Time-temperature-transformation and continuous-heating-transformation diagrams of GeSb2Te4 from nanosecond-long ab initio molecular dynamics simulations

Abstract We use ab initio molecular dynamics (AIMD) simulations to build an amorphous model of GeSb 2 Te 4 and nanosecond-long annealing AIMD simulations to construct its Time-Temperature-Transformation (TTT) and Continuous-Heating-Transformation (CHT) diagrams. The critical cooling rate for amorphous GeSb 2 Te 4 , derived from the “nose” of the TTT diagram, is in the range 470–1100 K/ns. The Kissinger analysis of the non-isothermal crystallization kinetics suggests that it follows a non-Arrhenius crystallization behavior in which the crystallization temperature is upshifted by the heating rates. These results, from unprecedentedly long AIMD simulations, provide a detailed picture of the complex crystallization of GST alloys at the extremely small time and length scales relevant to phase change memory devices.