Phase-Change Materials (PCMs), mainly represented by (GeTe) -(Sb2Te3) (GST) alloys, are used for high-density data storage in optical media and for solid-state non-volatile memories. Among all, Ge-rich GeSbTe alloys has been exploited to increase the crystallization temperature and therefore to improve data retention in high-temperature applications of non-volatile phase change memories, such as embedded or automotive products.
Additionally, the development of PCMs for novel applications (e.g. multi-level memories, neuromorphic devices, thermoelectrics, …) requires a precise control of the local crystalline arrangement and of the nanoscale inhomogeneities (i.e. phase separations, defects, vacancy ordering, grain boundaries, precipitates) that must be engineered or avoided.
With the aim of a better insight into the local structural and chemical arrangement of PCMs, I will present nanoscale studies performed by means of conventional Transmission Electron Microscopy (TEM), High Angular Annular Dark Field (HAADF) Scanning/TEM (S/TEM) and correlated nano-analysis techniques.