Dynamics of Si-H vibrations in an amorphous environment

We present results of the first Vibrational photon-echo, transient-grating, and temperature dependent transient- bleaching experiments on a-Si:H. Usin g these techniques, and the infrared Light of a free electron laser, the vi brational population decay and phase relaxation of the Si-H stretching mode were investigated. Careful analysis of the data indicates that the vibrati onal energy relaxes directly into SI-H bending modes and Si phonons, with a distribution of rates determined by the amorphous host. Conversely, the pu re dephasing appears to be single exponential, and can be modeled by dephas ing via two-phonon interactions.