Raman scattering in glasses at high temperature: the Boson peak and structural relaxation kinetics in glasses

Inelastic light scattering as a function of temperature was carried out on various halide glasses. In their low frequency Raman spectra, all glasses show a broad feature around 50 cm(-1), the so-called Boson peak. This Boson peak is associated with the existence of an intermediate range order in the glass. The Boson peak is due to an increase in the vibrational density of state, over the Debye value, caused by localized excitations. The low frequency Raman scattering containing this dominant spectral line (Boson peak) is interpreted in its relation to the amplitude and extent of the density fluctuations in glasses. The glasses considered in this study are fragile glass formers and the measurements extend from room temperature to the glass transition region. The spectral form of the Boson peak is the same for different glasses and no strong dependence on their respective chemical compositions is observed. The degree and range of disorder in the glasses is obtained in a quantitative sense from the behavior of the Boson peaks with temperature and compared to Rayleigh-Brillouin scattering data on the same glasses. (C) 1997 Elsevier Science B.V.