Anisotropic-strain-relaxation-induced crosshatch morphology in epitaxial SrTiO3/NdGaO3 thin films

Abstract

We investigate the strain relaxation and surface morphology of epitaxial SrTiO3 (STO) films grown on (001)O and (110)O planes of orthorhombic NdGaO3 (NGO), and (001) plane of cubic (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) substrates. Although the average lattice mismatches are similar, strikingly regular crosshatched surface patterns can be found on STO/NGO(001)O[(110)O] films, contrary to the uniform surface of STO/LSAT(001). Based on the orientation and thickness dependent patterns and high-resolution x-ray diffractions, we ascribe the crosshatch morphology to the anisotropic strain relaxation with possibly the 60° misfit dislocation formation and lateral surface step flow in STO/NGO films, while an isotropic strain relaxation in STO/LSAT. Further, we show that the crosshatched STO/NGO(110)O surface could be utilized as a template to modify the magnetotransport properties of epitaxial La0.6Ca0.4MnO3 films. This study highlights the crucial role of symmetry mismatch in determining the surface morphology of the perovskite oxide films, in addition to their epitaxial strain states, and offers a different route for designing and fabricating functional perovskite-oxide devices. © 2014 Author(s).