氢化纳米硅薄膜中氢的键合特征及其能带结构分析

对氢化纳米硅薄膜中氢的键合特征和薄膜能带结构之间的关系进行了研究.所用样品采用螺 旋波等离子体化学气相沉积技术制备，利用Raman散射、红外吸收和光学吸收技术对薄膜的 微观结构、氢的键合特征以及能带结构特性进行了分析.Raman结果显示不同衬底温度下所生 长薄膜的微观结构存在显著差异，从非晶硅到纳米晶硅转化的衬底温度阈值为200℃.薄膜中 氢的键合特征与薄膜的能带结构密切相关.氢化非晶硅薄膜具有较高的氢含量，因键合氢引 起的价带化学位移和低衬底温度决定的结构无序性，使薄膜呈现较大的光学带隙和带尾宽度 .升 关键词： 氢化纳米硅 螺旋波等离子体 能带结构

Hydrogen bonding configurations and energy band structures of hydrogenated nanocrystalline silicon films

The correlation between the hydrogen bonding configurations and the energy band structures of hydrogenated nanocrystalline (NC) silicon films has been investiga ted. The samples were prepared by helicon wave plasma chemical vapor deposition technique. Raman scattering, infrared absorption and optical absorption measurem ents were used to analyze the microstructure, hydrogen bonding configurations an d energy band structures of the deposited films. Raman results indicate that dis tinct different structures appear in films deposited at various substrate temper atures and there is a threshold at about 200℃ for the amorphous silicon to be t ransformed to the NC phase. The energy band structures of the films are closely related to their hydrogen bonding configurations. The chemical shift of the vala nce band to the lower state induced by high hydrogen content and the structural disorder related to low substrate temperature makes the films have wide band gap s and large band tail widths. With increasing the substrate temperature, the dec rease trend of optical band and tail width is mainly related to the enrichment o f the hydrogen located in the grain boundary, which perform the function of term inating the dandling bonds at NC silicon grain surface. Further increasing the s ubstrate temperature broadens the band tail width of the films because the hydro gen content is too low to passivate the dangling bonds at the NC silicon grain s urface.