Characterizations of the ZnO nanowires grown on the seed layer deposited silicon substrate via vapor transport method

• Main Authors: Jia-Huei Syu, 徐家慧
• Other Authors: Su-Hua Yang
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/25362248681451399140

碩士 === 國立高雄應用科技大學 === 電子工程系 === 99 === The growth and characteristics of the ZnO nanowires, grown on seed layer-deposited silicon substrate via vapor transport method, were investigated. There were three subjects in this study. The first one was to deposit the ZnO seed on the silicon substrate via chemical vapor deposition method; the second was to vary the growth parameters for the synthesis of ZnO nanowires; and the last was to analyze the field emission characteristics of the ZnO nanowires. Using the ZnO seed layer, which replaced to the metal catalysts, could improve the lattice mismatch between the ZnO nanowires and the silicon substrate and supply nucleation sites for the growth of nanowires. From the measurements of X-ray diffraction (XRD), scan emission microscopy (SEM), and energy dispersive spectrum (EDS), it exhibited that the seed layer was consisted of ZnO nano-particals which had a single-crystalline-like structure and an averaged grain size of about 800 nm. For the synthesis of ZnO nanowires, the growth parameters were varied to fine the optimal conditions for nanowires growth, which were the substrate position, growth temperature, the weight ratio of ZnO and graphite powders, together with the growth time, the oxygen flow rate, and the furnace pressure. it exhibited that the oxygen and zinc concentrations were very important factors to grow high crystalline ZnO nanowires. Furthermore, the field emission property of nanostructures was measured. Bright phosphor image was observed from a diode-construction field emission display. The optimal characteristics of nanowires were obtained when the source was a mixture composed of C and ZnO with a concentration ratio of 3:7 wt%; the substrate was right placed on top of the source and the nanowires were grown at 1000℃ for 60 minutes with N2 flow rate 70 sccm and O2 flow rate 50 sccm. The ZnO nanowires, with the best crystallinity, a suitable distribution density, and a long lifetime, had an optimal field emission characteristic and a low turn-on voltage at 0.14 V/μm when the emission current density reaches 0.1 μA/cm2; the field enhancement factor β was 1573.