AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS-TuP

Paper SS-TuP4
Adsorption of O@sub 2@ on Al(111) - No Evidence for "Hot Adatoms"

Tuesday, October 26, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: P. Varga, Technische Universität Wien, Austria
Authors: M. Schmid, Technische Universität Wien, Austria
P. Varga, Technische Universität Wien, Austria
Correspondent: Click to Email
Based on a scanning tunneling microscopy (STM) study,@footnote 1@ it has been suggested that adsorption of O@sub 2@ on Al(111) results in a high transient mobility of the two oxygen atoms created by dissociation of the oxygen molecule. It was suggested that these atoms move at least 80 Å apart before they come to rest at the surface.@footnote 1@ We have performed experiments under the same conditions. High-resolution STM images enable us to identify the features considered single O adatoms in ref. 1 as two O atoms in adjacent fcc hollow sites. We also find groups of three and four oxygen atoms, however. The dynamics of the O dimers point to an attractive interaction of O atoms in adjacent fcc hollow sites. These findings do not completely rule out the possibility of a large transient mobility and subsequent diffusion of individual O atoms, finally forming stable dimers. We consider it more likely, however, that only few O@sub 2@ molecules do not stay in adjacent hollow sites during adsorption and the single O adatoms created thereby diffuse until they coalesce with one of the dimers or larger O groups on the surface. With decreasing tunneling distance, Al atoms with three and two O neighbours appear as protrusions, explaining images with protrusions earlier attributed to single O adatoms. @FootnoteText@ @footnote 1@H. Brune et al., Phys. Rev. Lett. 68, 624 (1992); J. Chem. Phys. 99, 218 (1993).