Baptiste Girault

Copper coverage effect on tungsten crystallites texture development in W/Cu nanocomposite thin films

Morphological and crystallographic structures of multilayered W/Cu nanocomposite thin films elaborated by physical vapor deposition were studied by varying copper and tungsten thicknesses. Sample examinations were performed by x-ray diffraction (XRD), grazing incidence small-angle x-ray scattering and transmission electron microscopy (TEM). Samples were found to be composed of copper nanoparticles, homogeneously dispersed in planes parallel to the film-substrate interface and periodically separated by tungsten layers along the growth direction. Our observations revealed an original texture development of the tungsten matrix from a mixture of unexpected α-W⟨111⟩ and α-W⟨110⟩ components to unique α-W⟨110⟩ component as the copper coverage passes a thickness threshold of 0.6 nm. Local TEM texture stereology investigations revealed simultaneous columnar growth of both preferential orientations posterior to polycrystalline development while XRD reveals strong compressive residual stresses in both texture compon...

Size effects on the Mechanical Behavior of Nanometric W/Cu Multilayers

The mechanical behavior of nanostructured stratified W/Cu composites prepared by ion beam sputtering has been investigated using a method combining X-ray diffraction and tensile testing. Tests were performed on a synchrotron light source to analyze the elastic response of the tungsten phase. Three different microstructures have been analyzed: the specimen composed of the thinner tungsten layers reveals an elastic behavior different from the one expected assuming bulk elastic constants. However, Transmission Electron Microscopy (TEM) and Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) measurements reveal discontinuities in the copper layers. As the strain in the related copper clusters as well grains boundary contributions are not experimentally accessible, atomistic calculation are of utmost importance. Polycrystalline materials have already been constructed through the Voronoi method and thanks to TEM observations. Atomistic simulation and calculation are underway to validation.

Strains, stresses and elastic properties in polycrystalline metallic thin films: in situ deformation combined with x-ray diffraction and simulation experiments

X-ray diffraction is used in combination with tensile testing for measuring elastic properties of metallic thin films. Size effect, elastic anisotropy and grain morphologies are considered in all these experiments and supported by different kind of numerical simulations operating at different length scales. Such instrumental studies are time consuming even if synchrotron sources are used. New experiments are under progress for reducing acquisition data and improving precision on strain measurements. After introducing briefly the main principles and results of our techniques, first promising measurements on nanometric W/Cu multilayers using 2D CCD detectors and high monochromatic flux at the Advanced Light Source Berkeley (USA) on beam line 11.3.1 are presented. In addition, simulation experiments for analyzing elasticity in textured gold film are discussed.

Development of a biaxial tensile module at synchrotron beamline for the study of mechanical properties of nanostructured films

We have developed on the DIFFABS-SOLEIL beamline a biaxial tensile machine with synchrotron standard for in-situ diffraction characterization of thin polycrystalline metallic film mechanical response. The machine has been designed to test cruciform substrates coated by the studied film under controlled applied strain field. Technological challenges comprise the fixation of the substrate, the generation of a uniform strain field in the studied (central) volume, the operations from the beamline pilot. Tests on W and W/Cu multilayers films deposited on polyimide substrates are presented.

D-78 Elastic Properties of Nano-Structured Thin Films: Characterization and Modeling

different microstructures are elaborated, the microstructure of which being characterized by TEM (grain shape, layer thickness …), X-ray reflectometry (multilayer period, density) and X-ray diffraction (XRD: crystallographic texture, layer thicknesses). These films are supported by a polyimide foil substrate. Films mechanical response is characterized experimentally by XRD based in-situ techniques [2] to assess the orientation and depth dependences of elastic strain and stress. Results are interpreted by an appropriated mechanical modeling accounting for the material microstructure, based on homogenization schemes. An in-situ biaxial tensile apparatus is currently developed in the frame work of the French Agency for Research (Cmonano project, ANR-05-PNANO-069) and will be installed at Diffabs beam line of the new French synchrotron SOLEIL. This machine allows exploring many different configurations of

ELASTIC PROPERTIES OF METALLIC THIN FILMS: 2D SYNCHROTRON XRD ANALYSIS DURING IN SITU TENSILE TESTING

Elastic behavior of thin films studied from in situ loading of the specimen during X-ray diffraction on a synchrotron source is presented. Model nanometric multilayer W/Au systems exhibiting different microstructures were analyzed. These films are supported by a (thin) polyimide substrate. X-ray diffraction in transmission geometry was used to study the deformations of both phases as a function of applied load. This geometry was developed with the aim of optimizing experiment time. Using 2D detectors and dynamical loading, measuring time is reduced considerably, down to a few hours compared to a one-week experiment in a laboratory. Furthermore, the in-plane strain state is measured in all directions with great

X-ray Diffraction Study of the Mechanical Elastic Properties of Nanometric W/Cu Multilayers

The mechanical behavior of W/Cu multilayers with a period of 24 nm and a 1/3 W/Cu thickness ratio prepared by magnetron sputtering was analyzed using a method combining X-ray diffraction and tensile testing. Tests were performed both with a conventional and a synchrotron light source to analyze the elastic response of the system. Comparison between the strain-load curves obtained in both experimental conditions and estimated curves clearly shows that high quality synchrotron measurements are a preliminary condition for size-effect studies. Moreover, cyclic tests were used to determine the elastic domain of each material and compare their mechanical responses. Plastic strain was observed in copper before in tungsten layers in accordance with the mechanical behavior of their bulk counterparts.