Investigation of thermal and electrical properties of Sn and Al incorporated Se–Te chalcogenide glasses for phase change memory applications

In this work structural, thermal and electrical properties of multi-component (Se₈₅Te₁₅)₉₅Sn_xAl_y chalcogenide glasses synthesized by melt quenching technique are reported. Results obtained from thermal and electrical characterizations are used to anticipate the electrical phase change behavior of prepared glasses and significance of Al and Sn incorporation in Se–Te glass for phase change memory device applications has been discussed. Thermal investigation of prepared alloys by DSC at heating rates of 5, 10, 15 and 20 K/min revealed a stepwise increase in characteristic temperatures (T_g, T_c, T_p and T_m). However, a decrease in characteristic temperature also accompanied by a decrease in the value of activation energy of crystallization (E_c) in response to addition of metallic impurities in the alloys has been witnessed. Estimated value of Avrami index and results revealed by XRD analysis suggests nucleation only at the surface of alloys Se₈₅Te₁₅ and (Se₈₅Te₁₅)₉₅Sn₅ while a volumetric crystal growth in (Se₈₅Te₁₅)₉₅Sn_2.5Al_2.5 and (Se₈₅Te₁₅)₉₅Al₅ has been observed. Addition of Al and Sn resulted in the enhanced AC and DC conductivity of alloys and a stepwise increase in the values of dielectric parameters (εʹ and εʺ). The calculated value of frequency exponent “s” and its variation with temperature suggested the use of correlated barrier hopping model for understanding the AC conduction mechanism of prepared alloys.