Interfacial stability of ultrathin film magnetite (Fe$_{3}$O$_{4})$ 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. Real time and static x-ray diffraction results show the same result. Possibility of the oxidation limited transformation should be excluded. Other possible cause of this reverse stability will be discussed.