Peculiarities of Ga and Te incorporation in glassy arsenic selenides

Abstract

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

Nanoscale mechanism of rare‐earth doping in Ga‐codoped glassy As‐Sb selenides

“…Successful resolution of this problem is just based on the possibility of Ga codopants to reveal their metallic behavior being inserted in a covalent‐bonded ChG network. In interaction with chalcogens, the Ga atoms create some polyhedrons, which are, from one side, topologically consistent with principal network‐forming polyhedrons to attain unique cycle‐type arrangement having a large number of character voids, but, from other side, these codopants are able to stabilize some electrical charge misbalance owing to local chalcogen (Se) overcoordination around Ga atoms . Therefore, under transition to g‐Ga 2 (As 0.40 Se 0.60 ) 98 , the GaSe 4/2 tetrahedrons with energetically favorable Ga‐Se bonds appear in a network of corner‐shared trigonal AsSe 3/2 pyramids forming characteristic cycle‐atomic arrangement of g‐As 2 Se 3 (see Figure B).…”

“…In interaction with chalcogens, the Ga atoms create some polyhedrons, which are, from one side, topologically consistent with principal network-forming polyhedrons to attain unique cycle-type arrangement having a large number of character voids, but, from other side, these codopants are able to stabilize some electrical charge misbalance owing to local chalcogen (Se) overcoordination around Ga atoms. 8,10,38 Therefore, under transition to g-Ga 2 (As 0.40 Se 0.60 ) 98 , the GaSe 4/2 tetrahedrons with energetically favorable Ga-Se bonds appear in a network of cornershared trigonal AsSe 3/2 pyramids forming characteristic cycle-atomic arrangement of g-As 2 Se 3 (see Figure 6B). This structure is not disturbed essentially under condition of small amount of Ga codopant added, apart from some homonuclear As-As bonds (red distinguished on Figure 6B), which appear to compensate lack of Se atoms in =As-Se-As= bridges.…”

The influence of Sb on glass‐forming ability of Ga‐containing As2Se3 glasses

“…The normalized micro‐Raman spectra of Ga 2 (As 0.40− x Sb x Se 0.60 ) 98 ChG ( x =0, 0.04, 0.12, 0.20) are shown in Figure . The spectrum for Ga 2 (As 0.40 Se 0.60 ) 98 glass is very similar to one detected for As 40 Se 60 glass without any additional peak which can be attributed to Ga‐based units. The Raman peaks in 200‐270 cm −1 region correspond to stretching modes of pyramidal AsSe 3/2 units (the broad band grouped around 230 cm −1 ).…”

Nanoscale Inhomogeneities Mapping in Ga-Modified Arsenic Selenide Glasses

“…In this case, the mid-IR light can be initiated by emission of excited RE ions (such as Pr 3+ , Er 3+ , Dy 3+ , Tb 3+ ) on different wavelengths, thus creating the remote sources of light [5–8]. From purely implementation point, it is important to achieve a high enough concentration of RE ions in ChG. One of best solutions relies on introducing Ga (or In) into ChG matrix, permitting dissolution of higher ratio of RE dopants [8–13]. However, the Ga additions may essentially restrict glass-forming ability in many ChG systems [8, 11, 13–15] provoking parasitic devitrification processes at a nanoscale through phase separation, crystallite nucleation, growth, and extraction (uncontrolled spontaneous crystallization).…”

“…From purely implementation point, it is important to achieve a high enough concentration of RE ions in ChG. One of best solutions relies on introducing Ga (or In) into ChG matrix, permitting dissolution of higher ratio of RE dopants [8–13]. However, the Ga additions may essentially restrict glass-forming ability in many ChG systems [8, 11, 13–15] provoking parasitic devitrification processes at a nanoscale through phase separation, crystallite nucleation, growth, and extraction (uncontrolled spontaneous crystallization). Thus, it was shown, that in case of glassy As 2 Se 3 it is not possible to introduce more than 3 at.% of Ga without such intrinsic structural decomposition, which essentially influences the ChG functionality [8, 12, 14].…”