Microstructure of BaxSr1-xTiO3 thin films grown on sapphire substrates

High degree of ordering was observed in the SrTiO3, Ba0.1Sr0.9TiO3 and BaTiO3 thin films grown by injection metal-organic chemical vapour deposition on sapphire substrates. Orientation of the Al2O3 substrates was (0 0 1) perpendicular to the surface; orientation of the films was (1 1 1). Atomic ordering at the interface between the substrates and the films approached locally heteroepitaxial growth. Two distinct in-plane orientations of the films were observed. The projection of the [1 0 0] direction in the cubic or cubic-like films was rotated either +30 or -30 deg. with respect to the [1 0 0] crystallographic direction of the substrate. Still, a slight disorientation of the films from the dominant directions was observed. The in-plane disorientation of the films increased with increasing barium contents. In SrTiO3, the in-plane disorientation of crystallites was 1.5 deg. , in BaTiO3 3.2 deg. . The residual stress analysis has shown that the films grew without residual stress at the deposition temperature (800 deg. C). Consequently, the interface layer between films and substrates was very strained but able to pass the in-plane orientation of the substrate to the film