title: Electron stimulated hydroxylation of a metal supported silicate film.
abstract: Water adsorption on a double-layer silicate film was studied by using infrared reflection-absorption spectroscopy, thermal desorption spectroscopy and scanning tunneling microscopy. Under vacuum conditions, small amounts of silanols (Si-OH) could only be formed upon deposition of an ice-like (amorphous solid water, ASW) film and subsequent heating to room temperature. Silanol coverage is considerably enhanced by low-energy electron irradiation of an ASW pre-covered silicate film. The degree of hydroxylation can be tuned by the irradiation parameters (beam energy, exposure) and the ASW film thickness. The results are consistent with a generally accepted picture that hydroxylation occurs through hydrolysis of siloxane (Si-O-Si) bonds in the silica network. Calculations using density functional theory show that this may happen on Si-O-Si bonds, which are either parallel (i.e., in the topmost silicate layer) or vertical to the film surface (i.e., connecting two silicate layers). In the latter case, the mechanism may additionally involve the reaction with a metal support underneath. The observed vibrational spectra are dominated by terminal silanol groups (ν(OD) band at 2763 cm(-1)) formed by hydrolysis of vertical Si-O-Si linkages. Film dehydroxylation fully occurs only upon heating to very high temperatures (∼ 1200 K) and is accompanied by substantial film restructuring, and even film dewetting upon cycling hydroxylation/dehydroxylation treatment.
authors.affiliation: Abteilung Chemische Physik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. shaikhutdinov@fhi-berlin.mpg.de.
authors.forename: Xin
authors.initials: X
authors.lastname: Yu
authors.affiliation: Abteilung Chemische Physik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. shaikhutdinov@fhi-berlin.mpg.de.
authors.forename: Emre
authors.initials: E
authors.lastname: Emmez
authors.affiliation: Abteilung Chemische Physik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. shaikhutdinov@fhi-berlin.mpg.de.
authors.forename: Qiushi
authors.initials: Q
authors.lastname: Pan
authors.affiliation: Abteilung Chemische Physik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. shaikhutdinov@fhi-berlin.mpg.de.
authors.forename: Bing
authors.initials: B
authors.lastname: Yang
authors.affiliation: Abteilung Chemische Physik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. shaikhutdinov@fhi-berlin.mpg.de and Institut für Physik, Universität Graz, Universitätsplatz 5, 8010 Graz, Austria.
authors.forename: Sascha
authors.initials: S
authors.lastname: Pomp
authors.affiliation: Abteilung Chemische Physik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. shaikhutdinov@fhi-berlin.mpg.de.
authors.forename: William E
authors.initials: WE
authors.lastname: Kaden
authors.affiliation: Abteilung Chemische Physik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. shaikhutdinov@fhi-berlin.mpg.de and Institut für Physik, Universität Graz, Universitätsplatz 5, 8010 Graz, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Sterrer
authors.affiliation: Abteilung Chemische Physik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. shaikhutdinov@fhi-berlin.mpg.de.
authors.forename: Shamil
authors.initials: S
authors.lastname: Shaikhutdinov
authors.affiliation: Abteilung Chemische Physik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. shaikhutdinov@fhi-berlin.mpg.de.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Freund
authors.affiliation: Institut für Chemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany. js@chemie.hu-berlin.de.
authors.forename: Itziar
authors.initials: I
authors.lastname: Goikoetxea
authors.affiliation: Institut für Chemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany. js@chemie.hu-berlin.de.
authors.forename: Radoslaw
authors.initials: R
authors.lastname: Wlodarczyk
authors.affiliation: Institut für Chemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany. js@chemie.hu-berlin.de.
authors.forename: Joachim
authors.initials: J
authors.lastname: Sauer