ZnO Nanowires from Nanopillars: Influence of Growth Time

A double-tube vapor phase transport system has been used to grow ZnO nanostructures. Nanopillars, nanorods and nanowires of zinc oxide were synthesized on Au nanoparticle catalyst depending on source-substrate distance and temperature gradient in the quartz tube. In addition, influence of growth time and substrate temperature on the morphology of the nanorods and nanowires were also investigated. The scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to further understand the nanostructures growth mechanism on various temperatures and growth time steps. Longer length (>4μm) with hexagonal-cross-sectional nanowires, in [002] growth orientation, were synthesized at low temperatures (875-857°C); while a middle length (<3μm) nanorods were formed at intermediate temperatures (893-875°C). Nanopillars and other irregular nanostructures were also synthesized on the surface at higher temperatures (910-893°C). Based on the TEM observations, the vapor-liquid-solid (VLS) growth mechanism is applied to describe the growth processes for the synthesized nanostructures.