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 pu lses from a free electron laser. From these data, the vibrational lifetime can be obtained directly, providing a valuable probe of the microscopic str ucture and dynamics in the vicinity of the Si-H bond. The stretch mode life time has been studied as a function of temperature and across the absorptio n band. Unexpectedly, the Si-H stretch vibration is demonstrated to be high ly localized, and the bulk of the vibrational energy is shown to flow direc tly to bend vibrations, rather than to other stretch states or to host phon ons. (C) 1999 American Institute of Physics. [S0003-6951(99)01245-0].