STRUCTURAL PARAMETERS OF MULTILAYERS FROM X-RAY REFLECTIVITY - AN EASY-TO-HANDLE APPROACH

An analytical approximation was derived for the calculation of the gra zing-incidence X-ray reflectivity pattern in a defect-free multilayer. The approximation is valid in the low-reflectivity theta ranges. For k = (4 pi sin theta)/lambda > 0.28 Angstrom(-1) (theta > 2 degrees wit h Cu K alpha radiation), the formula deviates by at most 1% from the r igorous matricial approach in the case of most metallic multilayers. T he main advantage of the approximation is that it allows the identific ation of features in the reflectance pattern, from which desired struc tural parameters (average layer thicknesses, external and internal rou ghness) can be estimated easily. This approach yields average structur al parameters, best approximating those of a real multilayer but ignor ing possible defects.