COMPOSITE EFFECTS IN THE ELECTRONIC-STRUCTURE OF AU-PD AND AG-PD

The understanding of the electronic structure of disordered alloys and bimetallic systems is not yet as advanced as that of ordered crystals. Spectroscopic optical conductivity measurements provide the most direct method for determining the electronic properties of the disordered systems and impurity states. In this paper we present preliminary studies of changes in the electronic structure of host metals during diffusion of Pd atoms through thin films of Au and Ag. The samples were prepared by evaporation of about 200 nm thick films of Au and Ag onto pure Pd foils. The influence of transition metal atoms, located in the grain boundaries and inside of noble metal grains, on the optical properties of the systems has been investigated by means of spectroscopic ellipsometry, in the photon energy range 1.65-3.1 eV. The experimental results are qualitatively interpreted on the basis of an effective medium composite microstructure and the virtual-bound-state model, which applies to the diluted transition-noble-metal alloys.