The properties of complex oxide films depend sensitively on epitaxial strain. This strain affects bond lengths and angles, and defect types and densities, thus impacting physical properties. In this work we perform detailed characterization of depth-dependent strain in epitaxial La0.5Sr 0.5CoO3-δ (LSCO) films on SrTiO3(001), SrTiO3(110), and LaAlO3(001) substrates, combining high resolution x-ray diffraction and scanning transmission electron microscopy, in addition to geometric phase analysis. We elucidate a fundamental link between strain state and O vacancy ordering in LSCO films, where lattice mismatch and crystallographic orientation can be used to manipulate the modulation vector of the long-range vacancy order, thus providing a new approach to tailor the properties of such films.
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We thank Julia Luck for STEM specimen preparation, and Roger Guzman for assistance with GPA. Research at ORNL (electron microscopy) was supported by the US Department of Energy (DOE), Basic Energy Sciences (BES), Materials Sciences and Engineering Division (SJP and MV), and a user project was supported by ORNL's Shared Research Equipment (ShaRE) User Program, also sponsored by DOE-BES. J.G. acknowledges support from the Spanish MEC 2007-0086 and the European Research Council Starting Investigator Award STEMOX 239739. Work at UMN was supported by NSF (DMR-0804432) and DOE (DE-FG02-06ER46275, specifically scattering characterization).