Core-level shifts in trimetallic systems

Trimetallic systems prepared by the deposition of monolayers of two different metals (Cu, Pd, Ag, and Au) on a Mo(110) single crystal have been studied using x-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS). Because the dissimilar second layer can be resolved from the bulk substrate with XPS, this approach allows the core-level shifts (CLSs) for the first and second layers in the trimetallic system to be measured. ISS was employed to measure the relative surface composition of the sample in order to identify those systems in which no significant mixing of the admetals takes place at room temperature. The Cu/Pd/Mo(110), Au/Pd/Mo(110), and Ag/Cu/Mo(110) systems were determined to exist as segregated monolayers at room temperature. Initial ISS studies showed that a He+ ion beam with an energy of 475 eV was sufficient to induce alloying between Cu and Pd monolayers. The CLSs for the Au/Pd/Mo(110) and Cu/Pd/Mo(110) systems indicate changes in the d-electron populations of Au, Pd, and Cu. In the case of the Cu/Pd/Mo(110), the CLSs cannot be explained in terms of a simple charge transfer between metals. copyright 1995 American Vacuum Society