Optical properties of ultrathin Pd and Pt films on a quartz substrate and on tungsten trioxide films

Based on ellipsometry and transmission spectra, optical parameters of palladium and platinum films were determined. The Pd and Pt films had a thickness of 5 – 7 nm and were studied both on a SiO2 and WO3 substrates. Despite the extremely small thicknesses, the parameters of most films were well described by isotropic dielectric constant. An interesting feature was that films deposited directly on a SiO2 substrate had a positive (rather than negative, characteristic of a metal) real part of the effective dielectric constant, while the films deposited on WO3 exhibited metallic properties for unannealed films and properties characteristic of metal-dielectric composites for films that have been annealed (some of the films annealed at 300°C in argon retained their metallic properties).