Sin2ψ analysis in thin films using 2D detectors: Non-linearity due to set-up, stress state and microstructure

Two synchrotron set-ups have been used to carry out in situ strain measurements on systems constituted by Au films on polyimide substrates. These film/substrate composites have been submitted to either uniaxial or equibiaxial loadings. For the two configurations, an area detector (2D) was employed to extract the so-called ε–sin2ψ curves. These latter are shown to be affected by geometrical effect unless equibiaxial loading is employed. Moreover, non-linearity of these curves can occur, even in the case of equibiaxial loading, when the film is thin (120 nm). This last phenomenon is explained by surface anisotropy.

► Synchrotron X-ray strain analysis of thin gold films on polyimide substrate using area detectors.
► Classical sin2ψ analysis must be used with care when strains are measured with 2D detectors, depending on the stress state.
► Surface anisotropy is evidenced for the thinnest film.