Anomalous temperature dependence of photoinduced fluidity in chalcogenide glasses

A temperature-dependent, sub-band-gap, light-scattering study of the vibrational modes of vitreous As2S3 fibers during the photoinduced fluidity effect is reported. The structural changes that give rise to the effect are detected mainly through variations in the degree of polarization of the scattered light. The results show a nonmonotonic behavior in the observed structural changes interpreted as a reduction in the flow ability of the glass a few degrees above room temperature followed by a subsequent increased ability to plastic deformation at higher temperatures, but still well below the glass-transition temperature. Studies on the nonstoichiometric concentration As25S75 at room temperature revealed noticeable differences with arsenic trisulfide. The relation between the illuminating energy and the band gap of the glass has also been investigated. An account for the possible nature of these experimental facts is attempted in terms of the specific structural units constituting the glass structure.