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Title: Synthesis and characterization of zinc oxide nanowires
Author: Pung, Swee Yong
ISNI:       0000 0004 2722 5111
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2010
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A rapid expansion in research work on zinc oxide nanowires (ZnO NWs) has been observed in recent years. The unique properties of wide bandgap and large exciton binding energy make ZnO NW s suitable for a wide range of devices, such as transistors, photodetectors, light-emitting diodes and laser diodes that operate in the blue and ultraviolet region of the spectrum. Currently, the principal development of ZnO NWs is focused on the gold (Au) catalyst and heteroepitaxial approach. However, the presence of Au may generate undesired deep level traps in the ZnO bandgap, which can be very harmful to the performance of transistors. The objective of this project is to synthesize undoped/doped ZnO NWs via homoepitaxial growth without using a foreign catalyst by Chemical Vapour Deposition (CVD) technique. A modified CVD process using Zn powder as the precursor has been established to produce high density by area of ZnO NWs. This modified CVD technique was reliable for the growth of NWs as suggested by the single factor Analysis of Variance. Both highly (00.2) oriented ZnO seed layer and slow growth processing conditions were the key requirements for growing vertically aligned ZnO NWs via the homoepitaxial approach by this modified CVD technique. The (00.2) dominant ZnO seed layers was deposited by the Atomic Layer Deposition technique. These seed layers had a smooth surface (RMS roughness: 2.850 nm), high transmittance (89.9±6.7%) and low film resistivity (4.l31xl0'3 The growth ofself-catalyzed ZnO NWs was governed by the Vapour-Solid mechanism whereas a combined Vapour-Liquid-Solid and Vapour-Liquid mechanism was more appropriate in describing the growth mechanism of Au-catalyzed ZnO NWs. The surface energy of crystal planes which relate to the effectiveness of capturing adsorbed atoms determined the growth rate and proportion of crystallographic planes of self-catalyzed ZnO NWs. Lastly, in-situ Al doping on ZnO NWs has been demonstrated for the first time using Aerosol Assisted Chemical Vapour Deposition technique.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available