https://www.techpowerup.com/245530/n...pete-with-dram

Researchers at IBM Zurich and Germany University of RTWH Aachen have developed a new non-volatile phase change memory with monoatomic glassy antimony, which unlike conventional phase-change-materials uses just a single element: antimony (Sb). Traditional phase-change memories use a mix of different materials, which makes things complicated when you try to shrink them down for higher storage densities, as impurities and composition differences negatively affect yields.

The novel approach is based on pure antimony films that are between 3 and 10 nanometers thick, confined between Silicon layers of 40-200 nm thickness. For their prototypes the engineers achieved a switching rate of 50 nanoseconds (20 MHz). While this doesn't sound very fast, the researchers are optimistic that this can be optimized further, their next goal is 10 nanoseconds, which is getting in the region of DRAM speeds.