SURFACE-STRUCTURE DETERMINATION OF SN DEPOSITED ON PT(111) BY LOW-ENERGY ALKALI ION-SCATTERING

Surface structures resulting from the deposition and annealing of Sn on Pt(111) and exhibiting p(2 x 2) and p(square-root 3 x square-root 3)-R30-degrees LEED patterns have been studied by low energy alkali ion scattering. Azimuthal and polar incident angle dependencies were measured for 500 and 1000 eV Li+ ions scattered from the clean and Sn covered surfaces. Shadowing and blocking effects adequately describe the single scattering from the clean Pt surface. The data support a structural model in which the Sn is incorporated into the Pt surface rather than existing as an overlayer. Analysis of the Sn angle dependence indicates that the Sn is not coplanar with the Pt but is protruding 0.022 +/- 0.005 nm above the surface. The results are compared with related metal-on-metal systems.