Multi-scale Analysis of the Crystallization of Amorphous Germanium Telluride

Abstract

The crystallization properties of the phase change material (PCM) germanium telluride (GeTe) are investigated. It is shown that the critical nucleus radius of a crystalline cluster is smaller than 1.4nm when the annealing temperature is lower than 600K, indicating an extremely promising scaling scenario. It is revealed 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. The methodology proposed here is capable of quantitatively calculating the nucleation rate and growth speed of amorphous PCM from first principle calculations, which is relevant to computational design and optimization of PCM.

Phase-change materials for non-volatile memory devices: from technological challenges to materials science issues

“…Second, the conduction mechanism in the smallest structures will be significantly affected by geometrical confinement. Indeed, a dramatic change in the conduction behavior in the smallest structures with ultimate down-sizing is predicted by existing models for electrical conduction in PCMs [221][222][223][224]. As a result, the scalability limit of threshold switching combined with reliability of the resistance contrast have to be properly defined for ultimately scaled memory structures.…”