A multi-scale analysis of the crystallization of amorphous germanium telluride using ab initio simulations and classical crystallization theory

The crystallization properties of the prototypical binary phase change material (PCM) germanium telluride (GeTe) are investigated by combining crystallization theory with ab initio molecular dynamics simulations. The temperature dependence of the physical quantities that determine the crystallization properties is calculated and analyzed. It is shown that the critical nucleus radius of a crystalline cluster is smaller than 1.4 nm when the annealing temperature is lower than 600 K, indicating an extremely promising scaling scenario. Our analysis reveals that the elastic energy, which is largely ignored in existing PCM crystallization studies, plays an important role in determining various crystallization properties and the ultimate scaling limit of the PCM. By omitting the influence of elastic energy, the critical formation energy (critical nuclei radius) will be underestimated by 41.7% (22.4%), and the nucleation rate will be overestimated by 74.2% when the annealing temperature is 600 K. (C) 2014 AIP Publishing LLC.