Ab Initio Study of Novel Phase-Change Heterostructures

Neuromorphic devices constitute a novel approach to computing that takes inspiration from the brain to unify the processing and storage units. Memories based on phase-change materials (PCMs) are potential candidates for such devices due to their non-volatility and excellent scalability, however their use is hindered by their conductance variability and temporal drift in resistance. Recently, it has been shown that the utilization of phase-change heterostructures consisting of nanolayers of the Sb₂Te₃ PCM interleaved with a transition-metal dichalcogenide, acting as a confinement material, strongly mitigates these problems. In this work, superlattice heterostructures made of TiTe₂ and two prototypical PCMs, respectively GeTe and Ge₂Sb₂Te₅ are considered. By performing ab initio molecular dynamics simulations, it is shown that it is possible to switch the PCMs without destroying the superlattice structure and without diffusion of the atoms of the PCM across the TiTe₂ nanolayers. In particular, the model containing Ge₂Sb₂Te₅ shows weak coupling between the two materials during the switching process, which, combined with the high stability of the amorphous state of Ge₂Sb₂Te₅, makes it a very promising candidate for neuromorphic computing applications.