Radiation/annealing-induced structural changes in GexAs₄₀-xS₆₀ glasses as revealed from high-energy synchrotron X-ray diffraction measurements

Abstract

Local atomic structure of GexAs₄₀-xS₆₀ glasses (x = 16, 24, 32, and 36) has been investigated in the -irradiated (2.41 MGy dose) and annealed after irradiation states by using the high-energy synchrotron X-ray diffraction technique. The accumulated dose of 2.41 MGy is chosen to be close to the known in literature focal point (~2.0 MGy) for the system tested, at which the y-irradiation-induced optical (darkening) effect does not depend on the composition. It is established that the first sharp diffraction peak (FSDP) is located at around 1.1 Е - in the structure factors S(Q) of all the alloys studied. The FSDP position is found to be constant on radiation/annealing treatment, but the intensity of the FSDP reveals changes under irradiation/annealing only for the compositions with x = 16 and 24. The radiation/annealing-induced changes are also observed on the pair distribution functions in the first and second coordination shells for these compounds. Practically invisible effects on the FSDP and pair distribution functions are found for the alloys with x = 32 and 36. The radiation/annealing-induced structural changes detected mainly in the As - S sub-system of the glasses examined are well explainable within the Tanaka approach for interpretation of the photo-induced structural changes and related phenomena in As₂S₃ chalcogenide glass and similar materials