Characterization of gold films by surface plasmon spectroscopy: Large errors and small consequences

Evaporated gold films have a smooth interface with their substrate and a rougher top surface. We investigate the optical response of such a film by excitation of surface plasmons both on the rough and on the smooth side. The smooth side, although polycrystalline, has an optical response that is very similar to a monocrystalline surface. The film can be modeled as two-layers with significantly different optical constants. For investigations on thin dielectric films though, this heterogeneity introduces only a negligible error.