Characterisation of epitaxial TiO2 thin films grown on MgO(0Â 0Â 1) using atomic layer deposition

Thin films of TiO2 have been deposited onto MgO(0 0 1) substrates using atomic layer deposition at 300 °C. Plan and cross-sectional transmission electron microscopy (TEM), X-ray diffraction and atomic force microscopy have been used to understand the nature of the films. X-ray and electron diffraction showed that a polycrystalline, epitaxial anatase film was produced. The c-axis of the anatase was parallel to the MgO(0 0 1) surface with two orientational variants at right angles to each other in the plane of the film, each aligned with an MgO cube axis. Plan-view and cross-sectional TEM showed that the grain structure of the film reflected this orientation relationship, with the grain morphology comprising two sets of roughly tetragonal grains. Also present was a small fraction of equiaxed, anatase grains which were randomly oriented. Roughness measurement using atomic force microscopy showed that the epitaxial anatase films were quite smooth, in comparison to equivalent non-aligned films grown on silicon.