Surface composition of Pt25Ni75(111) probed by HREELS

A. Pantförder, J. Skonieczny, E. Janssen, G. Meister, A. Goldmann, and P. Varga*

Fachbereich Physik, Universität GH Kassel, D-34132 Kassel, Germany
*Institut für Allgemeine Physik, Technische Universität Wien, A-1040 Wien, Austria

Surf. Sci. 337 (1995) 177-182

High-resolution electron energy loss spectroscopy (HREELS) has been used to study vibrations of CO molecules chemisorbed at low coverage on a Pt25Ni75 sample after different surface treatments. In agreement with earlier work using other methods, we always observe that Pt is enriched in the outermost layer, with a chemical composition strongly dependent on the annealing temperature. We discuss to which extent HREELS of CO may be exploited to "titrate" the surface composition of binary alloys.