Optical diagnostics of nanoscale dielectric layers on interference films by polarization-dependent differential reflectivity

The small change in the reflectance (differential reflectance) of s- or p-polarized light from an interference film as a result of the deposition of a nanoscale insulating layer on it is investigated theoretically. Analytical relations describing the contribution of nanoscale layers to the reflectance from an interference film as function of film thickness are obtained in the long-wavelength approximation. It is shown that the utilization of interference films in reflection diagnostics through differential measurements allows a significant enhancement of the sensitivity of these techniques and also opens up new possibilities for resolving the inverse problem of determining simultaneously the optical constant and thickness of nanoscale dielectric layers.