【摘要】 采用自组装技术,利用均聚极性高分子(聚丙烯酰胺、聚乙烯醇等)长分子链作为自组装模板在半导体硅衬底上自组装生长出ZnO纳米线。采用扫描电镜(FE-SEM)和透射电镜(HRTEM)对样品的表面形貌和结构分析表征的结果表明,ZnO纳米线直径约50~80nm、长度大于4μm,具有六方纤锌矿单晶结构,且沿c轴方向择优取向生长。采用室温下光致发光(PL)谱和紫外吸收(UV)光谱对制得的ZnO纳米线的光学性能研究表明,其PL光谱上有较强的紫外发射和较弱的蓝光发射,UV吸收光谱表明样品在紫外区有强的宽带吸收,且随着纳米线粒径的减小,吸收峰出现了蓝移现象。研究探讨了高分子诱导ZnO纳米线自组装定向生长机制、发光机理及其与工艺条件的内在联系。更多还原

【Abstract】 Zinc oxide (ZnO) nanowires were prepared on silicon substrate via a novel method of polymer complexation-sintering by using polar long-chain polymer (such as PAM and PVA) as self-assembling grid backbone. These ZnO nanowires were characterized by FE-SEM and HRTEM techniques and their optical pro- perties were studied by photoluminescence spectroscopy and UV absorption spectroscopy at room temperature. The mechanism of the ZnO nanowires growth and their photoluminescence, and the relation between process conditions and the mechanism are discussed.The ZnO nanowires, with diameter of about 50~80 nm and the lengths >4 μm, are hexagonal wurtzite single-crystalline and grown along the c-axis orientation preferentially. These nanowires have a strong UV emission band and a weak blue band as well as a strong UV light absorption. With decreasing the nanowires diameter, a blue shift of absorption peak appears.Polymer concentration and the complexing ratio of polymer to Zn 2+ are the key factors controlling the self-assembling growth of ZnO nanowires. The mesh size and distribution of polymers, which are confined by the concentration of the polymer solution, control the diameter of the nanowires. Well vertically grown nanowires initiate only from the site that Zn 2+ is complexed with the polymer, which forms the ideal nuclei, and the nuclei number is dependent on the complexing ratio of the polymer and Zn 2+.The sintering temperature, sintering ambience and annealing condition affect photoluminescence of the ZnO nanowires. By controlling the sintering and thermal annealing conditions, the quality of the nanowires can be improved, and therefore, the better optical properties of the ZnO nanowires can be achieved. In high quality ZnO nanowires, a sharp strong emission peak at ~393 nm appears due to the ultra-violet near band-edge emission of wide band gap ZnO, namely the free-exciton annihilation through an exciton-exciton collision process. The phenomena of UV band emission at room temperature might be attributed to the radial quantum confinement effect from ZnO nanowires. It can be concluded that the improvement of crystal quality, i.e., decrease of impurities and structure defects such as oxygen vacancies, stacking faults and dislocations, and the quantum confinement effect related to the nanostructures are responsible for the intensity increase of the observed UV emission at room temperature.更多还原