  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.
