Impact of atomic vacancy on phase change and structure in Ge x Te 1−x films

Binary compound Ge–Te, which displays intriguing functionalities, has been intensively studied from both fundamental and technological perspectives. In Ge–Te compound, a deviation from the Ge–Te stoichiometry will lead it thermodynamically unstable as well as to the change in the phase change characters. In this study, a series of non-stoichiometric Ge–Te films were prepared and a detailed study on the impact of Ge vacancy was carried out. The phase change characters can be tuned by adjusting the composition. Although the Ge vacancy does not lead to phase separation and Te precipitation in these films, Raman spectroscopy analysis reveals a dramatic change in the bonding environment. The microstructure has been modified by the induced Ge vacancy, especially the threefold Te unit and Ge–Ge bond in the crystalline GeTe.