Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 24: Postersitzung (Epitaxie und Wachstum, Oxide und Isolatoren, Elektronische Struktur, Oberfl
ächenreaktionen, Adsorption an Oberfl
ächen, Organische Dünnschichten)

O 24.52: Poster

Mittwoch, 26. März 2003, 14:30–17:30, P1

Interaction of water with the BaF₂(111) surface: indications for dissociative adsorption from helium atom scattering experiments — •Jochen Vogt and Helmut Weiss — Chemisches Institut der Universität Magdeburg, Abteilung Physikalische Chemie, Universitätsplatz 2, 39106 Magdeburg

Fluorites like BaF₂ are widely used as basic materials for optical components and have therefore achieved considerable technical importance. Because of the small lattice mismatch of its (111) surface with H₂O ice, the possible relevance of BaF₂ for ice nucleation is e.g. discussed in context with the physics of the atmosphere [1]. While from HAS experiments an ordered (1×1) lattice was deduced for the 2D phase H₂O/BaF₂(111) at temperatures around 150 K and attributed to molecular adsorption [2], signs of a slow hydroxylation of the surface had been identified in XPS spectra [3]. We report on experiments in which by means of helium atom scattering the slow formation of a (√3×√3)R30^∘ lattice was observed for the first time. Taking into account the observability of this new phase at room temperature, we discuss its possible assignment to chemisorbed species on the BaF₂ surface.

[1] V. Sadtchenko et al., J. Chem. Phys. 116 (2002) 4293

[2] A. Lehmann et al., Surf. Sci. 369 (1996) 289

[3] Y. Wu et al., Langmuir 10 (1994) 1482