Synchrotron X-ray scattering of (Ba0.5Sr0.5)TiO3 thin films epitaxially grown on MgO(100)

(Ba0.5Sr0.5)TiO3 thin films of two different thicknesses (similar to 250 Angstrom and similar to 1330 Angstrom) epitaxially prepared on MgO(100) using pulsed laser deposition were studied by synchrotron x-ray scattering measurements. The film initially grew on MgO(100) with a cube-on-cube relationship, maintaining it during further growth. As the film grew, the surface of the film became rougher significantly, but the interface between the film and the substrate did not change so much. In the early stage, the film was highly strained in a tetragonal structure with the longer axis parallel to the surface normal direction. As the growth proceeded further, it was mostly relaxed to a cubic structure with the lattice parameter of the bulk value and the mosaic distribution improved significantly in both the in-plane and the out-of-plane directions. The thinner film showed only one domain limited mainly by the film thickness, but the thicker film exhibited three domains along the surface normal direction.