STUDIES OF SURFACE-COMPOSITION AND STRUCTURE OF CU3PT(111) BY LOW-ENERGY ALKALI ION-SCATTERING

The composition and structure of the Cu3Pt(111) surface have been investigated by low energy alkali ion scattering. The surface composition of the top two layers was determined by Li+ ion scattering using selective scattering geometries with calibration measurements on reference samples of Cu(111) and Pt(111). Under thermal equilibrium conditions, these results consistently showed a surface composition of 80%Cu-20%Pt in the first layer, while the second layer was 69%Cu-31%Pt. The surface structure was probed by measuring the intensity of Li+ ion scattering as a function of incident angle along the main azimuthal directions. The interpretation of experimental data was based on a chain model simulation. The results showed that the Pt atoms were coplanar with the Cu atoms in the first layer. A clustering effect of Pt has also been tested using 1 keV K+ ion scattering. The results revealed that the Pt atoms in the first layer were not clustered by lack of the Pt-Pt pair double scattering peak along the two long azimuthal directions.