Photoelectron diffraction studies of Cu on Pd(111) random surface alloys

The study of surface alloys is motivated by their use in many applications of different segments of industry, such as in the search for new catalysts and sensors, in surface protection against corrosion, in lowering friction, and in testing electronic devices. An important aspect of surface alloys studies is that of the precise quantification of segregation and diffusion processes as well as the determination of surface structure. In this paper we report a combined low-energy electron diffraction and photoelectron diffraction (PED) (using synchrotron radiation) study of surface alloy formation when Cu ultrathin films are evaporated onto Pd(111) single-crystal surfaces. We present results for two different coverages (1 and 3 ML) and three annealing temperatures (300, 600, and 800 K). For these preparation conditions, a random alloy phase with different concentrations seems to form in the first few layers. Through the analysis of PED data performed using a multiple scattering formalism and the average T-matrix approximation it was possible to determine the atomic structure and the atomic concentration of the first three layers.