Temperature dependence of the structures of As2Se3 and AsxS1−x glasses near the glass transition

Abstract

The temperature dependence of the x-ray structure factor has been measured for ${\mathrm{As}}_2$ ${\mathrm{Se}}_3$ and ${\mathrm{As}}_x{\mathrm{S}}_{1-x}$ glasses of compositions $x=0.40,0.33,0.19, \mathrm{and} 0.11$. In all of these glasses, a surprising increase in the first-diffraction-peak intensity was observed with increasing temperature while the second-diffraction-peak intensity decreased. These changes were fully reversible. Measurements have been made above the glass transition temperatures $T_g$ for the ${\mathrm{As}}_x{\mathrm{S}}_{1-x}$ glasses, where the intensity changes continue the behavior seen below $T_g$. It is suggested that these results are consistent with the existence of local layering in these glasses and are suggestive of a mechanism for the viscosity decrease above $T_g$. In addition, for the ${\mathrm{As}}_x{\mathrm{S}}_{1-x}$ glasses, plots of the intensities normalized to those at $T_g$ vs $\frac{T}{T_g}$ gave a universal temperature-dependence behavior for all $x$ up to $1.2T_g$.