Structural evolution of ultrathin film iron oxide and BiFeO$_{3}$ in ozone assisted MBE deposition

Iron oxide films were grown on sapphire (0001) surfaces using nominally 100{\%} ozone. Both of monolayer-wise deposition and continuous deposition were tried to find the structures of the films at the start of the film formation. The studies utilized x-ray scattering with synchrotron radiation from the Advanced Photon Source. Consideration of substrate and film structures predicts Fe$_{2}$O$_{3}$(0001) (hematite) film formation. However, in both of the deposition modes, the initial films formed as magnetite Fe$_{3}$O$_{4}$(111). As the film growth progresses, hematite (Fe$_{2}$O$_{3}$(0001)) appears. At the later stage, the magnetite disappears and the whole film turned to hematite. The same techniques were employed for the investigation of BiFeO$_{3}$ growth. At the early stages, the layer spacing showed interesting variation through the film. The influence of the interfaces will be discussed