY SCHOTTKY CONTACT ???Pt coated Si tip : voltage peaks were
observed . Al In alloy coated Si tip, NO piezoelectric output Pt
ZnO : a Schottky diode AlIn ZnO : an ohmic contact
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HOW GENERATION OF POTENTIAL TAKES PLACE???? Principle:
NANOGENERATOR16/5/2010 19
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y Basic principle : coupling of the
piezoelectric & semiconducting properties STRAIN outer
surface being tensile : V+ inner surface compressive : V-
y The deflection of the NW by the AFM :
y Initially AFM : Tensile surface : V+ y Pt metal tip
Vm=0,16/5/2010 21
y metal tip Zn : negatively biased
V+)< 0 Reverse biased Schottky diode Little current flows
V=VL = (V m
y AFM tip at compressed side of the NW y metal tip ZnO :
positively biased
V -> 0. Positively biased Schottky diode Sudden Current
V=VL = Vm
y Current : flow of e s from ZnO NW to the metal tip16/5/2010
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y Potetial to convert :i. ii. iii.
mechanical movement energy vibration energy Hydraullic
energy
TO ELECTRICAL ENERGY16/5/2010 23
Things to NOTE:y Use of AFM must be avoided y All NW s have to
generate electricity SIMULTANEOUSLY y Inverted V Electrode
used.16/5/2010 24
Charge Releasing Process
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The AFM tip- (T)- NW :- Schotkky Barrier NW and Ag :-Ohmic
contact (G)
Fig a.
Tip at V+ : e s flow from the grounded electrode :e s cannot
pass reverse biased M-S :accumulated free charges CB : V+Fig c
Fig b
Tip at middle point :PZ potential = 0
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: accumulated e s in the tip flow back :faster than the
charge-accumulation process 26
y Tip at V- : V- drops to V : circular flow of e s in the
external : producing a current : Faster
Fig d
y O/p :-Difference b/w Fermi Energy of Pt and Ag electrode y 5
30 mV depending on NW size and degree of bending16/5/2010 27
Limitationsy Uniformity of nano wires. y Life time
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NANOSTRUCTURES OF ZINCy Belts : systhsized from semiconducting
oxides of
Zn, Sn, In, Cd, etc.y Pure, uniform, single-crystalline, free
from
dislocationsy Used for making nano gas sensors , nano
cantilevers, nano resonators etc.16/5/2010 29
We're talking tiny, not small. The thickness of a human hair
measures about 50,000 nm!!! Synthesisy Controlling a) growth
kinetics b) local growth temperature c) the chemical composition of
source materials y one-dimensional structurally y has well-defined
a) chemical composition, b) crystallographic structure c) surfaces
y single crystalline y dislocation free y surfaces are atomically
flat. 16/5/2010
Nanobelts-
Properties
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Synthesis
Synthesized by solid vapour process The evaporation of ZnO
powder at a higher temperature zone (1400C). Oxide vapor directly
deposits on a Al2O3 and wool like products formed.16/5/2010 31
Nanorings
Nanobelt is grown along a specific direction Top- Zinc and
Bottom Oxygen. Surface charges dipole moments spontaneous
polarization electrostatic energy16/5/2010 32
Applicationsy Smart windows y Flat-panel displays y Electronic
and optical-electronic devices y Sensors
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Would you like to charge your mobile phone without ever having
to plug into an electrical outlet?
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Fiber based NGy Conductive Polymers :substrates
biocompatible b) safe c) Cost effective d) Flexible and
foldablea)
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BASIS OF POWER SHIRT16/5/2010 36
y An array of metal wires y Brushing of metal NW to ZnO NW y
Metal NW = AFM & mechanical
deformations formed. y ZnO NW s grown on Kevlar fibers y Metal
NW should form M-S contact with Zinc NW y Cycled sliding between
two fibers causes output16/5/2010 37
HEARING AID
SIGN VERIFY
POWER SHIRT16/5/2010 38
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Future researchy Increasing the number of active NWs for
participating y y y y
electricity generation Systematic modeling of the charge
generation and transport processes Developing an effective theory
for characterizing the performance of the NG and its efficiency
Improving the packaging technology Study of the failure mechanism
of the NG
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Conclusiony Integrating individual nanodevices into a
nanosystem y The goal is to make a self-powered nanosystem y
Harvesting energy from the environment is a choice for powering
nanosystems y The principle demonstrated in the piezoelectric
nanogenerator could be the foundation
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The day when we can charge our cell phone or iPod just by going
for a stroll around the block could be a step closer.
Thanks to a "nano-generator". "nano-
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Referencey [1] Piezooptics, http://www.bostonpiezooptics.com/. y
[2] Zhong Lin Wang, Nanopiezotronics, Advanced Materials, no. 19,
pp. y y y y y y y y y
889892, 2007. [3] Biam, a French database of medicines for
pharmacist and doctors, http://www.biam2.org/www/Sub1731.html. [4]
Zhong Lin Wang, Electrostatic Potential in a Bent Piezoelectric
Nanowire. The Fundamental Theory of Nanogenerator and
Nanopiezotronics, Nano Letter, vol. 7, no. 8, 2007. [5] Zhong Lin
Wang, Nanostructures of zinc oxide, Materialstoday, pp. 2533, June
2004. [5] Zhong Lin Wang, Piezoelectric Nanostructures: From Growth
Phenomena to Electric Generators, MRS Bulletin, vol. 32, pp.
109115, February 2007. [7] Zhong Lin Wang, The new era of
nanopiezotronics, Materials today, vol. 10, no. 5, pp. 2028, May
2007. [8] Nanowire photonics,
http://www.nanowirephotonics.com/researchnanowires.html [9] Zhong
Lin Wang, Towards Self Powered Nanosystems-From Nanogenerators to
Nanopiezotronics,Advanced Functional Materials,2008 [10] Smart
Electronic Materials,Prof. Grishim, Royal Institute of
Technology,2008 [11] Zhong Lin Wang, The new field of
nanopiezotronics, Materialstoday, vol. 10, no. 5, pp20_28, May
2007.43
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