IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM10
Water Reactivity with MgO(100)Thin Film Surfaces Studied by Electron Stimulated Desorption

Tuesday, October 30, 2001, 11:20 am, Room 122

Session: Water at Surfaces
Presenter: J.L. de Segovia, CSIC, Spain
Authors: D. Cáceres, Universidad Carlos III de Madrid, Spain
I. Colera, Universidad Carlos III de Madrid, Spain
I. Vergara, Universidad Carlos III de Madrid, Spain
R. González, Universidad Carlos III de Madrid, Spain
E.L. Román, CSIC, Spain
J.L. de Segovia, CSIC, Spain
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The adsorption of two isotopic forms of water, D@sub 2@ @super 16@O and H@sub 2@ @super 18@O, with well characterised MgO(100) thin film surfaces at 300 K was studied by Electron Stimulated Desorption, ESD. Oriented MgO(100) thin films were grown on Si(100) at 940 K by rf-sputtering with a Mg target and at a total pressure of 7 x 10@super -3@ mbar (10% O@sub 2@ and 90% Ar). These films were characterized by X-Ray diffraction, Auger Electron Spectroscopy (AES), X-Ray Photoelectron Spectroscopy (XPS), and Electron Energy Loss Spectroscopy (EELS). Previous ESD results@footnote 1,2@ of O@super +@ desorbed species from clean surfaces of bulk MgO(100) showed a bimodal energy distribution structure with peaks at 6 and 9 eV. Their origin was assigned to O@super +@ desorption from surface defects and to desorption from the oxide, respectively. The aim of the present ESD study of MgO(100) thin films is twofold: (i) to compare the previous results on bulk defective surfaces (stepped or with oxygen vacancies) with a thin film surface with no steps, and (ii) to study the reactivity of water with these thin films, and the influence of surface defects on the hydrolisis processes. D and @super 18@O isotopes were used to distinguish them from the H contamitation and from the @super 16@O of the oxide, respectively. Ion yield experiments using H@sub 2@ @super 18@O show @super 18@O@super +@ and @super 18@OH@super +@ desorbed ions in addition to the usual H@super +@ and @super 16@O@super +@ ions. The adsorption of @super 18@O is related to the @super 16@O defective sites on the MgO(100) thin films. Preliminary results indicate that the Feibelman-Knotek mechanism is responsible for the desorption processes. Ion kinetic distribution curves at different electron energies are also discussed. @FootnoteText@@footnote 1@ I. Colera, E. Soria, E. Rom@aa a@n and R. Gonz@aa a@lez, Vacuum 48 nº 7-9 pag 647 to 649 (1997) @footnote 2@ I. Colera, R. González, E. Soria, J.L. de Segovia, E.L. Román and Y. Chen, J. Vac. Sci. Technol. A 15(3) pag 1698-1703 (1997).