Lattice-work structure of a TiO2(0 0 1) surface studied by STM, core-level spectroscopies and DFT calculations

The lattice-work structure of a rutile TiO2(0 0 1) surface, which is faceted to {1 1 4} plane, was studied by combining scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS) and density functional theory (DFT) calculations. Synchrotron XPS and NEXAFS spectra taken for the faceted surface indicated that this surface possesses a stoichiometric composition. We propose a new stoichiometric structure model on the basis of XPS, NEXAFS, and atomically-resolved STM observations. DFT calculations revealed that the present stoichiometric model is energetically more favorable compared to the previously proposed models.