Smart Electronic Materials(optoelectronics)Prof. A. Grishin

Nanopiezotronics for Sensor and Generator Applications Jolien Dendooven Ezio Iacocca Nicolas Innocenti Filip Vanlerberghe

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NanopiezotronicsNano : a word we love!

-tronics : suffix to make it sounds nicerPiezo : stuff we deal with now

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Direct piezoelectric effectDefinition: ability of some materials to generate an electric potential in response to applied mechanical stress.

Ref. [1]

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A question of structureCentrosymmetry Non-centrosymmetry

Ref. [2]4

Converse piezoelectric effect

Ref. [1]

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A link between two worldsElectricity : electrical displacement D=eE

Solid mechanics : Hooke's lawS=sT Piezoelectric material : both laws are coupled! D = dT T + e E S=sT+dE d = new parameter = piezoelectrical constant6

Which material?In nature :Human-made : - some crystals - even some polymers - but mainly ceramics Quartz ==> Watches! Topaz Cane sugar Bones

in particular :

ZnO7

ZnO piezoelectric?Charges ? Structure ? Comes in two different types of crystal Zn2+ O2OK!

Blende

Wurtzite

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Blende

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Blende

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Wurtzite

Structure OK!

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Piezoelectrical ceramic and more...ZnO Bandgap : 3.37 eV ==> Semiconductor

3.37 eV --> 328 nm, UV light ==> Transparent at visible wavelengths

Compatible with optical technologies

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More and more...Other uses of ZnO :

Antiseptic to cure eczema and skin injuriesContraindications : "Do no ingest"

==> Biocompatibility May be used in biological and medical applications

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Principle of nanopiezotronics

Ref. [4]14

ZnO : the perfect materialToday's technology : Silicon Onchip technology limited to electrical-electrical interactions Tomorrow's technology : - broader interactions on chip - optoelectronics - biotechnologies

ZnO :

- key for onchip silicon-mechanics interactions

- compatible with optoelectronics - compatible with biotechnologiesand even more...15

Nanostructures of ZnOZnO can be grown in diverse structures

Nanobelts, nanorings, nanospirals and nanohelicesPatterned growth of aligned nanowires

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Nanobelts: vapor-solid process

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Nanorings and nanospirals

Ref. [5]

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Superlattice-structured nanohelix

Ref. [7]

Superelasticity !

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Patterned growth of aligned nanowires Important for applications Vapor liquid solid process

Ref. [8]

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Patterned growth of aligned nanowiresRandom growth Patterned growth

Ref. [9]

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Ideal growth conditions

The growth direction is controlled by the epitaxial relationship between the substrate and nanowires. Nanowires grown on a silicon substrate are always randomly orientated because the gold catalyst tends to form an alloy with silicon and destroys the singlecrystalline substrate surface. Because of a small lattice mismatch between the Al2O3 substrate and the gold particles, the substrate remains single-crystalline and orient the nanowires vertically. The aligning quality is controlled bythe chamber pressure the oxygen partial pressure the thickness of the catalyst layer.

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Configuration for the applications A pattern of aligned nanowiresfor the generator

A single nanowirefor the PE-FET and the diode

A single nanobeltfor the bulk acoustic resonator

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Nanogenerator Principles Piezoelectric effectStress electric field/potential distribution

Ref. [10]

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Nanowire contacts Bottom ohmic contact: work function < electron affinity of ZnO Top Contact: Schottky diode: work function > electron affinity of ZnO

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Potential build up and discharge made possible by the Schottky barrier

Ref. [10]

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Direct current nanogenerator driven by ultrasonic waves AFM tip replaced by zigzag electrode Vertically alligned array of ZnO NW

Ref. [11]

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Different configuration possibilities of the NW in respect to the zigzag electrode

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Equivalent electrical circuit and experimental results

Ref. [11]

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MOSFET

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PE-FET Piezoelectronic FETDevice overview:

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PE-FET Piezoelectronic FETEffects in the NW:

Ref. [7]

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Sensor Application Mobile electrode NanoNewtons measure

Ref. [7]

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Piezoelectronic Diode

Ref. [7]

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Piezoelectronic Diode Ohmic contact Zener-like behavior 6.6uA reverse current at -5V.

Ref. [7]

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SAW and BARSAW:

BAR:

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NB BAR device

Ref. [7]

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References [1] Piezooptics, http://www.bostonpiezooptics.com/. [2] Zhong Lin Wang, Nanopiezotronics, Advanced Materials, , no. 19, pp. 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. 2633, June 2004. [6] Zhong Lin Wang, Piezoelectric Nanostructures: From Growth Phenomena to Electric Generators, MRS Bulletin, vol. 32, pp. 109116, February 2007. [7] Zhong Lin Wang, The new eld of nanopiezotronics, Materialstoday, vol. 10, no. 5, pp. 2028, May 2007. [8] Nanowire photonics, http://www.nanowirephotonics.com/research-nanowires. html. [9] Xudong Wang, Jinhui Song, and Zhong Lin Wang, Nanowire and nanobelt arrays of zinc oxide from synthesis to properties and to novel devices, Journal of Materials Chemistry,

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References (2) vol. 17, pp. 711720, 2007. [10] Z.L. Wang and J.H. Song, Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays, Science, pp. 242246, April 2006. [11] X.D. Wang, J.H. Song, J. Liu, and Z.L. Wang, Direct-current nanogenerator driven by ultrasonic waves, Science, vol. 316, pp. 102105, 2007. [12] Marc-Alexandre Dubois, Thin lm bulk acoustic wave resonators: a technology overview, MEMSWAVE 03, July 2003. [13] Zinc-oxide, http://www.wikipedia.org/. [14] Jean-Pierre Gaspart, Introduction to Condensed Matter Physics, University of Lige. [15] John Toon, Superlattice Nanobelts, Research horizonts, 2005. [16] Zheng Wei Pan, Zu Rong Dai, and Zhong Lin Wang, Nanobelts of semiconducting oxides, Sience, vol. 291, pp. 19471949, March 2001. [17] Z.L. Wang, Piezoelectric nanogenerators - their principle and potential applications, Physics, vol. 35, pp. 897903, 2006. [18] X.D. Wang, J. Liu, J.H. Song, and Z.L. Wang, Integrated nanogenerators in biouid, Nano Letters, vol. 7, pp. 24752479, 2007. [19] Professor Zhong LinWang's Nano Research Group, http://www.nanoscience.gatech. edu/zlwang/.39