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Growth of Vertically Aligned ZnO Nanowire Arrays Using Bilayered Metal Catalysts
NAVAL RESEARCH LAB WASHINGTON DC ELECTRONICS SCIENCE AND TECHNOLOGY DIV
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Vertically aligned, high-density ZnO nanowires NWs were grown for the first time on c-plane sapphire using binary alloys of NiAu or CuAu as the catalyst. The growth was performed under argon gas flow and involved the vapor-liquid-solid VLS growth process.We have investigated various ratios of catalyst components for the NWs growth and results indicate that very thin adhesion layers of Ni or Cu deposited prior to the Au layer are not deleterious to the ZnO NW array growth. Significant improvement of the Au adhesion on the substrate was noted, opening the potential for direct catalyst patterning of Au and subsequent NW array growth. Additionally, we found that an increase of in thickness of the Cu adhesion layer results in the simultaneous growth of NWs and nanoplates NPs, indicating that in this case the growth involves both the VLS and vapor-solid VS growth mechanisms. Energy dispersive X-ray spectroscopy EDX and surface-enhanced Raman scattering SERS studies were also performed to characterize the resulting ZnO NW arrays, indicating that the NWs grown using a thin adhesion layer of Ni or Cu under the Au show comparable SERS enhancement to those of the pure Au-catalyzed NWs.
APPROVED FOR PUBLIC RELEASE