Ultrathin TiO2 Films on (1x2)-Pt(110): a LEED, Photoemission, STM, and Theoretical Investigation

The preparation and characterization of fully oxidized TiO2 ultrathin films obtained by reactive deposition of Ti in an O-2 background on the (1x2)-Pt(110) reconstructed surface is described in details. The structure, the electronic properties, and the morphology of the epitaxial films giving rise to a (14x4) coincidence superstructure are discussed on the basis of low-energy electron diffraction, photoemission (both core and valence band), angle-scanned X-ray photoelectron diffraction, scanning tunneling microscopy data, and density functional theory calculations. We show that the oxide overlayer is a stoichiometric lepidocrocite-like single-domain nanosheet. This can be thought of as originating from a (100) oriented anatase bilayer which spontaneously restructure by a uniaxial relative sliding of one single layer with respect to the other by half a unit cell. According to the results of theoretical calculations, the process is self-driven by the spatial confinement, whereas a minor role is played by the interaction with the substrate. The occurrence of the (14x4) coincidence between the overlayer and the substrate is fully rationalized on the basis of the reported data.