Positronics of radiation-induced effects in chalcogenide glassy semiconductors

Using As2S3 and AsS2 glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models

Peculiarities of Ga and Te incorporation in glassy arsenic selenides

International audienceEffect of simultaneous Ga and Te addition on the structure of As2Se3 glasses is studied using X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS) and Raman techniques. It is shown that most of As, Se and Te atoms build a covalent network according to their main valences. Three-fold coordinated As atoms form pyramidal structural units, which are connected via bridges of two-fold coordinated chalcogen atoms (Se, Te). On the other hand, coordination of Ga in glassy samples is found to be greater than three, as expected from its valence, increasing with Te content. Some of the As atoms appear to be converted into four-fold coordinated state at low Te concentration, while a fraction of Te and, possibly, Se atoms are thought to exist in a singly-coordinated (terminal) state in the vicinity of Ga in the samples with higher Te concentration

On the glass transition temperature Tg against molar volume Vm plotting in arsenoselenide glasses

International audienceDependence of glass transition temperature Tg (K) on overall mean bonding energy E (kJ/mol) in arsenoselenide glass reexamined under per-atom calculations is shown to obey linearized master equation Tg ≅ 418⋅(E–1.13). Compositional variations in Tg against molar volume Vm are plotted for g-AsxSe100- x taken within (0 ≤ x ≤ 65) domain assuming preferential cohesive Van der Waals (VDW) bonding between network-constituting entities. The Tg values are found to vary as inverse-αth power of Vm, attaining distinct values for different networks, in part, 0D-molecular (α=6/3= 2), 1D-chained (α=5/3), 2D-layered (α=4/3), and 3D-spatial (α=3/3=1). These variations originated from macroscopic geometry of VDW interaction are linearized in log-log presentation for networks dominated with chain-like 1D-entities (0 ≤ x<~8) and cross-linked 3D-entities (~8<x<30–33), while demonstrate non-linear behaviour for cross-linked 3D- and layered 2D-entities (30–33 andlt; x andlt; 40), and layered 2D- and molecular 0D-entities (40 andlt; x andlt; 65). Appearance of molecular entities in g-AsxSe100- x (40<x<65) results in self-terminated loop in log–log plotting of Tg(1/Vm) dependence