Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, Kuala Lumpur 50603, Malaysia.
Nanoscale Res Lett. 2013 Apr 17;8(1):174. doi: 10.1186/1556-276X-8-174.
Silicon/zinc oxide (Si/ZnO) core-shell nanowires (NWs) were prepared on a p-type Si(111) substrate using a two-step growth process. First, indium seed-coated Si NWs (In/Si NWs) were synthesized using a plasma-assisted hot-wire chemical vapor deposition technique. This was then followed by the growth of a ZnO nanostructure shell layer using a vapor transport and condensation method. By varying the ZnO growth time from 0.5 to 2 h, different morphologies of ZnO nanostructures, such as ZnO nanoparticles, ZnO shell layer, and ZnO nanorods were grown on the In/Si NWs. The In seeds were believed to act as centers to attract the ZnO molecule vapors, further inducing the lateral growth of ZnO nanorods from the Si/ZnO core-shell NWs via a vapor-liquid-solid mechanism. The ZnO nanorods had a tendency to grow in the direction of [0001] as indicated by X-ray diffraction and high resolution transmission electron microscopy analyses. We showed that the Si/ZnO core-shell NWs exhibit a broad visible emission ranging from 400 to 750 nm due to the combination of emissions from oxygen vacancies in ZnO and In2O3 structures and nanocrystallite Si on the Si NWs. The hierarchical growth of straight ZnO nanorods on the core-shell NWs eventually reduced the defect (green) emission and enhanced the near band edge (ultraviolet) emission of the ZnO.
硅/氧化锌 (Si/ZnO) 核壳纳米线 (NWs) 是在 p 型 Si(111) 衬底上通过两步生长工艺制备的。首先，使用等离子体辅助热丝化学气相沉积技术合成了铟种子涂覆的 Si NWs (In/Si NWs)。然后，使用气相输运和冷凝方法生长 ZnO 纳米结构壳层。通过将 ZnO 生长时间从 0.5 小时延长至 2 小时，在 In/Si NWs 上生长了不同形貌的 ZnO 纳米结构，如 ZnO 纳米颗粒、ZnO 壳层和 ZnO 纳米棒。In 种子被认为是吸引 ZnO 分子蒸气的中心，进一步通过气-液-固机制诱导 ZnO 纳米棒从 Si/ZnO 核壳 NWs 侧向生长。X 射线衍射和高分辨率透射电子显微镜分析表明，ZnO 纳米棒倾向于沿[0001]方向生长。我们表明，由于 ZnO 和 In2O3 结构中的氧空位发射以及 Si NWs 上的纳米晶 Si 的组合，Si/ZnO 核壳 NWs 表现出从 400 到 750nm 的宽可见发射。在核壳 NWs 上直 ZnO 纳米棒的分级生长最终减少了缺陷（绿色）发射并增强了 ZnO 的近带边（紫外线）发射。
