Electrical switching and thermal studies on Ge22Te78−xIx chalcohalide glasses: The effect of iodine on network-topology

Investigations on the electrical switching behavior and thermal studies using Alternating Differential Scanning Calorimetry have been undertaken on bulk, melt-quenched Ge22Te78−xIx (3≤x≤10) chalcohalide glasses. All the glasses studied have been found to exhibit memory-type electrical switching. The threshold voltages of Ge22Te78−xIx glasses have been found to increase with the addition of iodine and the composition dependence of threshold voltages of Ge22Te78−xIx glasses exhibits a cusp at 5 at.% of iodine. Also, the variation with composition of the glass transition temperature (Tg) of Ge22Te78−xIx glasses, exhibits a broad hump around this composition. Based on the present results, the composition x=5 has been identified as the inverse rigidity percolation threshold at which Ge22Te78−xIx glassy system exhibits a change from a stressed rigid amorphous solid to a flexible polymeric glass. Further, a sharp minimum is seen in the composition dependence of non-reversing enthalpy (ΔHnr) of Ge22Te78−xIx glasses at x=5, which is suggestive of a thermally reversing window at this composition.