AVS 47th International Symposium
    Thin Films Wednesday Sessions
       Session TF+EL-WeA

Paper TF+EL-WeA4
Growth of Oxygen-rich Films on Ru(0001)

Wednesday, October 4, 2000, 3:00 pm, Room 203

Session: In-situ Characterization of Thin Film Growth
Presenter: A. Böttcher, Fritz-Haber-Institut, Germany
Authors: A. Böttcher, Fritz-Haber-Institut, Germany
B. Krenzer, Fritz-Haber-Institut, Germany
W. Stenzel, Fritz-Haber-Institut, Germany
H. Conrad, Fritz-Haber-Institut, Germany
H. Niehus, Humboldt-Universität, Germany
Correspondent: Click to Email
The potential of photoemission electron microscopy (PEEM) has been utilized for monitoring the modifications of Ru(0001) induced by surface oxidation. The PEEM images of the initial oxidation stages exhibit bright patterns appearing on dark background. The former represent the precursor phases of regular oxides, Ru@sub x@O@sub y@. The background reflect the termination of the Ru(0001) surface by the chemisorbed oxygen layer. The growth of the Ru@sub x@O@sub y@ from nucleation centers to a thick oxide film strongly depends on the oxidation temperature. Three phases differing by characteristic morphologies have been distinguished. For low temperatures, TT@sub H@, the Ru@sub x@O@sub y@ phase manifests itself by very bright discs randomly distributed over large dark areas. For moderate temperatures, T@sub H@>T>T@sub L@, long stripes appear and grow along the main crystallographic directions of Ru(0001). This growth is initiated by formation of light grains. Further oxidation proceeds via a growth of star-shaped and linear islands following the hexagonal symmetry of the substrate and leads finally to the formation of an ordered network. The growth modes result from destabilization of the Ru surface.@footnote 1@ The thick oxygen-rich films created under low- and moderate-temperature oxidation regime are thermally unstable. PEEM images become gradually dark when keeping the sample at temperatures higher than the oxidation temperature. This transformation reveals the cluster formation of stoichiometric oxides as well as a rearrangement of Ru and O atoms across the thick oxygen-rich layer. All mesoscopic-scale structures studied offer adsorption sites for surplus atomic oxygen adsorbed when exposing them to oxygen at room temperature. @FootnoteText@ @footnote 1@A. Böttcher, H. Conrad, H. Niehus, J. Chem. Phys. 112 (2000) 4779.