Abstract
AbstractThe method of annihilating positrons in positron annihilation lifetime measuring mode is applied to study mechanism of rare‐earth doping in Ga‐codoped arsenic selenide As2Se3 glass modified with Sb. The atomic‐deficient structure of parent As2Se3 glass is imagined as containing positron‐trapping sites in the form of free‐volume voids within cycle‐type arrangement of corner‐sharing trigonal AsSe3/2 pyramids, composed of atomic‐accessible geometrical holes arrested by surrounding atomic‐inaccessible Se‐based bond‐free solid angles. The Ga codoping in As2Se3 glass causes gradual decrease in trapping rate and fraction of trapped positrons due to agglomeration of free‐volume voids. Partial As‐to‐Sb replacement in Ga‐codoped As‐Se glasses leads to better stability against crystallization processes and possibility to further rare‐earth doping without principal changes in the type of positron‐trapping defects. Effect of 500 wppm of Pr3+ in Ga2(As0.28Sb0.12Se0.60)98 glass is explained in terms of competitive contribution of changed occupancy sites in Ga‐modified glassy network available for rare‐earth ions and annihilating positrons.
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