Raman and photoluminescence properties of hydrogenated amorphous silicon carbide alloys with low carbide concentration

Abstract

The network disorder of a-Si 1-x C x :H films containing carbon concentrations below 20at.% has been studied by means of Raman spectroscopy and photoluminescence measurements (PL). Two different radiations were employed to excite these materials, one is nearly the same as the optical gaps of these materials and weakly absorbed (647.1nm), another is higher than the optical gaps of these materials and strongly absorbed (488nm). The variations in probed depth together with the significant differences observed in the Raman spectra and PL spectra indicate the existence of two kinds of spatially inhomogeneities: a highly disordered thin layer near free surface and gap fluctuations due to spatial variations of compositions in the bulk. When excited with strongly absorbed radiation, the frequency and width of TO mode have a large redshift and broadening relatively to the weakly absorbed radiation, while the position and width of PL peak have a blue shift and broadening. The above results indicate that different radiations may lead to different Raman and PL results.