Reversibility Window, Aging, and Nanoscale Phase Separation in GexAsxS1-2x Bulk Alloy Glasses

The non-reversing enthalpy near Tg, DHnr, in bulk GexAsxS1-2x glasses is found to display a global minimum (~0) in the 0.11 < x < 0.15 range, the reversibility window. Furthermore, the DHnr term is found to age for glass compositions both below (x < 0.11) and above (x > 0.15) the window but not in the window. Glass compositions in the window are rigid but stress-free, those below the window are floppy, and those above the window are stressed-rigid. Raman scattering shows floppy and stressed rigid networks to consist in part of monomers. The latter aspect of structure narrows the width of the reversibility window and suppresses in part aging effects observed outside the window in contrast to those in the fully polymerized selenide counterparts.