A multi-scale analysis of the impact of pressure on melting of crystalline phase change material germanium telluride

Abstract

The impact of the moderate pressure (about 100 GPa) on the melting of crystalline (c-) phase change material (PCM) germanium telluride (GeTe) is analyzed, by combining the heat transfer equation in the PCM device scale (101–102 nm and beyond), and the ab initio molecular dynamics and the nudged elastic band simulations in the atomistic scale (10−1–100 nm). The multi-scale analysis unravels that a pressure P = 1.0 GPa can increase the melting temperature of c-GeTe and the PCM device “reset” operation energy consumption by 6%–7%. It is shown that the melting temperature increase originates from the pressure-induced raise of the energy barrier of the umbrella-flip transition of the Ge atom from the octahedral symmetry site to the tetrahedral symmetry site. It is revealed that when P > 1.0 GPa, which is normal in PCM devices, the “reset” energy will be increased even by more. Based on the analysis, suggestions to alleviate pressure-induced raise of melting temperature and “reset” energy are provided.