非晶微晶过渡区域硅薄膜的微区喇曼散射研究

Micro-Raman study on hydrogenated protocrystalline silicon films

通过改变氢气对硅烷气体的稀释程度 ,并保持其他的沉积参量不变 ,用等离子体增强化学气相沉积 (PECVD)方法成功地制备出处于非晶 微晶相变过渡区域的硅薄膜样品 .测量了样品的室温光电导和暗电导 ,样品的光电性能优越 ,在 5 0mW·cm- 2 的白光照射下 ,光电导和暗电导的比值达到 10 6 .在室温下用微区喇曼谱研究了薄膜的微结构特性 ,用高斯函数对喇曼谱进行了拟合分析 .结果表明 ,在我们的样品制备条件下 ,当H2 和SiH4 的流量比R较小时 ,样品表现出典型的非晶硅薄膜的结构特性 ;随流量比R的增大 ,薄膜表现出两相结构 ,其中的微晶成分随氢稀释比的增大逐渐增多 ;用量子尺寸效应估算了两个高氢稀释样品 (R >5 0 )中微晶粒的平均尺寸大小为 2 4nm左右 ;

Good quality hydrogenated protocrystalline silicon films were successfully prepared by radio frequency plasma enhanced chemical vapor deposition (PECVD) with various hydrogen dilution ratios (R = ([H-2]/[SiH4]) from 10 to 100). The photosensitivity of the films is up to 10(6) under the light intensity of 50mW.cm(-2). The microstructure of the films was studied by micro-region Raman scattering spectra at room temperature. The deconvolution of the Raman spectra by Gaussion functions shows that the films deposited under low hydrogen dilution ratios (R < 33) exhibit typical amorphous properties, while the films deposited under high hydrogen dilution ratios (R > 50) possess a diphasic structure, with increasing crystalline volume fraction with R. The size of the crystallites in the diphasic films is about 2.4 mm, which was deduced from the phonon confinement model. The intermediate range order of the silicon film increases with increasing hydrogen dilution ratio.