X-ray diffraction from inhomogeneous thin films of nanometre thickness: modelling and experiment

Abstract

The diffraction of X-rays by a thin layer (of the order of a few nanometres) with a gradient in interplanar spacings is considered. It is shown that optical coherence over the film thickness leads to diffraction peak positions that no longer obey Bragg's law. Although a fitting of the diffracted intensity is indeed still possible, this has direct consequences on the applicability of more straightforward analysis methods, such as the sin2ψ method, which rely on diffraction peak positions. The intensity and peak position calculations are supported by a comparison with experimental data from a (001) Fe/GaAs thin (3 nm) epitaxic film.