The distribution of the contrast of X-ray standing waves fields in different media

X-ray standing waves (XSW) fields generated by total external reflection at different types of interfaces have been analyzed in order to determine the vertical distribution of interference contrast. The intensity contrast between the nodes and antinodes of the XSW field is of high relevance for the interpretation of fluorescence curves. Silicon wafers covered by nanoparticles, polymer layers and a liquid film containing ions were irradiated by XSW fields of 10 to 15.5 keV. From the deviation of the experimental data from the signals simulated assuming a field of constant contrast, the relation between the node/antinode contrast and the distance from the reflecting substrate was determined. For the interface solid/air, a decrease of contrast was measured; for solid/medium interfaces, a complete fading of the interference within the measurement range was observed. - Highlights: ► Finite coherence and scattering processes limit the contrast of XSW fields. ► Contrast distribution is determined by a modification of the simulation procedure. ► In scattering media, the XSW field fades within 30 to 180 nm. ► Improved estimation of element distribution profiles by knowledge of contrast function.