The measurement of the roughness of W/Si multilayers using the Fresnel method

The application of the Fresnel Method for the determination of the roughness of sputtered multilayers of W/Si, as used for X-ray mirrors, is examined. This particular usage of the approach is complicated both by the large differences in the scattering potential and absorption of the constituents of the respective layers and by difficulties in determining the thickness of an edge-on foil of the layered structure. The ways in which these problems can be overcome are described, as is the typical compositional roughness of layered structures of this system.