Femtosecond x-ray diffraction reveals a liquid–liquid phase transition in phase-change materials

TLDR

Phase‑change materials enable rapid, thermally driven switching between glassy and crystalline states, allowing fast memory write and long‑term retention. The study used ultrafast X‑ray diffraction and simulations to probe the atomic structure of two phase‑change materials during switching. Both materials exhibit a liquid‑liquid phase transition that facilitates rapid high‑temperature switching, while the resulting low‑temperature glass state preserves the structure for durable memory. Zalde et al., Science, this issue p.

Abstract

Structural switch for fast switching Phase-change materials are important for computer memory. They can quickly switch from glassy to crystalline using a thermal pulse and then lock in that structure for a long time at lower temperature. Zalde et al. probed the underlying atomic structure of two phase-change materials during this switching using ultrafast x-rays and simulations (see the Perspective by Rao et al. ). A liquid-liquid phase transition in both materials allowed fast switching at high temperatures. The lower-temperature glass locks in the structure, allowing for long-term memory storage. Science , this issue p. 1062 ; see also p. 1032