纳米硅薄膜的拉曼谱研究

Raman Study of Nanocrystalline Silicon Films

通过等离子增强化学汽相沉积法 ,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拉曼谱的影响 .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-射线衍射和透射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 ,随晶粒尺雨减小或掺杂浓度增加 ,拉曼谱中 TA,LA振动模的相对散射强度增加 .

Using plasma enhanced chemical vapor deposition system we fabricated intrinsic and P- doped hydrogenated nanocrystalline silicon films.We systematically studied the de- pendence of Raman shift on the grain size and doping concentration. The results show that, both decreasing grain size and increasing doping concentration will 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 greater strain,more impurities and defects inside grains caused by the finite grain size or doping.In addition,the relative scattering intensity of TA and LA increase when the grain size decreases or the doping concentration increases. The main reason may be that the finite grain size and doping destroy the lattice translational symmetry,making the selection role of the Raman scattering relax,and therefore increase the scattering possibility of the TA and LA models.