Electronic structure ofCu75Au25disordered alloy

We present angle-resolved uv photoemission (normal emission) measurements from the (100) and (111) surfaces of ${\mathrm{Cu}}_{75}$ ${\mathrm{Au}}_{25}$ alloy single crystals, together with fully relativistic as well as nonrelativistic Korringa-Kohn-Rostoker coherent-potential-approximation calculations of complex energy bands and densities of states. A good overall accord is found between the measurements and theoretical predictions with regard to the shifts and smearings of various bulk states in the alloy. The characteristic effects of alloying Au on the electronic structure of Cu are identified; the principal Au-induced feature is 2.5 eV wide, and appears 3 eV below the Cu-derived d band in the alloy; this feature is split into two distinct peaks, approximately 1.4 eV apart, due to relativistic spin-orbit interaction. The (111) Shockley surface state is observed to shift by 80 meV towards the Fermi energy in the alloy, and to suffer an increased broadening (full width at half maximum) of 140 meV compared with Cu.