Investigation of electronic states of infinite-layer SrFeO2 epitaxial thin films by X-ray photoemission and absorption spectroscopies

We investigated the electronic states of a single-crystal SrFeO2 epitaxial thin film in the valence-band and conduction-band regions using synchrotron-radiation X-ray photoemission and absorption spectroscopies. Fe 2p-3d resonant photoemission measurements revealed that the Fe 3d states have higher densities of states at binding energies of 3-5 eV and 5-8.5 eV in the valence-band region. The O K-edge X-ray absorption spectrum exhibited three peaks in the Fe 3d-derived conduction band hybridized with O 2p states; these can be assigned to Fe 3d(xy), 3d(x2) + 3d(yx), and 3d(x2-y2). In addition, the indirect bandgap value of the SrFeO2 film was determined to be 1.3 eV by transmission and absorption spectroscopies. (C) 2011 Elsevier B.V. All rights reserved.