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

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Nanostructured tungsten thin films have been obtained by ion beam sputtering technique stopping periodically the growing. The total thickness was maintained constant while nanostructure control was obtained using different stopping periods in order to induce film stratification. The effect of tungsten sublayers' thicknesses on film composition, residual stresses, and crystalline texture evolution has been established. Our study reveals that tungsten crystallizes in both stable aand metastable b-phases and that volume proportions evolve with deposited sublayers' thicknesses. a-W phase shows original fiber texture development with two major preferential crystallographic orientations, namely, a-Wh110i and unexpectedly a-Wh111i texture components. The partial pressure of oxygen and presence of carbon have been identified as critical parameters for the growth of metastable b-W phase. Moreover, the texture development of a-W phase with two texture components is shown to be the result of a competition between crystallographic planes energy minimization and crystallographic orientation channeling effect maximization. Controlled grain size can be achieved for the a-W phase structure over 3 nm stratification step. Below, the b-W phase structure becomes predominant. V C 2013 AIP Publishing LLC. [http://dx.

Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Controlled nanostructuration of polycrystalline tungsten thin films

Girault

Eyidi

Goudeau

et al. 2013

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“…The unique a-W h110i texture component is obtained from a thickness threshold of Cu determined at 0.6 nm. 31 Energy-dispersive X-ray spectroscopy was used in a scanning electron microscope in order to determine the atomic concentrations of Cu and W in the film. The volume fraction of the Cu phase has been estimated to be about 20% of the global thin film volume.…”

Section: W/cu Nanocomposite Based On Copper Disperso€ ıDs Thin Filmsmentioning

confidence: 99%

Comparative study of the mechanical properties of nanostructured thin films on stretchable substrates

Djaziri

Renault

Bourhis

et al. 2014

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International audienceComparative studies of the mechanical behavior between copper, tungsten, and W/Cu nanocomposite based on copper dispersoid thin films were performed under in-situ controlled tensile equi-biaxial loadings using both synchrotron X-ray diffraction and digital image correlation techniques. The films first deform elastically with the lattice strain equal to the true strain given by digital image correlation measurements. The Cu single thin film intrinsic elastic limit of 0.27% is determined below the apparent elastic limit of W and W/Cu nanocomposite thin films, 0.30% and 0.49%, respectively. This difference is found to be driven by the existence of as-deposited residual stresses. Above the elastic limit on the lattice strain-true strain curves, we discriminate two different behaviors presumably footprints of plasticity and fracture. The Cu thin film shows a large transition domain (0.60% true strain range) to a plateau with a smooth evolution of the curve which is associated to peak broadening. In contrast, W and W/Cu nanocomposite thin films show a less smooth and reduced transition domain (0.30% true strain range) to a plateau with no peak broadening. These observations indicate that copper thin film shows some ductility while tungsten/copper nanocomposites thin films are brittle. Fracture resistance of W/Cu nanocomposite thin film is improved thanks to the high compressive residual stress and the elimination of the metastable beta-W phase

“…11 Cu/W nano-composites and NMLs have received increasing interest in the last decade. [12][13][14] The high thermal conductivity of Cu and the low thermal expansion coefficient of W make Cu-W composites attractive for thermal management applications. The Cu-W system is highly immiscible due to the different crystal structures of Cu and W (fcc vs. bcc), their lattice parameter mismatch (15% difference), and their positive mixing enthalpy (þ36 kJ).…”

Section: Introductionmentioning

confidence: 99%

The effect of thermal treatment on the stress state and evolving microstructure of Cu/W nano-multilayers

Cancellieri

Moszner

Chiodi

et al. 2016

The functionality and reliability of nano-multilayered devices and components are largely affected by the stress evolution during fabrication, processing, and operation. The impact of thermal treatment on the stress state and evolving microstructure of Cu/W nano-multilayers, as deposited on different substrates (i.e., Si(001), Al 2 O 3-C, and Al 2 O 3-R) by magnetron sputtering, was investigated by in-situ high temperature X-ray diffraction and high-resolution scanning electron microcopy. The as-deposited Cu and W nanolayers exhibit an out-of-plane orientation relationship according to Cu h111ijj W h110i. On the Al 2 O 3-C and Al 2 O 3-R substrates, the Cu/W nanomultilayers also develop a pronounced in-plane texture given by Cu f111gh10 1ijj W f110gh00 1i. The stress state of the Cu nanolayers in the as-deposited state and upon heating, investigated ex-situ, is largely imposed by the accumulated stresses in the much stiffer W nanolayers. In the as-deposited state, the W nanolayers exhibit a much larger in-plane compressive stress than the Cu nanolayers (i.e., À3.5 GPa versus À1.5 GPa), which both mainly originate from growth stresses generated during the deposition process. The growth stresses in the as-deposited Cu nanolayers are relaxed after annealing at 500 C. Relief of compressive stresses in the W nanolayers is accompanied by grain coarsening which only occurs upon degradation of the nano-multilayered structure. The degradation of the periodic layer structure proceeds in the range of 750 À 900 C and is independent of the substrate.