Evidence for the Intermediate Phase in Chalcogenide Glasses

Abstract

Raman scattering and T-modulated Differential Scanning Calorimetry measurements on several families of chalcogenide glasses have been performed. Comprehensive results are now available on the GexSe1−x and SixSe1−x binary glass systems, where rigidity is found to onset in two steps; a second-order transition at xc(l)=0.20 in both binaries from a floppy to an unstressed rigid phase, and a first-order transition at xc(2)=0.26 for Ge-Se,=0.27 for Si-Se binary from an unstressed rigid to a stressed rigid phase. The two transitions (xc(1), xc(2)) define the bounds of an intermediate phase that separates the floppy from the stressed rigid phase. The near absence of the non-reversing heat-flow, ΔHnr, constitutes evidence for the stress-free nature of the backbone of glass compositions in the intermediate phase. Light-induced melting of the intermediate phase in micro-Raman measurements on the Ge-Se glass system has also been observed.