Optical absorption in very thin dielectric films and its origin

Although the optical behavior of rather thick transparent dielectric films on metal surfaces can be accurately described by an idealized model considering the system as plane parallelsided homogeneous phases with a discontinuous boundary between them, deviations are encountered when the dielectric phase is thinner than 100 Å. Evidence is presented that there is anomalous absorption in the thin dielectric films. An explanation of this absorption in terms of the electric double layer is proposed.