The medium-related optical constants of noble metals observed by ellipsometric study

The optical constants used in metallic multilayer structures may differ from those measured in air using a two-phase model and thus will affect the design performance of an optical device. To understand the effect better, we used Dove prisms with different refractive indices as the substrates. The spectroscopic ellipsometry method was used to measure directly the optical constants of Ag and Au films which were thermally or electron-beam evaporated on the bottom of the prisms. In this configuration, the optical constants of the films can be measured at the metal-air and metal-substrate interfaces. Upon data reduction, we found that the optical constants of a given film measured at the metal-substrate interface do change with the refractive index of the substrate and differ from those measured at the metal-air interface in both of the Drude and interband transition regions. These results agree with those obtained by other authors in a liquid-contacting situation, and need to be studied in great detail in the future. (C) 1998 Elsevier Science S.A.