Evidence for Ge2Sb2Te5 phase formation upon crystallization of Ge-doped Sb2Te3 phase change films

Abstract

In this work, we investigated the phase transition characteristics of Ge-doped Sb2Te3 phase change films prepared by the magnetron sputtering method. During the crystallization process of Ge-doped Sb2Te3 films, we observed a metastable phase and identified its crystal structure as the face-centered cubic Ge2Sb2Te5, a previously uncharacterized phenomenon. The Te phase precipitated upon crystallization of Sb2Te3 films, while the Te phase disappeared and the Ge2Sb2Te5 phase appeared upon crystallization of Ge-doped Sb2Te3 films, resulting in the coexistence of Ge2Sb2Te5 and Sb2Te3 phases in the single-layer Ge-doped Sb2Te3 films. The appearance of the Ge2Sb2Te5 phase resulted from the formation of Ge–Te bonds due to the combination of the precipitated Te phase with the incorporated Ge. Furthermore, the formation of the Ge2Sb2Te5 phase was mainly responsible for the increased crystalline resistance and crystallization temperature of Sb2Te3 films. The surface roughness of Ge-doped Sb2Te3 films was significantly reduced, exhibiting good potential for improving the contact performance between the films and electrodes. Our findings contribute to enhancing the understanding of Ge-doped Sb2Te3 films and their role in phase change memory technology.