Tutorial EQ10: Advanced Memory and Computing Technologies Using Phase Change Materials

Fabrizio Acriprete, University of Rome Tor Vergata

Molecular Beam Epitaxial Growth and Characterization of Phase Change Memory Materials

Written by Mohamed Atwa     

Fabrizio Acriprete gave a deep-dive talk into the epitaxial growth and materials characterization of the most famous phase change memory material: germanium antimony telluride (GST). He started off by briefly touching on the applications of phase change memory (PCM) to embedded systems storage applications as well as to more exotic applications such as neuromorphic memory and nonvolatile photonics. He then described the various techniques employed in both industry and academia to grow epitaxial films of PCM materials. Specifically, he highlighted the pros and cons of MBE, PLD, and sputtering and showed the most common use cases for each. He moved on to the various crystal structures adopted by GST and its individual constituents: GeTe and Sb₂Te_3­. He touched briefly on the fundamental interest in the metal-insulator transition exhibited by GSTs when they change structure between their amorphous and crystalline phases. While amorphous GSTs are more insulating, crystalline GSTs are more conducting. This, he explained, was due to the change in vacancy ordering between the two phases. He segued into the compositional and structural tuning GSTs by varying the elemental fluxes, substrate types, and deposition temperatures of GSTs during MBE growth. Acriprete ended the talk by discussing a variety of experimental techniques used to probe the electronic structure of GSTs including time-resolved photoemission, angle-resolved photo-spectroscopy, and X-ray photo-spectroscopy. Overall, the session was an excellent exploration of the materials science-side of phase change memory materials.