Ultrafast infrared experiments on Si-H vibrations in a-Si : H

Ultrafast infrared experiments in a-Si:H are presented on Si-H vibrations g rown by plasma enhanced chemical vapor deposition and hot-wire techniques, in the temperature regime between 10 and 300 K. Non-exponential population decay of the stretching mode is observed, with a mean time constant ranging from 30 to 100 ps. At low temperatures (similar to 15 K) the phase relaxat ion is limited by the population decay, but speeds up at high temperatures and becomes a single exponential. The phase relaxation depends on the power of the laser. We discuss the results in terms of a model in which the stre tching mode is localized and decays into three bending modes and one TA. ph onon. (C) 2000 Elsevier Science B.V. All rights reserved.