We have investigated the effects of a structure phase transition on the electronic structure in reduced BaTiO3 single crystals by using photoemission spectroscopy. We show that three kinds of structural phase transitions, from cubic to tetragonal, orthorhombic, and rhombohedral structures, are manifested in the core-level spectra of Ba, Ti, and O. Along these second-order phase transitions, we also find a smooth evolution of the valence-band spectra of Ti 3d states, which consist of an oxygen-vacancy-induced in-gap state and a quasi-particle state. Especially, we compare constant energy maps at the Fermi level and the valence-band maximum to other reported data for both BaTiO₃ and SrTiO₃.
We have investigated the effects of a structure phase transition on the electronic structure in reduced BaTiO3 single crystals by using photoemission spectroscopy. We show that three kinds of structural phase transitions, from cubic to tetragonal, orthorhombic, and rhombohedral structures, are manifested in the core-level spectra of Ba, Ti, and O. Along these second-order phase transitions, we also find a smooth evolution of the valence-band spectra of Ti 3d states, which consist of an oxygen-vacancy-induced in-gap state and a quasi-particle state. Especially, we compare constant energy maps at the Fermi level and the valence-band maximum to other reported data for both BaTiO₃ and SrTiO₃.
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