Stabilization of the Perovskite Phase in the Y–Bi–O System By Using a BaBiO₃ Buffer Layer

A topological insulating phase has theoretically been predicted for the thermodynamically unstable perovskite phase of YBiO₃. Here, it is shown that the crystal structure of the Y–Bi–O system can be controlled by using a BaBiO₃ buffer layer. The BaBiO₃ film overcomes the large lattice mismatch of 12% with the SrTiO₃ substrate by forming a rocksalt structure in between the two perovskite structures. Depositing an YBiO₃ film directly on a SrTiO₃ substrate gives a fluorite structure. However, when the Y–Bi–O system is deposited on top of the buffer layer with the correct crystal phase and comparable lattice constant, a single oriented perovskite structure with the expected lattice constants is observed.