Nano-structuration effect on the mechanical behavior of gold thin films studied by 2D synchrotron x-ray diffraction

- Synchrotron XRD associated with a 2D detector in order to analyze elastic strains of nano-structured metallic thin films.
- The elastic strain stored in metallic thin films decreases when the thickness of thin films decreases.
- In-situ digital Image correlation in order to analyse macroscopic strain of thin films.

Thin film technology is pervasive in microelectronics, and in optical, magnetic or micro-mechanical devices. The mechanical performance of such nanoscale structure is crucial for applications since it is related to device lifetime. Furthermore, the mechanical behavior of nanostructured materials is still not well known. In this work, nanostructured gold thin films with different thicknesses have been elaborated by sequenced ion beam sputtering to study size effect. The grain size is controlled by stopping the grain growth during the thin film growth. Using the biaxial tensile setup developed at the DiffAbs beamline of the French synchrotron facility SOLEIL, x-ray diffraction (XRD) measurements have been performed during controlled biaxial deformation tests on gold thin films deposited on Kapton substrate. Strain analysis of the gold thin films with different grain size and architecture has been achieved for a non equi biaxial loading with a force ratio of 0.8. XRD allows measuring the intra-granular strains using the so-called sin2ψ method while the macroscopic in-plane strains are measured simultaneously thanks to Digital Image Correlation. By analyzing the mechanical response of the different films, we conclude that gold thin films follow a plastic deformation mode whatever the grain size or thin film architecture.