Optical properties of extremely thin films: studies using ATR techniques.

The optical constants and optical properties of extremely thin ZnS, SiO(2), Al, and Ag films are studied and compared by attenuated total reflection (ATR) techniques. The optical constants and optical absorptance as a function of film thickness are measured. The experimental results agree well with theoretical prediction. It is found that there is no discontinuity in optical constants and absorptance when an extremely thin layer changes from isolated islands to a continuous film for all the measured materials. The critical thicknesses at which they form continuous films show great differences for the various materials and deposition methods. The dependence of absorptance on thickness of extremely thin layers is studied experimentally and theoretically.