Crystallization kinetics of nanoconfined GeTe slabs in GeTe/TiTe _2 -like superlattices for phase change memories

Superlattices made of alternating blocks of the phase change compound Sb _2 Te _3 and of TiTe _2 confining layers have been recently proposed for applications in neuromorphic devices. The Sb _2 Te _3 /TiTe _2 heterostructure allows for a better control of multiple intermediate resistance states and for a lower drift with time of the electrical resistance of the amorphous phase. However, Sb _2 Te _3 suffers from a low data retention due to a low crystallization temperature T _x . Substituting Sb _2 Te _3 with a phase change compound with a higher T _x , such as GeTe, seems an interesting option in this respect. Nanoconfinement might, however, alters the crystallization kinetics with respect to the bulk. In this work, we investigated the crystallization process of GeTe nanoconfined in geometries mimicking GeTe/TiTe _2 superlattices by means of molecular dynamics simulations with a machine learning potential. The simulations reveal that nanoconfinement induces a mild reduction in the crystal growth velocities which would not hinder the application of GeTe/TiTe _2 heterostructures in neuromorphic devices with superior data retention.