The investigation of [Fe/Cr] multilayer by GISAXS.

Grazing Incidence Small Angle X-ray Scattering (GISAXS) has been used for characterization of a cluster structure of the [Fe/Cr]30 multilayer with ultrathin iron layers. The experiment was performed at the “Langmuir” station of the Kurchatov Center of Synchrotron Radiation and Nanotechnology. Experimental GISAXS image has shown the side satellites and the Bragg peak revealing the existence of density inhomogeneities with an average lateral distance of ∼19 nm periodically repeated along depth. The modelling of the obtained image has been done in the DWBA approximation. It has been shown that for the wavelength used in the experiment (0.0951 nm) it is not possible to distinguish if the inhomogeneities exist in the Fe or in the Cr layers due to the small optical contrast between Fe and Cr layers. However, as it has been demonstrated by model calculations, in the case of the enhanced optical contrast (e.g. for the wavelength corresponding to the L3 edge of Fe) the x-ray standing waves allow ones to select the cases of inhomogeneities in the Fe or in the Cr layers: the simulated GISAXS patterns are rather different for these two cases.