Anomalous optical constants of thin films

The explanation of anomalous optical constants in thin chemically distinct layers on substrates offered by Plumb is re-examined and extended. The model invokes the concept of the space charged boundary layer and treats the charge carrier population as a free-electron gas to derive the optical behaviour of thin surface films. The implication of the space charge means that the optical constants of a dielectric film on a metal will vary over a distance directly proportional to the dielectric constant of the film and inversly proportional to the concentration of the electrons at the metal/film interface. Similarly as the temperature increases this space charge region should extend to larger distances from the interface.