Infrared absorption of granular metal films in the percolation range

Experimental optical absorption of gold granular films near the percolation threshold are compared with a two dimensional simulation using a real space renormalization procedure. It is some times asserted that the optical properties around the percolation cannot be described by an effective dielectric function, but we obtain good agreement between the simulations and the experimental data. According to this approach, the IR absorption is attributed to the surface plasmon modes broadened toward IR wavelengths due to the fractal nature of the clusters.