Localization of the Si-H stretch vibration in amorphous silicon

Vibrational transient grating measurements have been performed on the Si-H stretch vibration of amorphous silicon using intense picosecond infrared pulses from a free electron laser. From these data, the vibrational lifetime can be obtained directly, providing a valuable probe of the microscopic structure and dynamics in the vicinity of the Si-H bond. The stretch mode lifetime has been studied as a function of temperature and across the absorption band. Unexpectedly, the Si-H stretch vibration is demonstrated to be highly localized, and the bulk of the vibrational energy is shown to flow directly to bend vibrations, rather than to other stretch states or to host phonons. (C) 1999 American Institute of Physics. [S0003-6951(99)01245-0].