Spectral dependence of vibrational lifetime of Si–H stretching band in a-Si:H

Abstract Si–H stretching vibration in a-Si:H is sensitive to its local environment, because of its strongly localized nature. As a help to clarify microscopic structural differences around Si–H bonds in relation to the role of hydrogen in structural instability, we have proposed a convenient method for evaluating the relative spectral dependence of the lifetime of a localized vibrational mode. By analyzing relaxation of an excited vibrational population, an equation can be derived, indicating that the vibrational lifetime at an energy, hν, is simply proportional to [ΔE(hν)/E(hν)]/ν4, where ΔE(hν) and E(hν) are spectra of modulated thermal radiation induced by a weak thermal modulation and of emissive power in thermal equilibrium, respectively. The method is applied to several undoped a-Si:H films.