Non-isothermal crystallization kinetics and memory switching properties of Tl-Se-Ge-Sb chalcogenide semiconductor alloy for thermally stable phase change memory applications

Abstract

Quaternary (Tl20Se70Ge10)0.85Sb0.15 chalcogenide glass was synthesized using melt-quenching and thermal evaporation techniques for bulk and thin film samples, and its amorphous character was confirmed by XRD. Based on different models of non-isothermal crystallization kinetics, the average values of the glass transition E ̅ g and the crystallization E ̅ c activation energies are 121.33 and 82.94 kJ mol−1, respectively. The crystallization mechanism in the examined composition is 2D nucleation growth, according to Avrami exponent n . Thermal parameters of the studied quaternary glass, like fragility F g , fluctuation free volume F FV , reduced glass transition temperature T rg , thermal stability SP and glass formation ability GFA were investigated and indicated that the (Tl20Se70Ge10)0.85Sb0.15 ChG exhibits a good ability of glass formation and thermal stability. The obtained results of the dc electrical conductivity σ dc are found to increase with temperature and decrease with film thickness. The electrical conduction activation energy ∆ E σ (0.583 ± 0.004 eV) is thickness independent and the predominant conduction mechanism is the hopping of charge carriers in the band tail localized states. The ( I – V ) curves of (Tl20Se70Ge10)0.85Sb0.15 chalcogenide glass film samples were analyzed and shown to be appropriate for a memory switch. The mean value of the threshold voltage V ̅ th decreases exponentially as temperature increases, whereas it increases linearly as film thickness increases. The values of threshold voltage ε th and threshold resistance ∆ E R activation energies are 0.282 ± 0.003 and 0.521 ± 0.004 eV, respectively. The obtained switching characteristics data were discussed in view of the electrothermal model motivated by current channel Joule heating. These findings highlight the suitability of the investigated composition for various optoelectronic applications, such as memory switching devices, optical data storage, phase-change memories and optical fibres sensing devices.