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

Abstract

Abstract. Local atomic structure of Ge x As 40x S 60 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 -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 Е 1 . 1  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 S As  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 As 2 S 3 chalcogenide glass and similar materials.

Radiation-induced optical darkening and oxidation effects in As2S3 glass

“…As noted, the As-enriched Ge-As-S chalcogenide glasses, not showing the white oxidized layer upon radiation due to decomposition-oxidation reactions [8][9][10][11][12][13], can be selected as better candidates for this purpose. As shown in [15], the XRD study of -irradiated/annealed gGe 16 As 24 S 60 , which corresponds to (As 2 S 3 ) 0.6 (Ge 2 S 3 ) 0.4 alloy, with a dominant structure based on AsS 3/2 pyramids likely to g-As 2 S 3 [25], allows plausibly detecting the radiation-structural changes, including the FSDP-related ones, in the As-S sub-system of chalcogenide glasses. Finally, from the positive point of view, the radiation-induced oxidation observed could be considered as protection procedure to be used in practice.…”

“…In this case, the As-enriched glasses in chalcogenide glassy systems, not showing oxidized layer upon radiation and with structure mainly built by AsS 3/2 pyramids likely to g-As 2 S 3 , can be chosen as better candidates for structural studies by XRD in respect to the FSDP-related correlations, first of all. For instance, the investigation of radiation/annealing-induced structural changes in Ge x As 40-x S 60 glasses (x = 16, 24, 32, 36), which can be also presented as (As 2 S 3 ) y (Ge 2 S 3 ) 1-y non-stoichiometric system (y = 0.6, 0.4, 0.2, 0.1), using high-energy synchrotron XRD is found to be quite informative regarding the FSDPrelated correlations in the As-S sub-system [15]. Namely, the radiation-induced FSDP changes mainly occur in the As-enriched glass composition (x = 16) to be in a good agreement with the photoinduced FSDP changes in the g-As 2 S 3 bulk samples reported by Tanaka [4,5].…”

Long-term radiation-induced optical darkening effects in chalcogenide glasses

“…Indeed, on the one hand, the established for As-S based glasses the long-term radiation-induced structural changes in DBAL data [2,11,14], when the first sharp diffraction peak (FSDP) becomes weaker and broader after γ-irradiation [2,12], have been interpreted within the non-defective distortion model. Since the FSDP originates as a signature of the medium-range order (MRO) structure within the range 5…20 Å in covalent glasses (for review, see [18]), which is commonly accepted by many researchers in literature, the FSDP weakening and broadening means the decrease in the MRO structural correlation length and, consequently, the rise of disordering on the MRO scale.…”

“…It may also indicate that a backward measuring chronology mentioned by the authors [10], it is not necessary to be performed, being although useful to make in situ experiment, as the radiation-induced optical darkening effects in chalcogenide glasses are stable in time, and corresponding radiation-induced structural changes can be correctly investigated with a long-time interval. In this respect, the long-term radiation-induced structural changes examined in the works [2,[11][12][13][14] are very important in view of practical applications of chalcogenide glasses. In particular, the long-term radiation-induced effects demonstrate the possibilities for development of innovative chalcogenide glass based longterm dosimeter systems with stable and controlled parameters.…”

On the origin of radiation-induced metastability in vitreous chalcogenide semiconductors: The role of intrinsic and impurity-related destruction-polymerization transformations

“…[10], appears as an artifact of many inconclusive findings on their eventual nature. Thus, for example, the broadening of the first sharp diffraction peak (FSDP) in v-As 2 S 3 (which, by overall opinion, is a manifestation of medium-range ordering at the atomistic length scales ranging from a few to 10 Å [11][12][13]) due to radiationinduced oxidation [14] was mistakenly ascribed to own structural changes [15], they being imagined as fully identical to reversible photoexpansion [16,17]. An obvious difference in the origin of photo-and radiationinduced metastability was thus ignored at all.…”