Phase-change alloys are a class of important materials for data-storage applications. Despite the strong technological interest, many fundamental properties of these materials remain poorly understood.
Phase-change alloys are a class of important materials for data-storage applications. Ge2Sb2Te5, as the prototype of these phase-change materials, is already used in rewriteable optical data storage and offers great potential as an emerging non-volatile electronic memory. This application takes advantage of the significant optical/electronic property contrast between the amorphous (a-GST) and the crystalline (c-GST) states, as well as the rapid switch between these two GST polymorphs at elevated temperatures (the a-GST crystallizes on the time scale of several nanoseconds).
Despite the strong technological interest, many fundamental properties of these materials remain poorly understood. A crucial issue is to understand the atomic structure of a-GST and c-GST, such that one can understand the mechanism of the fast phase transition and large property contrast. In our research, the local structure of a-GST is studied with ab-initio molecular dynamics simulations and X-ray diffraction. A signature local structure with right-angled motifs is discovered in this glass, which is characterized by dative bonds formed between Ge and Te. The fast phase transition is believed to be closely related to this structural feature.