Functional Properties of Phase Change Materials from Atomistic Simulations

Abstract

Chalcogenide alloys are materials of interest for optical recording and electronic nonvolatile memories. These applications rest on an ensemble of functional properties: a fast and reversible transformation between the amorphous and the crystalline phase upon heating and a strong optical and electronic contrast between the two phases that allow discriminating the two states of the memory. We discuss the insights gained from atomistic simulations based on Density Functional Theory on the functional properties of the prototypical phase change compounds Ge 2 Sb 2 Te 5 and GeTe. We review the results on the structural and bonding properties of the crystalline and amorphous phases, the origin of the optical and electronic contrast between the two phases and the source of the fast crystallization of the supercooled liquid. The results on the crystallization kinetics obtained from large scale simulations with interatomic potentials based on Neural Network methods are also discussed.