'Transparent' metal films: Experiment and theory.

We have made essentially transparent metal films up to 300angstroms thick by photoelectrochemical deposition of platinum onto p-type indium phosphide. Here, we report the optical characteristics of these films, and show how near-transparency can be achieved when the metallic films are porous and when they are built up of particles which are smaller than the wavelength of the transmitted light. The minimization of light reflection and absorption by metallic films having the required microstructure can be understood in terms of effective medium theory. Dielectric optimization of metal films through control of their microstructure is also discussed.