Complete Mapping of Thermodynamic Stability of Ternary Oxide SrTiO₃ (001) Surface at Finite Temperatures

The oxide surface structure plays a vital role in controlling and utilizing the emergent phenomena occurring at the interface of nanoarchitecture. A complete understanding of ternary oxide surfaces remains challenging due to complex surface reconstructions in various chemical and physical environments. Here a thermodynamic framework is developed to treat the stability of ternary oxide surfaces with finite temperature and chemical environments. Strontium titanate, as a representative ternary oxide, is used to establish the complete energy landscape of SrTiO₃ (001) surface. The complete mapping yields a comprehensive understanding of various stable SrTiO₃ surfaces with finite temperature and chemical potential or vapor pressure of the constituents, i.e., Sr (or Ti) metal and oxygen. This treatment also reveals a stable surface unknown yet with SrTi₂O₃ stoichiometry, which unveils the missing link between numerous previous experimental observations and the current understanding of SrTiO₃ surface. Interestingly, the new surface shows an anisotropic surface-localized metallic state originating from the characteristic surface structure. The findings would provide a viable way to understand ternary oxide surfaces and further utilize SrTiO₃ surfaces for oxide nanoarchitectures.