X-ray residual stress analysis in thin films under grazing incidence – basic aspects and applications

Abstract

Residual stress fields in polycrystalline materials induced by mechanical surface processing or coating often are highly inhomogeneous with respect to depth z below the sample surface. This even applies for thin films, the thickness of which is usually much smaller than the penetration depth t of the X-rays. Therefore, X-ray residual stress analysis in thin films is advantageously performed under grazing diffraction conditions. To avoid erroneous averaging over the film thickness, both the radiation used and the methods applied to analyse the residual stress distributions have to be adapted carefully to the particular situation. In this paper some fundamental aspects concerning the meaning of the X-ray penetration depth for very thin films and the important role of refraction in the generalised non-symmetric case of grazing incidence diffraction are discussed and illustrated by practical examples from different fields in thin film diffraction analysis.