Picosecond Infrared Transient Grating and VibrationalEcho Spectroscopy of Deuterated Amorphous SiliconThin Films

摘要

Utilising the infrared output of a free electron laser (FEL), wernhave made transient grating measurements of the temperature dependentrnanharmonic decay rate of Si-D stretch vibrations in deuterated amorphousrnsilicon. Unlike Si-H vibrations, it is found that the excited deuteriumrnmode relaxed with a single exponential decay rate into collective modes ofrnthe host, bypassing the local bending modes. Vibrational echornmeasurements suggest that phase coherence is lost via elastic phononrnscattering with excitation (but not temperature) dependent contributionsrnfrom non-equilibrium phonons.