Atomic structure and electronic properties of planar defects in SrFeO3−δ thin films

Abstract

Extended planar defects found in epitaxially grown SrFeO 3-δ thin films are expected to exhibit distinct conductivity properties. Here, we use a combination of scanning transmission electron microscopy techniques and electron energy-loss spectroscopy (EELS) to uncover the peculiar structure of these planar defects and to explore their electronic properties. We find that the defects are formed by Fe 2 O 2+α layers consisting of FeO 5 polyhedra alternating with SrO and FeO 2 perovskite-type layers, analogous to the Sr 4 Fe 6 O 12+δ crystal structure. Our experimental and theoretical EELS data, combined with projected density of states calculations, reveal peak width changes and energies shifts, which suggest an increased electron doping of the Fe 3de g band in the Fe 2 O 2+α layers as compared to the SrFeO 3−δ film. Thus we show that the presence of Fe 2 O 2+α planar defects indeed can effectively modify the electron-hole conductivity in SrFeO 3-δ films.