Optical properties of silver-palladium alloys

Abstract

Thin films of Ag rich Ag-Pd alloys are prepared by cathodic sputtering. Reflectivity of pure metals and alloys is measured using four monochromators to successively cover the whole energy range between 0.1 and 90 eV. Optical and dielectric constants are deduced by a Kramers-Kronig analysis. It is obvious for the results obtained on Ag rich Ag-Pd alloys in the 1-6 eV energy range, that the virtual bound state model is appropriate for describing the alloy density of state. The virtual bound state is found to be centred at 2.35 eV below the Fermi level; the halfwidth of the states due to s-d interaction is equal to delta ⁰_sd=0.2 eV. The interactions between Pd d states gives an important contribution to the observed width. When the palladium concentration reaches 45 at.% the Pd d states form a true band; Friedel's theory therefore seems limited to the noble metal rich alloys.