【摘要】 利用两种不同激发波长进行 Ram an测量 ,研究了低碳含量 a- Si1 - x Cx∶ H (～ <2 0 at.% )薄膜的结构特征 .采用 6 47.1nm激发时 ,由于激发光能量接近于各样品的光学带隙 ,因而在样品中具有较大的穿透深度 ;而采用488nm激发时 ,激发光被样品表面强烈吸收 .探测深度的变化造成了两种激发下 Raman谱出现较大的差异 .实验结果表明样品体内存在硅团簇结构 ,样品的自由表面存在一层高浓度的缺陷层 .这两种空间的不均匀性造成了高能激发时 Raman谱的 TO模频率和半高宽比低能激发时有大的红移和展宽 .以上结果证明不同激发波长将造成Ram an测量结果的差异 .更多还原

【Abstract】 The network disorder of a-Si_ 1-xC_x∶H films,with carbon concentration below 20at% has been studied by means of Raman spectroscopy.Two different radiations are employed:one is Kr+ 6471nm,which is weakly absorbed,with the corresponding energy nearly the same as the optical gaps of these materials;the other is Ar+ 488nm that is strongly absorbed at the free surface,whose corresponding energy is higher than the optical gaps of the materials.Owing to the variations of probed depth attained by two excitation radiations a significant difference is observed in the Raman spectra,which indicates the existence of two kinds of spatially inhomogeneities:a highly disordered thin layer near free surface and inhomogeneities in the bulk.When excited with strongly absorbed radiation,the frequency and width of TO mode have a relatively large redshift and broadening compared with the weakly absorbed one.The above results indicate that different radiation may lead to different Raman results.更多还原