Hamburg 2001 – wissenschaftliches Programm
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O: Oberflächenphysik
O 13: Postersitzung (Adsorption auf Oberfl
ächen, Oberfl
ächenreaktionen, Elektronische Struktur, Epitaxie und Wachstum, Halbleiteroberfl
ächen und Grenzfl
ächen, Oxide und Isolatoren)
O 13.24: Poster
Montag, 26. März 2001, 19:00–22:00, Foyer zu B
Reaction of sulfur and oxygen on Ir(110): Activation by compression of coadsorbed phases? — •Jens Kuntze1, Sylvia Speller2, and Werner Heiland2 — 1Institut für Experimentelle und Angewandte Physik der Universität Kiel, D-24098 Kiel — 2Universität Osnabrück, FB Physik, D-49069 Osnabrück
We investigated the structural aspects of the adsorption and coadsorption of oxygen and sulfur on Ir(110) by scanning tunneling microscopy (STM). When sulfur is adsorbed on the Ir(110) surface, S atoms do not coalesce to larger islands due to repulsive interaction. However, as oxygen is coadsorbed, two regimes of coadsorbate induced compression can be distinguished: At low O coverages, the S Atoms coalesce to form a p(2×2)-2S phase indicating competitive adsorption. Further oxygen adsorption leads to a decomposition of this structure towards a disordered S-O phase. Interestingly, Auger spectra taken before and after annealing indicate that only one of the two coadsorption phases seems to be reactive: The sulfur Auger signal decreases significantly upon annealing the disordered phase, whereas the ordered coadsorption structure seems non-reactive. The increased O-O repulsion in the disordered phase is suggested to be responsible for this activation effect.