Obtaining glasses in the extremely crystallizing Ge–Sb–Te phase change material

Abstract Using thermal co-evaporation techniques, we show that various glassy compositions can be obtained along the GexSbxTe100-2x join in the ternary Ge–Sb–Te system which is known to display dramatic crystallization tendencies. Earlier attempts to produce bulk glasses have been limited to Sb-poor compositions close to the eutectic GeTe6. Results indicate a weak variation of Tg with composition x and also a thermal stability that is weak for most systems, and especially for compositions close to the domain where Ge2Sb2Te5 can be formed. Our results are put in perspective with other network-forming chalcogenides and the Tg variation suggests the preferential formation of Te–Sb–Te, at variance with isochemical compounds such as Ge–Sb–Se. Data are discussed within the framework of topological based approaches which not only indicate that optimal glass formation is achieved for compositions satisfying the Maxwell stability criterion but also predict a flexible to rigid transition at x = 8.5 %. Most of our glasses could be formed around this composition.