title: Structure of Periodic Crystals and Quasicrystals in Ultrathin Films of Ba-Ti-O.
abstract: We model the remarkable thin-film Ba-Ti-O structures formed by heat treatment of an initial perovskite BaTiO3thin film on a Pt(111) surface. All structures contain a rumpled Ti-O network with all Ti threefold coordinated with O, and with Ba occupying the larger. mainly Ti7O7, pores. The quasicrystal structue is a simple decoration of three types of tiles: square, triangle and 30° rhombus, with edge lengths 6.85 Å, joined edge-to-edge in a quasicrystalline pattern; observed periodic crystals in ultrathin film Ba-Ti-O are built from these and other tiles. Simulated STM images reproduce the patterns seen experimentally, and identify the bright protrusions as Ba atoms. The models are consistent with all experimental observations.
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Cockayne
authors.affiliation: Institute of Physics, Slovak Academy of Sciences, 84511 Bratislava, Slovakia.
authors.forename: Marek
authors.initials: M
authors.lastname: Mihalkovič
authors.affiliation: Department of Physics, Cornell University, Ithaca, New York 14850 USA.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Henley