Composition dependent electrical switching in $Ge_xSe_{35-x}Te_{65} (18 \leq x \leq 25)$ glasses - the influence of network rigidity and thermal properties

Electrical switching investigations and supportive thermal studies have been undertaken on semiconducting chalcogenide $Ge_xSe_{35-x}Te_{65} (18 \leq x \leq 25)$ glasses prepared in bulk form. An interesting composition dependent change (memory to threshold) has been observed in the switching behavior of these glasses across the stiffness/rigidity percolation threshold (RPT) at x = 20 (<r> = 2.40). Also, the rigid $Ge_xSe_{35-x}Te_{65}$ glasses are found to retain the threshold behavior for hundreds of switching cycles. Further, the switching voltage of $Ge_xSe_{35-x}Te_{65}$ glasses has been found to exhibit an abrupt increase at the RPT. \ud Alternating Differential Scanning Calorimetric studies indicate that the $Ge_xSe_{35-x}Te_{65}$ glasses with higher tellurium concentrations exhibit two crystallization exotherms, which coalesce at the composition x = 20.5 (average coordination <r> = 2.41), which also marks the beginning of melting endotherms. The relatively low crystallization temperature $(T_{c1})$, along with the floppy structural network aids easy phase change in $Ge_xSe_{35-x}Te_{65}$ glasses with x < 20, causing them to exhibit memory switching. The moderately higher crystallization temperature $(300-330^o C)$ and the stabilizing influence of network connectivity & rigidity are plausibly responsible for the threshold behavior seen in the rigid $Ge_xSe_{35-x}Te_{65}$ glasses