title: In situ scanning tunneling microscopy study of Ca-modified rutile TiO2(110) in bulk water.
abstract: Despite the rising technological interest in the use of calcium-modified TiO2 surfaces in biomedical implants, the Ca/TiO2 interface has not been studied in an aqueous environment. This investigation is the first report on the use of in situ scanning tunneling microscopy (STM) to study calcium-modified rutile TiO2(110) surfaces immersed in high purity water. The TiO2 surface was prepared under ultrahigh vacuum (UHV) with repeated sputtering/annealing cycles. Low energy electron diffraction (LEED) analysis shows a pattern typical for the surface segregation of calcium, which is present as an impurity on the TiO2 bulk. In situ STM images of the surface in bulk water exhibit one-dimensional rows of segregated calcium regularly aligned with the [001] crystal direction. The in situ-characterized morphology and structure of this Ca-modified TiO2 surface are discussed and compared with UHV-STM results from the literature. Prolonged immersion (two days) in the liquid leads to degradation of the overlayer, resulting in a disordered surface. X-ray photoelectron spectroscopy, performed after immersion in water, confirms the presence of calcium.
authors.affiliation: Department of Physics, Università degli Studi di Roma "Tor Vergata", Via della Ricerca Scientifica 1, 00133 Rome, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Serrano
authors.affiliation: Department of Physics, Università degli Studi di Roma "Tor Vergata", Via della Ricerca Scientifica 1, 00133 Rome, Italy.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Bonanni
authors.affiliation: Department of Physics, Università degli Studi di Roma "Tor Vergata", Via della Ricerca Scientifica 1, 00133 Rome, Italy ; Institut für Physikalische und Theoretische Chemie, Wegelerstraße 12, 53115 Bonn, Germany.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Kosmala
authors.affiliation: Department of Physics, Università degli Studi di Roma "Tor Vergata", Via della Ricerca Scientifica 1, 00133 Rome, Italy ; Istituto di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche (CNR), Via Fosso del Cavaliere 100, 00133 Rome, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Di Giovannantonio
authors.affiliation: Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Diebold
authors.affiliation: Institut für Physikalische und Theoretische Chemie, Wegelerstraße 12, 53115 Bonn, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Wandelt
authors.affiliation: Department of Physics, Università degli Studi di Roma "Tor Vergata", Via della Ricerca Scientifica 1, 00133 Rome, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Goletti
keywords: alkali earth metals; scanning probe microscopy; solid/liquid interface; titanium dioxide reconstruction
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