Title: Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays Zhong Lin Wang1,2,3* and Jinhui Song1 14 APRIL 2006 VOL 312 SCIENCE
1Piezoelectric Nanogenerators Basedon Zinc Oxide
Nanowire ArraysZhong Lin Wang1,2,3 and Jinhui
Song114 APRIL 2006 VOL 312 SCIENCE
- Presented by
- Yiin-Kuen(Michael) Fuh
2Outline
- Motivation Background
- Experimental design
- Results
- Conclusion
3Motivation Background
- Motivationself-powered device can greatly reduce
the size of integrated nanosystems for
optoelectronics, biosensors and more. - Background
- 1D ZnO nanomaterials
- exhibits both semiconducting and
piezoelectric(PZ) properties for
electromechanically coupled sensors and
transducers. - is relatively biosafe and biocompatible for
biomedical applications. - exhibits the most diverse and abundant
configurations of nanostructures knownsuch as
NWs, nanobelts (NBs) ,nanosprings, nanorings,
nanobows and nanohelices (10). - The mechanism of the power generator relies on
the coupling of piezoelectric and semiconducting
properties of ZnO as well as the formation of a
Schottky barrier between the metal and ZnO
contacts.
4Experimental design
- Aligned ZnO NWs grown on -Al2O3 substrate.
- (B) TEM image showing the NW without an Au
particle or with a small Au particle at the top.
Each NW is a single crystal and has uniform
shape. Inset at center an electron diffraction
pattern from a NW. Most of the NWs had no Au
particle at the top. Inset at right image of a
NW with an Au particle - (C) The base of the NW is grounded and an
external load of RL is applied, which is much
larger than the resistance RI of the NW. The AFM
scans across the NW arrays in contact mode
Experimental design for converting nanoscale
mechanical energy into electrical energy by a
vertical piezoelectric (PZ) ZnO NW.
5Results-Electromechanically coupled discharging
process observed in contact mode.
- (A) Topography image, NW density 20/um2
- (B) Output voltage , Vpeak6-9mV
- (C) A series of line profiles of the voltage
output signal when the AFM tip scanned. - (D) Line profiles from the topography (red) and
output voltage (blue) images across a NW. The
peak of the voltage output corresponds
approximately to the maximum deflection of the
NW, indicating that the discharge occurs when the
tip is in contact with the compressed side of the
NW. - (E)Vpeak of FWHM .
- (F) WelasticWPZDWvib. , WPZD0.5CV2
- ?WPZD/Welastic 17-30
6Results-Electromechanically coupled discharging
process observed in tapping mode.
- (A) Experimental setup.
- (B) Topography image
- (C) Output voltage. The voltage output contains
no information but noise, proving the physical
mechanism demonstrated
7Theory --Transport is governed by a
metal-semiconductor Schottky barrier for the PZ
ZnO NW
- (A) NW coordination system.
- (B) Longitudinal strain z distribution (NW of
length 1 µm and an aspect ratio of 10). - (C) induced electric field Ez distribution
- (D) Potential distribution due to PZ effect.
- Schottky rectifying behavior (E) is to separate
and maintain the charges as well as build up the
potential. The process in (F) is to discharge the
potential and generates electric current. - The PZ potential is built up in the displacing
process (G), and later the charges are released
through the compressed side of the NW (H). - (I) Large Au particle The charges are gradually
"leaked" out, no accumulated potential will be
created.
8Conclusion
- Self-powering nanotechnology ? Estimated power
10 pW/µm2 and much more power if drives
resonantly! - Use flexible substrate for scavenging energy
produced by acoustic waves, ultrasonic waves, or
hydraulic pressure/force or environment etc. for
applications such as implantable biomedical
devices, wireless sensors, and portable
electronics - Continued work published as Direct-Current Nano
generator Driven by Ultrasonic Waves Science 6
April 2007Vol. 316. no. 5821, pp. 102 105 - Nanogenerator is featured in the overview section
in the NSF FY 2008 budget request to congress