Optical properties of thin film Au-MgF2 cermets

The preparation of thin films of cermets of gold in magnesium fluoride and the ellipsometric determination of the optical constants of the materials of the films are described. The results for materials of two compositions are compared with predictions based on the Maxwell Garnett expression for the complex refractive index of cermets in terms of the refractive indices of the constituents. It is shown that reasonable agreement between experimentally determined and theoretical values of the refractive indices of the cermets can be approached only if the restriction of the mean free paths of the conduction electrons in the gold particles is taken into account.