EFFECT OF SURFACE OXYGEN VACANCIES ON ELECTRONIC STATES OF REDUCED SRTIO3(110) SURFACE

The electronic structure of reduced SrTiO3(110) surface prepared by annealing in ultrahigh vacuum UHV), has been studied using photoemission spectroscopy (PES) and scanning tunneling microscopy/spectroscopy (STM/STS). In the PES spectra of reduced SrTiO3(110) surface after annealing in UHV at 800 degrees C, a clear metallic state with a sharp Fermi cut-off and a broad state centered at similar to 1.1eV below the Fermi level are observed in the band gap region. A Ti3p->3d resonance enhancement is occurred for the metallic state, but not for the similar to 1.1eV state. On the other hand, after the sample was annealed in UHV at 1000 degrees C, it has been shown that the metallic state becomes drastically weak, and that only the similar to 1.1eV state is seen in the band gap region. Thereafter, the similar to 1.1eV state exhibits a clear Ti3p->3d resonance enhancement. The difference in the spectral feature of these band gap states is directly related to the surface geometric structural change.