Orientation control of textured SrTiO3 thin films on platinized α-Al2O3 (0001) by an ion beam sputter deposition method

SrTiO3 (STO) thin films were grown on Pt/Al2O3 substrates without a Ti adhesion layer by an ion beam sputter deposition method in a range of growth temperatures between 600 and 750 degrees C. The effect of growth temperature on the film orientation was investigated by high-resolution x-ray diffraction, pole figure measurements and in-plane grazing incidence x-ray diffraction. The film orientation showed a strong dependence on the growth temperature. The films exhibited a predominant (1 1 0) orientation at a low growth temperature of 600 degrees C. With an increase in growth temperature to 750 degrees C, a highly (1 1 1)-textured STO film with two different orientation variants was achieved on the Pt/Al2O3 substrate. A narrow full-width at half-maximum of 0.12. for the rocking curve measured on 2 2 2(STO) reflection and a six-fold symmetry from {1 0 0}(STO) and {1 1 0}(STO) pole figures were observed. Three-dimensional island growth mode was observed on the surfaces of all films, as investigated with an atomic force microscope. The evolution of grain shape and size was apparently found with an increase in growth temperature. The root-mean-square roughness of the STO film grown at 750 degrees C was raised to be about 4 nm due to the surface faceting of (1 1 1)-oriented grains. The growth mechanism of the (1 1 0)- and (1 1 1)-textured STO films on the Pt/Al2O3 substrates was also explained and discussed in detail.