Electrical and structural properties of BaCe0.85Ru0.05Y0.10O3−δ thin film prepared by RF magnetron sputtering

The a- and c-axes-oriented BaCe0.85Ru0.05Y0.10O3−δ (BCRY) thin films have been deposited on Nb-SrTiO3(100) substrates by radio frequency (RF) magnetron sputtering. Such BCRY thin films have mixed valence states of Ce4+ and Ce3+. The activation energies (E A) for the conductivity of films thicker than 200 nm are 0.23–0.26 eV, which corresponds to half E A of bulk ceramics, below 400 °C. The BCRY thin films exhibit ion conduction at the bulk region and electron–ion mixed conduction at the surface region. Proton conduction is also observed in the surface state in addition to the mixed conduction. The Fermi levels (E F) locate at the middle position in the band gap region, although E F of the BaCe0.90Y0.10O3−δ thin films locates on the valence band side. These results indicate that the Ru5+ ions and protons act as donor ions in BCRY thin films.