Restoration of structure of thin multilayer films from reflectivity data by stepwise model refinement

The computational experiment on the restoration of the model parameters of the cross-section profile of the scattering density of thin multilayer films is described. It is shown that the use of the stepwise model of the structure, which is described by the thickness, density, absorption, and roughness parameters makes the problem of profile restoration multimodal and ill-conditioned. The analysis of the numerical experiments performed allowed us to propose a procedure of consecutive refinement of the initial-model parameters using the results of the local minimization of the discrepancy functional applied for the characteristic segments of the reflectivity curve. The methods proposed were used to restore the structure of a multilayer film deposited on a silicon substrate by the Langmuir-Blodgett method.