The boson peak related correlations in glasses As–S–Ge from the intermediate phase

Abstract

The low-frequency Raman scattering in nonstoichiometric AsS3–GeS4 glasses from the intermediate phase of As–S–Ge ternary has been studied together with stoichiometric As2S3 and GeS2. The study was addressed to clarify to what extent the Boson peak correlates with the first sharp diffraction peak of the XRD patterns, with respect to stoichiometry and structural transformations caused by glass composition change (STGC). Various mechanisms of boson peak formation in glasses enriched with arsenic and germanium have been identified. It is shown that in arsenic-enriched glasses, regardless of stoichiometry, the boson peak is due to the peak of excess of the density of vibrational states (e-VDOS) over the Debye ones. On the other hand, in Ge-enriched glasses, Debye-type oscillations become dominant, suggesting a change in the coupling constant. Since AsS3–GeS4 glasses topologically belong to the intermediate phase, special attention was paid to the influence of STGC on e-VDOS. A combined analysis of the Boson peak and previously studied high-frequency Raman spectra revealed that the STGC may be the possible cause of the decrease in the e-VDOS peak and its red shift.