Bulk and Surface Effects in Photoemission from Disordered Cu -Ni Alloys

We report a synchrotron-radiation study of angle-resolved photoemission from single crystals of the random alloy Cu-40%-Ni, combined with first-principles Korringa-Kohn-Rostoker coherent-potential-approximation photocurrent calculations. We find that the intensity of emission from the Ni d states, relative to that from the Cu d states, reveals the →k and energy dependence of the disorder broadening of the electron states. Our results indicate that the surface composition profile is monotonic and not, as previously reported, oscillatory.