The O₂-dependent growth of ZnO nanowires and their photoluminescence properties

ZnO nanowires were massively synthesized on a Ni(NO₃)₂-coated silicon substrate under oxygen-containing argon atmosphere by a simple chemical vapor deposition method. The average diameter of the ZnO nanowires was about 50 nm and the average length was about 20 μm. The morphologies of the ZnO nanowires strongly depended on oxygen content in the growth atmosphere. At low oxygen concentration (about 5-10 ppm), ZnO nanocones and nanoneedles were obtained, while at high oxygen concentration (about ∼250 ppm), ZnO nanoparticles deposited on the substrate. The room temperature photoluminescence (PL) spectrum of the ZnO nanowires revealed that a strong UV band at 384 nm dominated the whole spectrum. These results indicate that the ZnO nanowires grown under oxygen-containing atmosphere possess better crystalline quality and UV luminescence properties than those grown in reducing hydrogen atmosphere. Based on the analysis of oxygen effect on the ZnO nanostructures, a vapor-liquid-solid mechanism assisted by the redox growth mode was proposed to understand the growth of the ZnO nanowires.