Structure and electronic state of the TiO2 and SrO terminated SrTiO3(100) surfaces

Structure and electronic state of two kinds of SrTiO3(100) surfaces, selectively formed TiO2 terminated and SrO terminated surfaces, are studied by means of reflection high energy electron diffraction (RHEED), XPS and UPS. It is revealed that for both terminated surfaces, the distances between the 1st and 2nd layer are expanded, where that for the TiO2 and SrO surfaces are 1.95 + 0.07 Å and 1.95 + 0.10 Å, respectively. Furthermore, the oxygen atoms on the outermost surface are pulled out for 0.10 Å and 0.16 Å, respectively. The electronic state near the Fermi level mainly consists of the Ti3d and O2p orbitals and is found to be sensitive to the coordination around the Ti atom; i.e., for the SrO terminated surface, where Ti is coordinated octahedrally by oxygen, a narrow band is observed, while for the TiO2 terminated surface changes in the symmetry from Oh to C4v result in the broadening of the band structure.