Strain inhomogeneity in copper islands probed by coherent X-ray diffraction

The strain field of individual epitaxial sub-micrometric copper islands is studied using coherent X-ray diffraction and finite element modelling. The strain inhomogeneity in each island is so large that the characteristic features of the island shape tend to disappear in the diffraction pattern, which is dominated by strain effects. The model confirms the tensile strain imposed to the island by the thermal mismatch occurring during the preparation of the samples. An evaluation of the residual strain is obtained by qualitatively fitting the diffraction data. ► Copper sub-micrometric islands are obtained by solid state dewetting on Tantalum. ► Highly inhomogeneous residual strain is evidenced by coherent X-ray diffraction. ► Modelling of the diffraction data explains the effect of inhomogeneous strain. ► Strain effects are dominants over shape effects in diffraction patterns in such cases.