Valence band structure of monolayer alloy films of copper and gold on Ru(0001)

The valence bands of monolayer alloy films of Au and Cu grown on a single crystal Ru(0001) substrate were monitored using Angle-Resolved Photoemission Spectroscopy (ARUPS). A surface state was observed near the K-point for each of the alloy film samples. Using extended Huckel tight-binding calculations to model the composite film-substrate interaction, the state is identified as an interfacial surface state, having character on both the Cu-Au film and the first layer of Ru. Although evidence of long range order was not observed by LEED, certain spectral features between the main Cu and Au peaks are indicative of local ordering.