AVS 47th International Symposium
    Surface Science Thursday Sessions
       Session SS1+MC-ThM

Paper SS1+MC-ThM4
Oxidation of Sn/Pt (111) Surface Alloys under UHV Conditions- Formation of Ultrathin SnOx Films on Pt(111)

Thursday, October 5, 2000, 9:20 am, Room 208

Session: Oxide Applications and Oxidation
Presenter: B.E. Koel, University of Southern California
Authors: M. Batzill, University of Southern California
D. Beck, University of Southern California
B.E. Koel, University of Southern California
Correspondent: Click to Email
Platinum-tin systems are important as hydrocarbon reforming catalysts when supported on alumina. The tin may however exist in oxidic form and thus SnOx may be responsible for the altered catalytic properties of the Sn-Pt system compared to pure Pt, rather than alloying of Sn and Pt. In order to study ultrathin SnOx overlayers on Platinum we have oxidized both ordered Sn/Pt(111) surface alloys (the p(2x2) and the (sqr3 x sqr3)R30 alloy structure) using NO2 as an oxidant. The structure, chemical state and thermal stability of the oxide films have been examined by LEED, STM, XPS, AES and TPD. Oxidation of p(2x2) alloy results in a discontinuous mono-layer thick SnOx film that decomposes at 760 K. Oxidation of the (sqr3 x sqr3)R30 in contrast forms a thermally more stable continuous overlayer that shows two ordered surface phases depending on the annealing temperature. These structures have been analyzed using LEED and STM. The chemical activity of these surfaces was probed by small hydrocarbon molecules and CO.