Diffuse contribution to specular spectra and the specular contribution to diffuse spectra in X-ray scattering from rough interfaces

The angular dependences of the intensity of X-ray radiation scattered from multilayer systems with nonideal interfaces are investigated with due regard for the real geometry of a receiver. The influence of the interface roughness and the longitudinal and transverse correlations of the interface roughnesses on the specular- and diffuse-scattering spectra is analyzed. It is demonstrated that the inclusion of the diffuse contribution to the specular-scattering spectra provides information on the correlation lengths in the plane and in the direction perpendicular to the plane of the interface. The roughness parameters determine the ratio between the heights of the central Bragg peak and the diffuse plateau in the diffuse-scattering spectra. The spectra measured for several widths of the detector slit make it possible to separate the true specular and diffuse contributions. This allows one to interpret experimental data more accurately. The results of the calculations are illustrated by analyzing experimental scattering spectra for multilayer systems.