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Piezoelectric Nanogenerators Based

on Zinc Oxide Nanowire ArraysZhong Lin Wang1,2,3* and Jinhui Song1

14 APRIL 2006 VOL 312 SCIENCE

P!"!n#!d $%

&iin'(u!n)i+ha!- .uh

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Outline

Motivation & Background

Experiental design

!esults "onclusion

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Motivation & Background

o#i/a#ion#sel$%powered device can greatly reduce te size o$integrated nanosystes $or optoelectronics' (iosensors and ore)

a+gound#* +, ZnO nanoaterials

exi(its (ot seiconducting and piezoelectric-PZ. properties $or

electroecanically coupled sensors and transducers) is relatively (iosa$e and (iocopati(le $or (ioedical applications) exi(its te ost diverse and a(undant con$igurations o$

nanostructures knownsuc as N/s' nano(elts -NBs.'nanosprings' nanorings' nano(ows and nanoelices -+0.)

* 1e ecanis o$ te power generator relies on te coupling o$piezoelectric and seiconducting properties o$ ZnO as well as te$oration o$ a 2cottky (arrier (etween te etal and ZnO contacts)

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Experiental design

(A) Aligned ZnO NWs grown on-Al2O3 substrate.

(B) TEM image showing the NW

without an Au arti!le or with a

small Au arti!le at the to.

Ea!h NW is a single !r"stal and

has uni#orm shae. $nset at!enter% an ele!tron di##ra!tion

attern #rom a NW. Most o# the

NWs had no Au arti!le at the

to. $nset at right% image o# a

NW with an Au arti!le

(C

) The base o# the NW isgrounded and an e&ternal load

o# R' is alied whi!h is mu!h

larger than the resistan!e R$ o#

the NW. The AM s!ans a!ross

the NW arra"s in !onta!t mode

Experiental design $or converting nanoscale

ecanical energy into electrical energy (y a

vertical piezoelectric -PZ. ZnO N/)

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!esults%Electroecanically coupled discarging

process o(served in contactode)

)A-1opograpy iage' N/ density3405u4

)-Output voltage ' 6peak37%86

-C. A series o$ line pro$iles o$ tevoltage output signal wen te A9Mtip scanned)

-. :ine pro$iles $ro te topograpy-red. and output voltage -(lue. iagesacross a N/) 1e peak o$ te voltageoutput corresponds approxiately tote axiu de$lection o$ te N/'indicating tat te discarge occurswen te tip is in contact wit tecopressed side o$ te N/)

-E.6peak o$ 9/;M ) -.. /elastic

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-A. Experiental setup)

-. 1opograpy iage

-". Output voltage) 1evoltage output containsno in$oration (ut noise'proving te pysicalecanis deonstrated

*esults-Ele!trome!hani!all" !ouled dis!harging

ro!ess obser+ed in tappingmode.

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Theor" --Transort is go+erned b" a metal-

semi!ondu!tor ,!hott" barrier #or the Z ZnO NW -A. N/ coordination syste) -. :ongitudinal strain z distri(ution -N/ o$

lengt + and an aspect ratio o$ +0.) -C. induced electric $ield Ez distri(ution -. Potential distri(ution due to PZ e$$ect)

2cottky recti$ying (eavior )E-is toseparate and aintain te carges as wellas (uild up te potential) 1e process in ).-is to discarge te potential and generateselectric current)

1e PZ potential is (uilt up in te displacing

process )-,and later te carges arereleased troug te copressed side o$ teN/ )-5

-I. :arge Au particleC 1e carges aregradually DleakedD out' no accuulatedpotential will (e created)

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"onclusion

2el$%powering nanotecnology Estiated power3 +0p/54and uc ore power i$ drives resonantlyF

Gse $lexi(le su(strate $or scavenging energy produced(y acoustic waves' ultrasonic waves' or ydraulic

pressure5$orce or environent etc) $or applications sucas iplanta(le (ioedical devices' wireless sensors'and porta(le electronics

"ontinued work pu(lised as H,irect%"urrent Nanogenerator ,riven (y Gltrasonic /aves I Science7 April400?C6ol) @+7) no) >J4+' pp) +04 * +0>

Nanogenerator is $eatured in te overview section in teN29 9K 400J (udget reLuest to congress