Electrical switching studies on Ge–Te–Tl chalcogenide glasses: Effect of thallium on the composition dependence of switching voltages

Bulk Ge17Te83−xTlx glasses (0 ≤ x ≤ 13), have been found to exhibit memory type electrical switching. The switching voltages (also known as threshold voltage — Vth) of Ge17Te83−xTlx glasses are found to decrease with increasing thallium content. The rate of decrease of Vth is greater at lower concentrations and Vth falls at a slower rate for higher thallium concentrations (x ≥ 6).The addition of thallium to the Ge–Te network fragments the covalent network and introduces ionic nature to it; the reduction in network connectivity leads to the decrease in switching voltages with thallium content. The decrease in the glass transition temperatures of Ge17Te83−xTlx glasses with increasing thallium concentration supports the idea of decrease in network connectivity with Tl addition. The more metallic nature of Tl also contributes to the observed reduction in the switching voltages of Ge17Te83−xTlx glasses with Tl content.Further, there is an interesting correlation seen between the threshold voltage Vth and the average bond energy, as a function of Tl content. In addition, the switching voltages of Ge17Te83−xTlx glasses have been found to decrease with sample thickness almost linearly. The set–reset studies indicate that the Ge17Te81Tl2 sample can be switched for more than 10 cycles, whereas other glasses could not be reset beyond two switching cycles.

Research Highlights► Electrical switching studies have been undertaken on Ge17Te83-xTlx glasses with 0≤x≤13. ► All the glasses are found to exhibit memory type switching. ► Switching voltages decrease with increasing thallium. ► The observed decrease is attributed to the ionic nature and fragmentation effect of thallium. ► Variation of switching voltage and the average bond energy are correlated.