1. Synthesis and characterization of
individual ZnO nanowires
M. Duchamp

2. “Nano” applications
MEMs device to measure ZnO Piezoelectronic
nanowires Young’s modulus
Field Effect Transistor (FET)
Xudong Wang et al. Nano Lett., Vol. 6, No. 12, 2006
R. Agrawal et al. Nano Lett., Vol. 8, No. 11, 2008

3. “Nano” applications
• Direct-Current nanogenerator driven by
ultrasonic waves
Xudong Wang, et al. Science 316, 102 (2007)

4. Top-Down approach
• Today technology: last Intel node
Improved transistor density by 2
• Complex and expensive processes
• Need of new materials

5. ZnO attractive properties
• Hexagonal wurtzite structure
• ZnO can be used as UV or blue emitting
materials
• Transparent in visible spectrum
• Wide band gap: 3.36 eV at room temperature
• Young’s modulus: 140 GPa

6. Chemical Vapor Deposition Synthesis
• Using Vapor-Liquid-Solid (VLS) growth mode
Dissolution
Diffusion
Super-saturation
Oxidation
900°C for 20 minutes
Argon and Oxygen gas

7. Diameter control
 Minimum achievable diameter: 40nm

8. Gold colloid catalysts
Density of
Chemical
colloid
functionalization
∞
silicon substrate
Immersion
time

9. Zinc precursor
How did we chose the Influence of zinc/oxygen
reaction temperature? ratio in the gas phase
ZnO (s)
Zn (g)
Lan Hong et al. Scandinavian Journal of Metallurgy, 171–176, 2006

10. Rajoute diffraction pattern
Crystallographic orientation
Sapphire (001) SrTiO3 (110)
C-axis
Lattice mismatches :
Silicon (100) Lattice mismatch : 18.8% 1% and 9%

11. Dielectrophoresis of ZnO nanowires
Parameters studied:
• Dispersion
• Solvents
Repartion [%]
• Substrates
• Applied voltages
Number of attracted Nws
 Number of ZnO nanowires between electrodes can
be controlled by the applied voltage
M. Duchamp, Kyumin Lee et al. in preparation

12. Electrical measurements: contact effects
Lithography
Contact oxidation
lift-off processes
 Nitrogen doped Cr is
used as metal
 Cannot be oxidized
Allen et al. Appl. Phys. Lett. 94 (2009)

13. Energy level in semiconductors
• Schottky diode
• Electron affinity ZnO: 4.5eV
• Work function Cr: 4.5eV

14. Transport measurements
2 eV

15. Optical measurements
Catholuminescence by Scanning
Photoluminescence Tunneling Microscopy
3.3eV
ZnO1
1.0 ZnO3
ZnO4
ZnO2
Intensity (a.u.)
0.8
2.1eV
0.6
0.4
3.3eV 2.4eV
0.2
0.0
200 400 600 800 1000 1200 1400
Wavelength (nm)
Excitation: 330-360 nm
Optical gap: 2.3eV

16. Mechanical properties
TEM compatible substrate
32nm
120GPa

17. Young’s modulus of ZnO nanowire
Catalyst free growth
by CVD in oxygen rich
atmosphere
32nm
40nm
Young ‘s modulus higher
than bulk value
C. Q. Chen et al. PRL 96, 075505 (2006)

18. Conclusions
• Control of the synthesis:
– Diameter, Shape, Length
• Semi-conducting properties of ZnO grown by
VLS method have been extracted fom a single
nanowire
• Young modulus enhanced for stoichiometric
nanostructures