相变区硅薄膜拉曼和红外光谱分析

采用等离子体增强化学气相沉积(PECVD)技术制备了一系列不同氢稀释率下的硅薄膜，采用拉曼散射光谱和傅里叶红外光谱技术研究了非晶/微晶相变区硅薄膜的微观结构变化，将次晶结构(paracrystalline structure)引入到非晶/微晶相变区硅薄膜结构中，提出了次晶粒体积分数(f_p)，用来表征硅薄膜中程有序程度。结果表明，氢稀释率的提高导致硅薄膜经历了从非晶硅到微晶硅的相变过程，在相变区靠近非晶相的一侧，硅薄膜表现出氢含量高、结构致密和中程有序度高等特性，氢在薄膜的生长中主要起到表面钝化作用。在相变区靠近微晶相的一侧，硅薄膜具有氢含量低、晶化率高和界面体积分数小等特性，揭示了氢的刻蚀作用主控了薄膜生长过程。采用扫描电子显微镜对样品薄膜的表面形貌进行分析，验证了拉曼散射光谱和傅里叶红外光谱的分析结果。非晶/微晶相变区尤其是相变区边缘硅薄膜结构特性优良，在太阳能电池应用中适合用作硅基薄膜电池本征层。

Raman and IR Study on Silicon Films at Transition Regime

A series of silicon films at transition regime from amorphous to microcrystalline phase with different hydrogen dilution ratios were fabricated by the plasma-enhanced chemical vapor deposition (PECVD) technique, and the microstructural properties of the films at transition regime from amorphous to microcrystalline phase were studied using Raman scattering and Fourier transform infrared spectroscopy. The paracrystalline structure was used to elucidate the microstructure of silicon films at transition regime from amorphous to microcrystalline phase. The paracrystalline fraction (fp) as a signature of intermediate range order for the silicon films was proposed. The results indicated that the transition from amorphous to microcrystalline phase took place with the increase of hydrogen dilution. Silicon film grown just below transition edge was characterized by high hydrogen content, compact structure and enhanced medium range order, and hydrogen mainly passivated the surface of the film. Silicon film grown just above transition edge was characterized by low hydrogen content, high crystalline fraction and low interface phase, and hydrogen etching played an important role during film growth. The microstructure topography detected by scanning electron microscope verified the results from Raman scattering and Fourier transform infrared spectra. Silicon films had good microstructural properties at transition regime from amorphous to microcrystalline phase, especially around transition edge and were available as intrinsic layer for the thin film solar cells.