Growing of YBaCo4O7 + δ thin films on α-Al2O3 and SrTiO3 substrates by means of the pulsed laser deposition technique

Thin films of the layered cobaltate YBaCo4O7 + δ were deposited by means of the pulsed laser deposition technique on c-axis oriented sapphire (α-Al2O3) and (001)-oriented SrTiO3 substrates. X-ray diffraction patterns of the YBaCo4O7 + δ layers on sapphire substrates evidence a (001) and (101) oriented textured growth with a preferential out-of-plane orientation of the c-axis of the film. Since the lattice mismatch between film and substrate is fairly large, the observed texture is likely a consequence of the crystallographic anisotropy (c/a) of YBaCo4O7 + δ. Films grown on SrTiO3 substrates show a reduced crystalline quality compared to those films grown on α-Al2O3 and are usually affected by impurity phases. This might be caused by the poor lattice matching between cubic SrTiO3 and hexagonal YBaCo4O7 + δ. The mosaic spread of the films, determined by the full width at half maximum of rocking curves, amounts to 2° and 3° for films grown on α-Al2O3 and (001)-SrTiO3, respectively. The atomic composition of the films with respect to the cations was evaluated via Rutherford backscattering spectroscopy and found to be close to the nominal one. The results show that textured YBaCo4O7 + δ films can be easily obtained on commercially available substrates.