Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 27: Metal subtrates: Adsorption of O and/or H
O 27.7: Vortrag
Dienstag, 23. März 2010, 12:00–12:15, H42
The molecular structure of ice on Pt(111) — •Sebastian Standop1, Alex Redinger1, Markus Morgenstern2, Thomas Michely1, and Carsten Busse1 — 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln — 2II. Physikalisches Institut (IIB), RWTH Aachen, D-52056 Aachen
Using Scanning Tunneling Microscopy the molecular arrangement of the wetting layer of H2O on Pt(111) is resolved. The water molecules arrange in a hexagonal pattern resembling the (0001) surface of ice Ih. The dense packed molecular rows are slightly rotated with respect to the dense packed rows of the underlying metal. This leads to a complex superstructure in accordance with scattering experiments [1]. Due to the tendency of single water molecules to adsorb flat on Pt(111) the structure is geometrically frustrated as each monomer donates two hydrogen bonds but can in turn accept only one. The system escapes this frustration by the introduction of a disordered arrangement of vacancy clusters.
Our results show that the degree of order in the globally disordered phase may be increased artificially. On an appropriate substrate both the √39 × √39 R16.1∘ structure for a full monolayer as well as the √37 × √37 R25.3∘ structure for submonolayer water islands could be identified. Based on the well known binding mechanism of single molecules we propose criteria for the structure formation, domain size enhancement and thermodynamic stability of these high order commensurate phases.
[1] A. Glebov et al., Journal of Chemical Physics 106 (1997) 9382