Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 28: Adsorption an Oberfl
ächen III
O 28.8: Vortrag
Donnerstag, 27. März 2003, 13:00–13:15, FOE/ANOR
Oxygen-driven transport of Ag on Ag/W(110) — •C. Deisl1, K. Swamy1, E. Bertel1, M. Bürgener2, W. Holzapfel2, G. Meister2, and A. Goldmann2 — 1Institut für Physikalische Chemie, Universität Innsbruck — 2Experimentalphysik II, Universität Kassel
The structural changes of Ag films on W(110) upon coadsorption of oxygen
have been studied by Scanning Tunnelling Microscopy (STM), valence band
(UPS) and core level photoemission (XPS).
The exposure of one monolayer Ag to oxygen leads to a phase separation into
an Ag bilayer and patches of O-covered W(110).
The effective Ag island thickness increases linearly with oxygen exposure.
For Ag submonolayer-islands the onset of the bilayer formation is delayed.
The induction period increases with the available free W area.
We
conclude that the steps of the transport process are:
(i) Dissociation
of oxygen on W and on the Ag islands. (ii) Site exchange of atomic oxygen
with Ag atoms on the silver islands, while on the W(110) the oxygen is
immobile. (iii) Diffusion of the displaced Ag atoms to the island edges
where they are incorporated into the monolayer.
(IV) Initiation of Ag bilayer formation, once the W(110) is saturated with
O.
This indicates an unexpected activity of the Ag monolayer on W(110) towards
oxygen dissociation.