Vapour-transport-deposition growth of ZnO nanostructures: switch between c-axial wires and a-axial belts by indium doping

摘要

ZnO nanowires and nanobelts are two representatives of one-dimensional semiconductor nanomaterials possessing potential applications as optoelectronic and sensor devices. In this study, we applied a vapour-transport-deposition method to synthesize both types of nanostructures using relatively low temperatures (860 deg C) by controlling the source materials. We found that the resulting product under similar growth conditions can be switched between [0001]-axial nanowires and (1120)-axial nanobelts simply by adding indium to the source. The former appear as ordered vertical arrays of pure ZnO while the latter are belts without spatial ordering. Both represent defect-free single crystals grown via the vapour-liquid-solid mechanism using nanosphere lithography-fabricated catalyst Au templates. Examination of the early growth stage suggests that the dissolution of In into Au influences the nucleation of ZnO at the solid-liquid interface, and subsequently defines the structure and crystallographic orientation of the nanobelts. The optical properties of both nanostructures are studied by photoluminescence and resonant Raman scattering, which indicate consistently that the doped nanobelts have a higher carrier concentration than the nanowires.