Electronic structures near surfaces of perovskite type oxides

This work is intended to draw attention to the origin of the electronic structures near surfaces of perovskite type oxides. Deep states were observed by ultraviolet photoelectron spectroscopic measurements. The film thickness dependent electronic structures near surfaces of (Ba0.5Sr0.5)TiO3 thin films were observed. As for the 117-308 nm thick (Ba0.5Sr0.5)TiO3 films, deep states were lying at 0.20, 0.55, and 0.85 eV below the quasi-fermi level, respectively. However, as for the 40 nm thick (Ba0.5Sr0.5)TiO3 film, the states were overlapped. The A-site doping affected electronic structures near surfaces of SrTiO3 single crystals. No evolution of deep states in non-doped SrTiO3 single crystal was observed. However, the evolution of deep states in La-doped SrTiO3 single crystal was observed.