Fictive Temperature Dependence of Arsenic Trisulfide Glass Molecular Structure Probed by Nuclear and Optical Spectroscopy

Structure and physical properties of amorphous chalcogenides depend on the method and condition of preparation. We demonstrated that this is even true for chalcogenides with excellent glass forming tendency, such as As_2 S_3. In this work we studied the structure of an overconstrained bulk glass (GeS _2 and GeSe_2) and of an optimally constrained bulk glass (As_2 S_3 and As_2 Se_3) as a function of quench temperature T_{rm q} in the range 500^circC < T_{rm q} < 1000^circC. Mossbauer ^{119}Sn absorption spectroscopy was used to probe cation site in GeS_2 and GeSe_2 . Mossbauer ^{125}Te absorption and ^{129}I emission spectroscopies were used to probe the anion site chemistry in As_2S_3 and As_2Se_3 . Evaluation of spectroscopic results gave us following outcome. With increasing T_{rm q} both, GeS_2 and GeSe_2 undergo a gradual phase separation, the two cluster network will be transformed into four cluster network. This network fragmentation occurs at T _{rm q} = 850^ circC for GeS_2, and at T_{rm q} = 1050 C for GeSe_2. Completely different T_{rm q} induced structural changes are observed for the optimally constrained network of As_2S_3 . Here the network chemical order remains unchanged for the melt-quenched glass (T_{rm q} < 800^circC). Once the glass is prepared by vapor-quenching (T_{ rm q} > 800^circC) its network undergoes gradual polymerization with T_ {rm q}. At T_{ rm q} ~eq 1200^circC we predict a MCN --> CRN transformation. This result is supported by optical absorption measurements.