Separation of the diffuse contribution to the specular x-ray scattering of multilayer films

X-ray reflectivity measurements from multilayer films contain information not only about the layer thickness and interface roughness but also about correlations of the interface roughness parallel and perpendicular to the interface. Due to the finite size of the receiving detector slit, it collects both purely specular and diffusely scattered radiation. Separation of the diffuse contribution to the spectra of specular reflectivity is an important task of processing the experimental data. For this purpose we suggest and implement a measurement method for specularly scattered scans integrated over several solid angles determined by the size of detector slits. Since in all cases the specular reflectivities coincide, this approach allows a separation of the diffuse and pure specular contributions. This separation is, in turn, required for obtaining information about the in-and out-of-plane structural correlation lengths. The method was used to analyze the experimental data of two multilayer systems with different interface properties: MgO/[V(1.212 nm)/Fe(0.715 nm)](25)/V(24.24 nm)/Pd(5-8 nm) and SiO2/Si/[CoFeB(2.55 nm)/MgO(1.8 nm)](15).