Identifying medium-range structure response on cation- and anion-substitution modification effects in glassy arsenoselenides

Abstract

Medium-range structure responses on cation- and anion-substitution modification effects are recognized in glassy arsenoselenides deviated from As 2 Se 3 stoichiometry due to pnictogen-type Ga co-doping or transition to chalcogen-optimized Se-Te-rich alloys employing X-ray powder diffraction (XRPD) analysis. Straightforward interpretation of the results is developed within modified microcrystalline approach treating amorphous peak-halos in diffraction patterning of these alloys as superposition of the Bragg-diffraction reflexes from quasi-crystalline remnants (inter-planar correlations), supplemented by the Ehrenfest-diffraction reflexes from most prominent inter-molecular/atomic correlations belonging to them. Interplay from intermediate-to extended-range ordering prevails in the medium-range structure response on Ga co-doping in Ga x (As 0.4 Se 0.6 ) 100-x alloys, this effect being in opposite to intrinsic pnictogen-enriching modification trend in transition from As 2 Se 3 to over-stoichiometric As-rich glassy alloys. The same type of medium-range structure response is character for anion-substitution Se-to-Te modification in alloys of Ga 2 (As 0.4 Se 0.6 ) 98-y Te y cut-section, this trend being in accord to intrinsic transition from stoichiometric As 2 Se 3 to under-stoichiometric chalcogen-rich arsenoselenides.