Surface segregation and chemisorption of CO and oxygen on Pt25Ni75(111) studied by XPS and 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. 331-333 (1995) 824-830

After sputtering and annealing to different temperatures TA the chemically disordered (111) surface of a Pt25Ni75 crystal exhibits a composition that depends strongly on TA. This has been already observed earlier by ion scattering and scanning tunneling microscopy [M. Schmid et al., Nucl. Instrum. Methods B82 (1993) 259]. To complement this work, we have used angle-resolved X-ray photoelectron spectroscopy (XPS) to investigate the segregation behaviour a few layers below the surface. We have also used high-resolution electron energy loss spectroscopy (HREELS) to study adsorbate vibrations of differently prepared surfaces of Pt25Ni75(111) after exposure to O2 and CO at room temperature.