Electronic structures in the bulk and surface states of protonic conductor CaZrO3 by soft-X-ray spectroscopy

The electronic structure in the bulk state of protonic conductor In-doped CaZrO3 (CZI) has been investigated by soft-X-ray emission spectroscopy (SXES). Comparing with the SXES spectrum of dried CZI, the Fermi level (EF) of proton-doped CZI is shifted to the conduction band side by about 1.0 eV. The SXES spectrum of proton-doped CZI has two features, which correspond to the hole state at the top of the valence band and the proton-induced level near EF. These results indicate that the doped proton acts as a positive charge in the bulk state.