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 24.61: Poster
Mittwoch, 26. März 2003, 14:30–17:30, P1
Interaction of CsCl with molecular surfaces (H2O; CH3OH; C2H5OH) — •A. Borodin, O. Höfft, U. Kahnert, and V. Kempter — Institut für Physik und Physikalische Technologien, Technische Universität Clausthal, Leibnizstr. 4 38678 Clausthal Zellerfeld
Molecular films (H2O, CH3OH, C2H5OH) were grown on tungsten and exposed to CsCl molecules under the No-dqin situNo-dq control of MIES and UPS. The electron spectroscopic results reveal that at 80K at least two stable positions for CsCl adsorption exist: (i) integration into the solvent films as Cs+ and Cl− solvated ions, and (ii) in front of the film. The interaction of CsCl with the film has the following consequences: (1) for H2O and CH3OH an ion-induced destruction of the hydrogen-bonded network takes place beyond a certain critical film stoichiometry (CsCl·6H2O for water as solvent), and (2) for C2H5OH there is an ion-induced reorientation of the solvent molecules. Upon heating the CsCl exposed film to about 120K, the on-top adsorbed species become embedded into the selvedge of the solvent film. This can be understood as being caused by a temperature-induced change of the solvent density profile and a concurrent change of the free energy profile of the adsorbed species. The solvent molecules desorb in the temperature range 140 to 160K; at higher temperatures only Cs and Cl species can be detected on the tungsten substrate and desorb around 400K.