Critical thickness of high structural quality SrTiO3 films grown on orthorhombic (101) DyScO3

Abstract

Strained epitaxial SrTiO3 films were grown on orthorhombic (101) DyScO3 substrates by reactive molecular-beam epitaxy. The epitaxy of this substrate/film combination is cube on cube with a pseudocubic out-of-plane (001) orientation. The strain state and structural perfection of films with thicknesses ranging from 50 to 1000 Å were examined using x-ray scattering. The critical thickness at which misfit dislocations was introduced was between 350 and 500 Å. These films have the narrowest rocking curves (full width at half maximum) ever reported for any heteroepitaxial oxide film (0.0018°). Only a modest amount of relaxation is seen in films exceeding the critical thicknesses even after postdeposition annealing at 700 °C in 1 atm of oxygen. The dependence of strain relaxation on crystallographic direction is attributed to the anisotropy of the substrate. These SrTiO3 films show structural quality more typical of semiconductors such as GaAs and silicon than perovskite materials; their structural relaxation behavior also shows similarity to that of compound semiconductor films.