X-ray scattering from nonideal multilayer structures: Calculations in the kinematical approximation

In the kinematical approximation, a two-dimensional model is described for X-ray scattering from multilayered films that includes discrete thickness fluctuations and interfacial correlated roughness. In this work, the influence of the thickness fluctuations and of the roughness that is introduced as small perturbations at the interfaces is studied on both specular and nonspecular reflectances. For specular direction, the kinematical calculations are compared with those calculated using the full optical Fresnel theory. It is shown that whenever the reflectance is low, both computations are in good agreement. Finally, the model is applied tentatively to fit the experimental specular and nonspecular spectra performed on Fe/Si multilayered samples.