Ab initio study on the fast reversible phase transitions of Ge2Sb2Te5

Abstract

Ge2Sb2Te5 (GST) alloy has the ability to quickly transform between the amorphous phase and the crystalline phase; therefore, it can be used in non-volatile phase change storage. First-principles molecular dynamics was used to simulate the reversible phase change process of GST alloy, namely, amorphization and crystallization. The amorphous state was obtained by melting (∼3000 K) and cooling, and the amorphization process was characterized by the pair correlation function and bond angle distribution. The bond angles of amorphous GST were mainly distributed around 60°, 90°, and 110°, indicating the existence of octahedral and tetrahedral bonding configurations. The crystalline state was obtained by annealing at a temperature of 600 K, and the crystallization process was characterized by the pair correlation function, component disordered number, bond angle distribution, and dynamic atomic structure change. The results show that the bond angle of GST in crystallization is mainly distributed around 90°, and the structure mainly contains four-membered rings formed by Ge–Te and Sb–Te. By analyzing the optical properties, with the growth of crystallization time, the absorption coefficient, reflectivity, and conductivity of GST were significantly improved.