AVS 53rd International Symposium
    Surface Science Thursday Sessions
       Session SS1-ThA

Paper SS1-ThA1
Effect of Pt on Clean and Oxidized Surfaces of (Ni, Pt)@sub3@Al

Thursday, November 16, 2006, 2:00 pm, Room 2002

Session: Reactivity of Oxide Surfaces II
Presenter: F. Qin, Iowa State University
Authors: F. Qin, Iowa State University
J.W. Anderegg, Ames Laboratory
C.J. Jenks, Ames Laboratory
C. Jiang, Iowa State University
B. Gleeson, Iowa State University
D.J. Sordelet, Ames Laboratory
P.A. Thiel, Iowa State University
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We have used experimental techniques (XPS, AES, LEED LEIS and STM) and a theoretical technique (DFT) to investigate the clean and oxidized surfaces of ternary (Ni, Pt)@sub3@Al single crystals. Regarding the clean surface, our experiment results indicate that Pt segregates to the surface. Density functional calculations in the dilute limit confirm that Pt segregation is favored energetically. Regarding the oxidized surface, we systematically examined the amount, chemical nature, and spatial distribution of the oxide that forms upon saturation at oxygen pressures in the range of 10@super-8@ to 10@super-6@ Torr, as a function of oxidation temperatures (300 to 900 K) and as a function of Pt content. We found that the predominant oxide between about 300 and 700 K is NiO, covered by a thin top layer of aluminum oxide, whereas between 700 and 900 K the predominant oxide is aluminum oxide. Pt exerts four effects: (a) Pt decreases the maximum amount of NiO; (b) Pt shifts formation of Al@subx@O@suby@ to lower temperatures; (c) Pt decreases the maximum amount of Al@subx@O@suby@; and (d) Pt slows the oxygen adsorption on the clean surface.