Microstructural and optical properties tuning of BiFeO3 thin films elaborated by magnetron sputtering

Multiferroic BiFeO 3 thin films were deposited using a conventional RF magnetron sputtering technique on Si substrate. The influence of the microstructure of BiFeO 3 thin films on their optical properties was investigated through an extensive characterization. Using X-ray diffraction and atomic force microscopy, the structure and crystalline quality of the films were studied with regard to the effect of oxygen partial pressure during the deposition and to post annealing treatment. Stoichiometric films with the crystallographic perovskite structure required for multiferroic behaviour were obtained. It is demonstrated that films annealed at 700 °C in oxygen at atmospheric pressure are highly (100) perovskite orientated and free of the undesired phases. This perovskite phase is observed only for a narrow range of oxygen partial pressure The refractive index and extinction coefficient were obtained using variable angle spectroscopic ellipsometry. The optical characteristics of the films are directly correlated to their microstructural properties. Ellipsometry analysis showed that we can tune the optical constants of BiFeO 3 films by controlling the oxygen partial pressure during deposition.