Mesoscale x-ray diffraction measurement of stress relaxation associated with buckling in compressed thin films

Compressed thin films deposited on substrates may buckle depending on the geometrical and mechanical properties of the film/substrate set. Until recently, the small dimensions of the buckling have prevented measurements of their local in plane internal stress distribution. Using a scanning x-ray microdiffraction technique developed at a third generation x-ray synchrotron source, we obtained thin film internal stress maps for circular blisters and telephone chord buckling with micrometric spatial resolution. A fair agreement was found between the film delamination topology observed by optical microscopy and the measured stress maps. We evidenced residual stress relaxation associated with the film buckling: the top is essentially stress free while adherent region exhibits large compressive stresses.