New insights on the crystallization process in Ge15Sb85 phase change material: A simultaneous calorimetric and quick-EXAFS measurement

A simultaneous X-ray absorption spectroscopy and calorimetric experiment was performed on the binary Ge15Sb85 phase change material in order to obtain a deeper understanding of the two-step crystallization mechanism. The combination of these techniques allows monitoring the structural and thermal changes related to the crystallization process with a time resolution of the order of 1 s. Both observed crystallization transitions go along with significant atomic rearrangements affecting not only the radial distribution function, but also the amplitude of thermal vibrations. From these data, the stoichiometry of the crystallized phases is also extracted.

► The two-step crystallization process in amorphous Ge15Sb85 is studied.
► The structural mechanisms leading to the phase separation are proposed.
► A rich-Sb phase crystallizes at 514 K and the Ge atoms start to segregate.
► At 604 K, the as-formed amorphous Ge regions crystallize.