Ultrafast spectroscopy of localised vibrational modes in amorphous silicon using a free electron laser

Ultrafast vibrational relaxation of localised modes associated with hydrogen, deuterium and oxygen in amorphous silicon based alloys are discussed. The availability of internal defect vibrations to act as accepting modes is discovered to be a crucial factor in the population decay dynamics. Phase relaxation is shown to have both a temperature dependent component due to elastic phonon scattering as well as an excitation dependence contributed by non-equilibrium phonons. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.