Thermodynamic description of the Ge-Sb-Te phase change materials and its applications in predictions of crystallization and solidification

Abstract

Phase change memory (PCM) is characterized in its high speed, high stability and low power consumption. The investigation of stoichiometric variation, precipitation kinetics, microstructure simulation, non-isothermal and non-equilibrium conditions are significant in the development of PCM, in which the thermodynamic database is absolutely necessary. However, there is no available database of the Ge-Sb-Te ternary system and there exists some contradictions in the reported phase relations. This study elucidates these contradictions by measuring the phase relations of the Ge-Sb-Te ternary system at 673 K. Combined with the measured results and the first-principles method, the thermodynamic description in the whole composition range of the Ge-Sb-Te ternary system is evaluated by the CALculation of PHAse Diagram (CALPHAD) approach with the reassessment of the Ge-Te and Sb-Te binary systems. To provide possibilities for future volume effect research, the molar volume of the liquid phases and Ge₂Sb₂Te₅, are also performed based on literature data. Finally, the thermodynamic description carried in this work is used to predict the amorphous forming ability. A local minimum value of the max driving force is found, which predicted owns good amorphous forming ability. In addition, the phase composition of crystallization and solidification products are also can be predicted using the thermodynamic description. The present work could contribute to the research of the Ge-Sb-Te phase change memory and future assessment of multicomponent systems.