Fluorine-induced suppression of disorder effects of carbon in the hydrogenated amorphous silicon-carbon alloy thin films

Abstract

We report here the Raman scattering studies of modifications in the structural disorder due to fluorine incorporation in the hydrogenated amorphous silicon-carbon (a-Si1−xCx:H) alloys. The structural disorder in the unfluorinated a-Si1−xCx:H alloys has been observed to increase continuously with the increasing carbon content, whereas the incorporation of fluorine appears to substantially suppress disordering effects of carbon, irrespective of its concentration in the alloy. Additional support for this suppression of disorder is sought from the enhancement of optical band gap after fluorine incorporation in these alloys. The fluorine-induced suppression of disorder is attributed to the increase in the fraction of sp3 bonded carbon in the fluorinated alloys compared to that of the unfluorinated alloys. The fluorine as well as hydrogen appear to have a preferential attachment with the carbon atoms that tend to form higher hydride and fluoride species which in turn constrain the carbon atoms to form sp3 hybridized C-C or Si-C bonding in the alloys.