Raman scattering in As–Se–S and As–Se–Te Chalcogenide vitreous semiconductors

Chalcogenide vitreous semiconductors of As–Se–S and As–Se–Te compositions are synthesized, with thin films produced by thermal evaporation in vacuum. X-ray phase analysis and Raman spectroscopy are used to confirm their amorphous state and examine their structural specific features. It is shown that the matrices of both materials have a network-chain structure with covalent bonds between As, Se, S, and Te atoms. Structural units of the type of AsSe$_3$ and AsS$_3$ pyramids, AsSe$_{3/2}$ bipyramids, and $\alpha(\beta)$-As$_4$S$_4$ molecules exist in the As–Se–S matrix, and AsSe$_3$, AsSe$_{3/2}$, As$_2$Se$_3$, and As$_2$Te$_3$ units, in As–Se–Te. The vibrational modes of Se–Se, Te–Te, As–As, As–S, Se–As–Se, As–Se–As, Se–As–S, Se–As–Te, and Se–Te bonds constituting both separate molecules and amorphous matrices are determined.