Atomic-resolution study of oxygen vacancy ordering in Lao.5Sro.5CoO3-s thin films on SrTiO3 during in situ cooling experiments.

Abstract

The presence of oxygen vacancy, as well as ordering of vacancies plays an important role in determining the electronic, ionic and thermal transport properties of many transition metal oxide materials. Controlling the concentration of oxygen vacancies as well as the structures or domains of ordered oxygen vacancies has been the subject of many experimental and theoretical studies. In epitaxial thin films, the concentration of oxygen vacancies as well as the type of ordering depends on the structure of the support as well as the lattice mismatch between the thin films and the support. The role of temperature induced structural phase transitions on the oxygen vacancy ordering has remained largely unexplored. Here, we use aberration-corrected scanning transmission electron microscopy (STEM) combined with an in-situ cooling experiments to characterize the atomic/electronic structures of oxygen-deficient $La_{0.5}$$Sr_{0.5}$Co$O_{3-{\delta}}$ thin films grown on SrTi$O_{3}$ across the anti-ferrodistortive phase transition of SrTi$O_{3}$ at 105 K. We demonstrate that atomic-resolution imaging and electron energy-loss spectroscopy (EELS) can be used to examine variations in the local density of states as a function of sample temperature and thus of the structure of the support.