Direct observation of metastable face-centered cubic Sb₂Te₃ crystal

Although phase change memory technology has developed drastically in the past two decades, the cognition of the key switching materials still ignores an important member, the face-centered cubic Sb₂Te₃. Apart from the well-known equilibrium hexagonal Sb₂Te₃ crystal, we prove the metastable face-centered cubic Sb₂Te₃ phase does exist. Such a metastable crystal contains a large concentration of vacancies randomly occupying the cationic lattice sites. The face-centered cubic to hexagonal phase transformation of Sb₂Te₃, accompanied by vacancy aggregation, occurs at a quite lower temperature compared to that of Ge₂Sb₂Te₅ alloy. We prove that the covalent-like bonds prevail in the metastable Sb₂Te₃ crystal, deviating from the ideal resonant features. If a proper doping technique is adopted, the metastable Sb₂Te₃ phase could be promising for realizing reversibly swift and low-energy phase change memory applications. Our study may offer a new insight into commercialized Ge–Sb–Te systems and help in the design of novel phase change materials to boost the performances of the phase change memory device.