Electronic structure of proton conducting SrCeO3–SrZrO3 thin films

The electronic structure of the protonic conductor Sr[Ce1−xZrx]0.95Yb0.05O3−δ thin film has been studied by soft-X-ray spectroscopy. The valence band is composed mainly of the O 2p state. The conduction band is composed of Ce 4f and Zr 4d states. The holes and acceptor level are observed at the top of the valence band and just above the Fermi level (EF), respectively. In H2-annealed Sr[Ce1−xZrx]0.95Yb0.05O3−δ thin films, their intensities decrease and the hydrogen-induced level is created at just below EF. The energy separation between the bottom of the hydrogen-induced level and the top of the valence band agrees with the activation energy estimated from the electrical conductivity.