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Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 40: Oxides and insulators

O 40.4: Talk

Thursday, March 30, 2006, 15:45–16:00, WIL A317

Ordered alumina film on NiAl(110): Structure of the antiphase domain boundaries and of metallic clusters — •Evelyn Napetschnig1, Michael Schmid1, Georg Kresse2, Lukas Köhler2, Maxim Shiskin2, and Peter Varga11Institut f. Allgemeine Physik, Vienna University of Technology, Austria — 2Institut fuer Materialphysik, University of Vienna, Austria

Transition metal clusters on alumina support are one of the most frequently used model systems for investigations of heterogenous catalysis. When NiAl(110) is oxidized at elevated temperatures an alumina film of uniform thickness and structure [1,2] with a network of domain boundaries is formed. The domain boundaries act as nucleation centers for metal clusters. We could determine the structure of the antiphase domain boundary by combining STM images and density-functional theory calculations [3]. Our measurements of the morphology of Co, Pd and bimetallic Co-Pd clusters on the alumia film show that for Pd and Co non- crystalline clusters with a steep slope and a round top are thermodynamically favourably. For the bimetallic Pd-Co clusters we proof that Pd is covering pre-deposited Co clusters like a shell whereas for deposition in the reverse order Pd is segregating to the cluster*s surface and intermixes with the added Co.

[1] M. Bäumer and H.J. Freund, Prog. Surf. Sci. 61 (1999) 127

[2] G. Kresse M.Schmid, E.Napetschnig, M.Shishkin, L.Köhler and P.Varga, Science 308 (2005) 1440

[3] M. Schmid, G. Kresse, M. Shishkin, E.Napetschnig, M. Kulawik, N. Nilius, H.J. Freund and P. Varga, to be published

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