纳米硅薄膜的Raman光谱

通过等离子增强化学气相沉积法 ,制备了本征和掺磷的氢化纳米硅薄膜 (nc- Si:H) ,研究了晶粒尺寸和掺杂浓度对纳米硅薄膜喇曼谱的影响 .结果表明晶粒变小和掺杂浓度增加都使纳米晶粒的 TO模峰位逐渐偏离声子限制模型的计算值 .X射线衍射和高分辨电镜像的结果表明晶粒变小导致硅晶粒应力增加 ,而掺杂使晶粒内部杂质和缺陷增多 ,这些因素破坏了晶粒内晶格的平移对称性 ,进一步减小声子的平均自由程 ,导致实验值偏离理论计算值 .晶格平移对称性的破缺还体现在 ,随晶粒尺寸减小或掺杂浓度增加 ,喇曼谱中 TA、LA振动模的相对散射强度增加 .

Raman Spectra of Nanocrystalline Silicon Films

Using plasma enhanced chemical vapor deposition system, intrinsic hydrogenated nanocrystalline silicon films and P-doped ones have been fabricat ed. The dependence of Raman shift on the grain size and doping concentration has been systemically studied. T he results show that both the decrease in grain size and the increase in doping concentration can make the peak-position of TO band for silicon grains deviate gradually from the value obtained by phonon confinement model. The deviation is attributed to the strain, impurities and defects inside the grains due to the fi nite grain size or doping. In addition, the relative scattering intensities of T A and LA increase when the grain size decreases or the doping concentration incr ease s. The main reason may be that the finite grain size and doping destroy the lat tice translational symmetry, which makes the selection role of the Raman scatter ing relaxed, and therefore increases the scattering possibility of the TA and LA models.