SURFACE-STRUCTURE AND ELECTRONIC PROPERTY OF REDUCED SRTIO3(100) SURFACE OBSERVED BY SCANNING TUNNELING MICROSCOPY SPECTROSCOPY

We have obtained the scanning tunneling microscopy (STM) images and scanning tunneling spectroscopy (STS) data with atomic-scale resolution for a SrTiO3(100) surface annealed in ultrahigh vacuum (UHV) at 1200-degrees-C. A square-root 5 x square-root 5 - R26.6-degrees surface superstructure indicating oxygen vacancy ordering has been observed. The STS data provide evidence for a localized surface state arising from oxygen vacancies at 1.35 eV below the Fermi level. STM images of the square-root 5 X square-root 5 structure correspond to the surface orbital of the ordered Ti-oxygen vacancy complex.