Electrical switching and topological thresholds in Ge-Te and Si-Te glasses

Abstract

Melt-quenched Ge x Te 100−x glasses and Si x Te 100−x glasses (15 ≤ x ≤ 25) have been found to exhibit memory switching, with threshold fields of the order of 4-11 kV/cm and 6-25 kV/cm, respectively. It is found that the switching voltages of Ge x Te 100−x samples increase linearly with Ge content and the composition dependence of threshold voltage V t shows a marked slope change at x = 20, which has been earlier identified as the rigidity percolation threshold (RPT) of the system. Above the RPT, V t of Ge-Te glasses continues to increase with composition until the boundary of bulk glass formation (x = 28). On the other hand, the switching voltages of Si x Te 100−x glasses increase with x, exhibiting a broad maximum around x = 20 (RPT). The difference in the composition dependence of Si x Te 100−x and Ge x Te 100−x glasses has been understood on the basis of separation between the rigidity percolation threshold and the stoichiometric threshold (CT ST) in these samples. The present results also indicate that the turnaround in the composition dependence of V t and the subsequent minimum observed in the switching voltages of chalcogenide glasses is likely to be due to CT ST and not to the chemical ordering threshold (CT COCRN).

Electrical switching behavior of bulk Si15Te85−xSbx chalcogenide glasses – A study of compositional dependence

“…Telluride glasses also exhibit a clean electrical switching behavior without any fluctuations in the I-V characteristics during the transition to the ON state. The present results indicate that the electrical switching behavior of Si 15 Te 85Àx Sb x glasses is similar to other binary and ternary telluride glasses such as Si-Te [15], As-Si-Te [16], Ge-Te-Si [17], etc. and also thin film amorphous tellurides like Si-Te-Sb [18,19].…”

“…Fig. 6 shows the variation of threshold voltages for the sample Si 15 Te 79 Sb 6 in the temperature ranges of 30-110°C. It can be seen that there is a continuous decrease in the V th with increase in temperature, which is consistent with the decrease in energy barriers for devitrification decrease at high temperatures [34].…”

“…Earlier investigations reveal that binary Si-Te glasses [15] and ternary samples in bulk glassy and amorphous thin film form containing Si including As-Te-Si [16] Ge-Te-Si [17], exhibit electrical switching phenomenon. Further, the feasibility of replacing Ge in Ge-Sb-Te with Si for PCM applications is being explored, due to better properties of Si-Sb-Te glasses [18,19], such as smaller reset current, lower power consumption and a good data retention as compared to the Ge 2 Sb 2 Te 5 [18][19][20][21].…”

Network topological thresholds in gallium doped As–Te glasses – Electrical and thermal investigations

“…Compared to variations in other properties, the effects of network rigidity and topological thresholds on the composition dependence of electrical switching voltages are more universal in nature. In several binary and ternary glassy systems such as Al-Te [10], Ge-Te [11], As-Te [12], Ge-As-Te [13], Al-Ge-Te [14], etc., which exhibit memory switching, the switching voltages are found to increase with the increase in network rigidity. This increase in threshold voltages/fields is expectable, as the reorganization of the glassy network, which is necessary for memory switching, becomes more difficult with increasing network rigidity.…”

Electrical switching and thermal studies on bulk Ge–Te–Bi glasses

“…The composition dependence of threshold/switching voltage in chalcogenide glasses is determined by three main factors, namely the resistivity of the additive elements [33], network connectivity, rigidity [34] and chemical ordering [35]. The addition of more metallic elements usually brings down the switching voltages of chalcogenide glasses; this is also the case in the present Ge 18 Te 82-x Bi x system in which Bi is more metallic compared to Te (ρ Bi = 1.29 × 10 −6 Ω m and ρ Te = 1 × 10 −4 Ω m) and the replacement of Te with Bi leads to the reduction in the threshold voltages (Fig.…”