Structural properties of slightly off-stoichiometric homoepitaxial SrTixO3-δ thin films

Ti-deficient SrTixO3-delta films, x < 1, were grown on < 100 > oriented SrTiO3 single crystal substrates by radio frequency magnetron sputtering from stoichiometric targets. The Ti-deficiency was adjusted by the sputtering gas pressure. The Ti/Sr cation ratio, x, was determined by Rutherford backscattering and energy dispersive x-ray analysis in a scanning electron microscope. To obtain information on the Ti/O ratio, x-ray absorption spectroscopy was carried out as well. We investigated SrTixO3-delta films with x=0.98, 0.95, and 0.89. The epitaxial growth and lattice imperfections were characterized by x-ray diffraction, electron diffraction, and high resolution transmission electron microscopy. The films crystallized in a tetragonal structure with a maximum mosaic spread of about 0.1 degrees. The c axis was oriented perpendicular to the substrate surface where the c-lattice parameter was increasing with decreasing x. For x > 0.89, the Ti deficiency was primarily compensated by a change of the site occupation on the cation sublattices in combination with oxygen vacancies, i.e., the formation of Sr-Ti and V-O point defects, whereas for x < 0.95 the intergrowth of homologs series of the Ruddlesden-Popper phases, Srn+1TinO3n+1, was observed. The dielectric properties of the films are briefly discussed in terms of (SrTiVO) defect complexes. (C) 2000 American Institute of Physics. [S0021-8979(00)02016-8].