AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP33
Epitaxial Iron Oxide Growth on Vicinal Pt(111): Well-defined Defective Model Systems?

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: G. Ketteler, Lawrence Berkeley National Laboratory, University of California
Authors: G. Ketteler, Lawrence Berkeley National Laboratory, University of California
W. Ranke, Fritz-Haber-Institute of the MPG, Germany
Correspondent: Click to Email
Heterogeneous catalysts consist often of metals in contact with oxides and the activity depends on the interaction between them. In addition, the defect structure of the surface is of high importance for the catalytic activity. The common electron-based surface science techniques allow the characterization of model catalyst surfaces with atomic precision. Studied model catalyst systems include single crystal surfaces, epitaxial compound films, or well-defined particles deposited on single-crystalline supports. However, real catalysts contain a defect structure which is difficult to model in a well-defined manner. In order to study the controlled introduction of defects into iron oxide model catalysts for the dehydrogenation of ethylbenzene to styrene, we have grown different iron oxide phases on a stepped Pt(9 11 11) single crystal surface and characterized the film structures by STM and high-resolution SPA-LEED measurements. The hope was that this may provide a way to introduce well-defined step defects into the epitaxially grown films. For coverages below 1 ML, FeO(111) films wet the vicinal Pt substrate. The step structure changes under formation of doubled and triplicated terrace widths and step heights. Further cycles of iron deposition and oxidation lead to a Stranski-Krastanov-type growth of Fe@sub 3@O@sub 4@(111) islands which initially are elongated along the edge direction. However, the morphology of a coalesced closed film is almost unaffected by the underlying substrate step morphology. High pressure oxidation of Fe@sub 3@O@sub 4@ films results in poorly defined Fe@sub 2@O@sub 3@(0001). Although FeO films grown on the vicinal Pt surface may serve as model systems for systematic studies of well-defined defective oxide surfaces, the catalytically more relevant Fe@sub 3@O@sub 4@ and Fe@sub 2@O@sub 3@ phases could not be obtained reproducibly with a well-defined defect structure.