Photoemission study on protonic conductor p-type SrTiO3

The electronic structure of Sc-doped p-type SrTiO 3 has been studied by photoemission spectroscopy. Comparing the results with those of Nb-doped n-type SrTiO 3 , the Fermi level of p-type is shifted to the low binding energy. As Sc dopant increases, the top of the valence band is shifted to the low binding energy in accord with the rigid-band model. The Ti 3d component in the O 2p band of p-type SrTiO 3 increases compared with that of the n-type one. It was also found that the satellite intensities of Ti core levels drastically increase. The covalency of p-type SrTiO 3 increases by the doping of the Sc ions. The dopant concentration dependence shows that the covalency is strongest when the Sc concentration is 2 mol%. These facts suggest that the covalency is related to the protonic conduction.