Large-Scale Synthesis of Bicrystalline ZnO Nanowire Arrays by Thermal Oxidation of Zinc Film: Growth Mechanism and High-Performance Field Emission

Understanding the origin crystal nucleation and driving force is critical for the synthesis of one-dimensional nanomaterials with controllable size, morphology, and crystal structure. The growth behavior of ZnO nanowires prepared by thermal oxidation of zinc film is studied. It is found that the grown nanowires have a bicrystalline structure and growth direction significantly different from the commonly observed [0001] direction. On the basis of detailed high resolution morphology and structural analysis, we propose the origin of the initial growth site, as well as the driving force for formation of the bicrystalline structure of aligned ZnO nanowires. The initial zinc film plays an important role in the growth of nanowire. The edge-enhanced oxidation effect of zinc grain initiates the ZnO nanowire nucleation. The strain within the ZnO layer drives and stimulates the nanowire growth. The present study provides insight into the growth mechanism of ZnO nanowires grown from thermal oxidation of zinc film. Field emission measurement results show that the prepared ZnO nanowires have excellent field emission properties. Uniform emission can be obtained and the turn-on field is 7.8 V/mu m. The results indicate that the method is advantageous for large-scale synthesis of ZnO nanowires for field emission applications.