Abstract
We have used the cluster-Bethe-lattice method to study the vibrational local modes of a-Si:(H, C) alloys. The local mode around 780 cm-1 could be assigned to both the Si-C vibrational mode and the wagging/rocking mode of the SiCH3 group. We have studied the variation of the Si-C vibrational modes in relation to the structural change upon annealing. The calculated results are in agreement with the infrared absorption spectra.