Complete unambiguous optical characterization of double layers consisting of two strongly absorbing thin films by combined reflection and transmission ellipsometry.

A new ellipsometric method for the complete unambiguous optical characterization of double layers consisting of two strongly absorbing thin films placed on a nonabsorbing substrate is described in this paper. The method utilizes simultaneous interpretation of ellipsometric parameters measured for light reflected and transmitted by the ambient side and the substrate side of the two samples of the double layer investigated. These samples must have different thicknesses of both strongly absorbing films (at least the thickness of one of the two films). The method was successfully employed for analyzing the double layers formed by gold and chromium films at a wavelength of 632.8 nm.