Temperature dependent vibrational spectra and bond dynamics in hydrogenated amorphous silicon

We present the results of extensive modeling of hydrogenated amorphous silicon (a-Si:H) by combined ab initio molecular dynamics, an improved signal processing technique, and computer visualization, focusing on vibrational properties of a-Si:H. By comparing the theoretical and experimental vibrational spectra we correlate the hydrogen and silicon dynamics with the structural stability, bonding geometry, and diffusion in the a-Si:H material. Microscopic characteristics that cannot be obtained by other techniques, namely, hydrogen migration, bond switching, and silicon dangling bond passivation, are extracted from the atomic dynamics. We also demonstrate that this method offers the possibility of accessing other important macroscopic characteristics of a-Si:H and its stability in general. The approach we have developed can be used as well to model all aspects of a-Si:H dynamics, including the detrimental Staebler-Wronski effect. (c) 2008 American Institute of Physics.