纳米硅薄膜光吸收谱的研究

用恒定光电导法测量了纳米硅(其晶粒尺寸为3-5nm,晶态成分比X_c为45％—50％)薄膜在0.9—2.5eV范围的光吸收谱。分析了在不同光子能量范围可能存在的对光电导作主要贡献的几种光跃迁过程,以及随着X_c的增加,材料由非晶、微晶转变为纳米硅薄膜时光吸收谱的变化。发现纳米硅晶粒之间的界面区(平均厚度约为1nm)中载流子的跃迁及传输过程对整个范围的光吸收谱起主导作用。联系纳米硅的这种特殊结构解释了有关实验结果。关键词：

A STUDY OF OPTICAL ABSORPTION SPECTRA OF NANO-CRYSTALLINE SILICON FILMS

We employed the constant photo-conductivity method (CPM) to measure the optical absorption spectra of nano-crystalline siilicon films (nc-Si :H) in the energy range of 0. 9-2. 5eV. We analysed some possible major optical transition processes resulting from the photo-conductivity at different photon energy range and the variation of optical absorption spectra while the films were transformed from amorphous silicon into microcrystalline silicon and then nano- crystalline silicon films. We found that the carriers' optical transition and transport process at the interfaces between grains play an important role in the optical absorption spectra in the whole energy range. We make use of the novel structure of nc-Si:H films to explain our experimental results.