Positron annihilation in point defects of the glassy As-Se system

Nanovolume positron traps in glassy-like As2Se3

“…Contrary to the previous interpretation of Alekseeva et al [3][4][5], these results were described in terms of saturated positron trapping in extended free-volume defects. However, it was non-ambiguously adopted a fully identical origin for vacancy-type positron traps in chalcogenide crystals and glasses, despite a number of well-known significant differences between these solids.…”

“…Firstly, this ChG was carefully studied by Alekseeva et al in the end of the 70s [3][4][5], the investigated gAs 2 Se 3 samples being prepared in two different thermodynamic modifications. Despite close values of positron lifetimes for both modifications (s 1 % 0.20-0.22 ns and s 2 % 0.36-0.37 ns), the samples prepared with water-ice quenching from 600°C demonstrates the larger I 2 intensity for long PAL component.…”

“…A great number of experimental results on PAL characteristics of chalcogenide glasses (ChG), representing themselves as chemical compounds of IV-V-group elements with chalcogen atoms (S, Se, Te) prepared by conventional melt-quenching method [1], has been accumulated since the 1970s [2][3][4][5][6]. Systemising this data set, one can observe an essential discrepancy for ChG (even of the same chemical compositions) obtained in different research centers.…”

Free-volume correlations in positron-sensitive annihilation modes in chalcogenide vitreous semiconductors: on the path from illusions towards realistic physical description

“…With respect to As-Se glasses that were most studied by PALS in that time due to earlier experimental works by V.P. Shantarovich with co-authors [34,35], the bulk and defect-related positron lifetimes were calculated by approximating an orthorhombic structure for monoclinic c-As 2 Se 3 at the basis of Puska's model [31][32][33]. These lifetimes occur to be 0.240 ns for nontrapped positron annihilation in defect-free bulk cAs 2 Se 3 , while in defected crystal they reached essentially higher values 0.262, 0.274, 0.316 and 0.368 ns for single As and Se vacancies, As-Se divacancy and As-Se 3 quadruple vacancy, respectively.…”

“…(1) for similar ChVS characterized by the same type of positron traps. We performed this calibration procedure on the basis of known experimental positron trapping modes [3,4,7,8,34,35] and void radii calculated in respect to Eq. (4) for 13 chalcogen-enriched compositions of   x 100 x Se S As -g  (see Table 2).…”