Photoinduced structural relaxation in chalcogenide glasses

Measurements of residual entropy were performed on irradiated chalcogenide glasses using a modulated differential scanning calorimeter. We show that glass from the GexSe1−x system can undergo extensive structural relaxation under sub-bandgap irradiation. This ability to relax is correlated with the strong/fragile character of the glass-forming system. Fragile glassformers experience larger relaxation as expected from the Kauzmann entropy plot. The temperature dependence of this photorelaxation process is also consistent with entropy relaxation. These measurements demonstrate that the glass configurational entropy decreases under irradiation. This can be regarded as a light activated aging process.