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 24.49: Poster

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

The interaction of carbon monoxide with bimetallic gold/rhenium(0001)surfaces — •Astrid Weingart and Klaus Christmann — Institut für Chemie, Physikalische und Theoretische Chemie, FU-Berlin, Takustr.3, 14195 Berlin

The interaction of CO with a Re(0001) surface decorated with gold atoms in the submonolayer range was studied between 100 K and 270 K by means of thermal desorption (TDS), LEED, and work function ( ΔΦ ) measurements. On clean Re(0001), CO produces three thermal desorption states ( α₁ , α₂ and β (the latter at elevated temperatures) attributed to molecularly adsorbed CO ( α -states) and to dissociated CO molecules ( β -state). Even very small Au pre-coverages ( Θ_Au = 0.2ML ) completely suppress the β -state indicating that Au passivates rhenium’s activity for CO dissociation. On the other hand, CO exposure of the bimetallic surface at 100 K causes population of two additional CO TD-states at 140 K and 197 K, which are associated with occupation of mixed Au/Re-sites. Increasing Au coverages make the maximum of the TD-signals shift to lower temperatures. Measurements of the CO-induced ΔΦ at 100 K reveal a clear work function decrease for the bimetallic Au/Re as compared to bare Re(0001). Our results are discussed and compared with previous findings on bimetallic Au/Ru surfaces.