CO CHEMISORPTION ON PDCU(110) - A WORK FUNCTION STUDY

The work function change (Delta Phi) that occurs upon CO chemisorption on PdCu(110) single crystal was studied using the Kelvin probe techni que. The Delta Phi measurements were carried out for various surface c ompositions ranging from 100% Pd to 100% Cu, which were prepared by sp uttering and annealing the sample at different conditions. Auger Elect ron Spectroscopy (AES) and Thermal Desorption Spectroscopy (TDS) were used to characterise the surface before and after each Delta Phi measu rement. The results obtained in this study prove that the Delta Phi te chnique is very sensitive to changes in surface composition and can be therefore successfully used to determine quantitatively the top layer composition of PdCu(110) single crystal alloy. The Delta Phi results reported here indicate a charge transfer from Pd to Cu in PdCu alloys. As a result of this transfer process, the back donation of electrons from Pd to adsorbed CO is reduced and the dipole moment of adsorbed CO on Pd becomes smaller. (C) 1997 Published by Elsevier Science Ltd.