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The thermal stability of Cu/W nano-multilayers deposited on a Si substrate using ion beam deposition was analyzed in situ by GISAXS and transmission EDX—a combination of methods permitting the observation of diffusion processes within buried layers. Further supporting techniques such as XRR, TEM, WAXS, and AFM were employed to develop an extensive microstructural understanding of the multilayer before and during heating. It was found that the pronounced in-plane compressive residual stress and defect population induced by ion beam deposition result in low thermal stability driven by thermally activated self-interstitial and vacancy diffusion, ultimately leading to complete degradation of the layered structure at moderate temperatures. The formation of Cu protrusions was observed, and a model was formulated for stress-assisted Cu diffusion driven by Coble creep along W grain boundaries, along with the interaction with Si substrate, which showed excellent agreement with the observed experimental data. The model provided the explanation for the experimentally observed strong correlation between thin film deposition conditions, microstructural properties, and low thermal stability that can be applied to other multilayer systems.

Surface treatments of Ti-6Al-4V alloys are of utmost importance for biomedical applications since they allow for tribological gain. Here, Ti-6Al-4V disks have been PBII nitrided at either 500, 600, 700 and 800 °C. A set of techniques (XRD, SEM-EDS, EBSD and GDOES) was used to characterize the surface microstructural and chemical changes. Nanoindentation was used to assess the induced changes in terms of mechanical properties. Two types of nitrided domains are revealed. Starting from the surface, a nitride bilayer composed of δ-TiN/ϵ-Ti2N with enhanced surface resistance is supported by an α-Ti(N) solid solution formed at depth. Hardness values peak at 12–14 GPa at the surface, which is almost twice as large as the bulk value (about 7 GPa). For the moderate temperatures used here, a deep (10–15 µm) and strong hardness (14 GPa) enhancement together with a smooth gradient can be achieved.

International audience; This topical review covers the mechanical properties of natural fiber composites (NFCs) that allow applications in many application fields ranging from infrastructure to transportation. Climate change alerts on the importance of sustainability and NFCs offer opportunities when compared to conventional glass-fiber composites. Advantages and drawbacks of NFC versus synthetic composites are considered and discussed. Mechanical properties are assessed both statically and dynamically. The hydrophilicity and its consequences on damage and deformation mechanisms are also addressed. The key to making well-reinforced composites is by ensuring that there is a strong interface between the reinforcing phase and the matrix phase. The interfacial bonding quality is thus discussed through various testing methods and the effects of surface treatments are presented.

International audience

En 1989, l’historienne Catherine Gousseff s’est rendue a Vilnius dans le cadre de l’enquete collective « Memoire grise a l’Est » initiee par la BDIC. Dans cet entretien, elle revient sur les conditions de realisation de cette recherche et les questionnements qui l’animaient alors sur les memoires des communautes culturelles de la ville.

Le pacte germano-sovietique et ses clauses secretes font l’objet, depuis la signature du 23 aout 1939 de controverses, de relectures successives et d’interpretations divergentes. Si les consequences du pacte sur la Pologne et l’entree en guerre d’une partie de l’Europe sont bien identifiees, son importance pour le devenir des pays baltiques est parfois plus meconnue. Ce numero s’efforce a l’aide des sources de La contemporaine et d’ailleurs de donner un apercu des recherches les plus recentes en la matiere.

When thin metallic multilayers deposited on a compliant polymer substrate are subjected to stretching, a “brick wall” fracture pattern arises that is associated with a non-uniform two-dimensional stress-strain state evolving as a function of the underlying substrate stretch. The present study is devoted to in situ mechanical microscopy of strain states in a copper/tungsten 18/6 nm multilayer using the combination of synchrotron Scanning X-Ray Diffraction Microscopy (SXDM) and Scanning Electron Microscopy (SEM), coupled with Digital Image Correlation (DIC). We demonstrate that these methods allow spatial variation of the coating strain to be mapped and compared with theoretical predictions based on shear lag theory, allowing the fracture properties of the multilayer to be extracted.

A novel experimental approach to study the cyclic plastic deformation of thin metallic films is presented. 300 nm thick Ni films are deposited on both sides of a pre-tensile soft substrate which allows to deform the films alternately in tension and compression (approximately from +2.7 GPa down to −2 GPa) relative to the as-deposited residual stress state. Nanocrystalline thin films' intrinsic elastic strains (or stresses) and true strains have been measured step by step during two loading/unloading cycles thanks to the X-ray diffraction (XRD) and digital image correlation (DIC) techniques respectively. From the first cyclic deformation, a significant Bauschinger effect is evidenced in the films, however, little or no cyclic hardening is observed during the two cyclic tests.

Instrumented Indentation Testing is applied on a fluoroelastomer so as to get information about the local mechanical response of such a rubbery material. Due to their viscoelasticity, elastomers exhibit a time-dependence, responsible for a variation in their behavior as a function of the stress or strain rate. A few studies highlight modifications of the indentation hardness H and modulus E r when the load function varies. However, these works concern polymers and, to our knowledge, such an investigation has not yet been carried out on elastomeric materials. Results about the influence of the loading-unloading procedure on E r are presented here. They show elastic modulus' variations depending on the chosen protocol's time scale and reported evolutions are consistent with the expected behavior of viscoelastic materials. Furthermore, in preparation of this main study, preliminary verifications were necessary since sources of error are known to distort indentation results. A focus on the microstructure and roughness is presented in this paper and reveals, in particular, a non-negligible improvement of indentation curves (load-displacement hystereses) with an appropriate sample preparation and surface finish. These results have finally been used as a basis for the study of local gradients within a rubber sample. This study revealed a gradient (i.e. an increasing modulus) from the outer part of the sample to the inner one, attributed to thermal effects during the molding.

Residual stresses in thin films and multi-layered coatings fabricated by physical vapour deposition largely affect their mechanical and thermal reliability during operation in numerous fields of applications. By changing the argon working pressure in between each multilayer planar DC magnetron sputter deposition step, it is possible to control the residual stress distribution within coatings. A combination of FIB-DIC ring-core strain analysis, synchrotron XRD analysis based on the sin2(Ψ) method and micro-cantilever deflection analysis is used to reconstruct the in-plane stress state of multilayer coatings at different deposition pressures, with a residual stress depth profile resolution of 50 nm. A clear transition from compressive to tensile residual stresses is observed with an increase of working pressure, with pronounced stress peaks near the substrate-coating interface. These peak stresses resolved by FIB-DIC ring-core analysis exceed the average XRD stress measurements significantly, thus providing a reasonable explanation for multilayer failure. Experimental results are presented and comprehensively discussed in the context of deposition conditions for different thin film applications.

International audience; L’article introductif analyse les collections sur les pays baltiques / républiques socialistes soviétiques baltes / États baltes de la contemporaine. La région balte est difficilement identifiable dans les collections, du fait de son destin heurté au Vingtième siècle ou du peu d’intérêt qu’on lui porte. Seuls deux grands ensembles documentaires sont abondamment alimentés : l’un concerne les minorités germanophones de la région, l’autre la « question balte » pendant la guerre froide. Cette situation s’explique par des logiques d’acquisition et des enjeux internationaux bien spécifiques.

International audience

In this paper, a method is proposed to determine the in-plane elastic modulus of thin films. Thanks to our custom-designed dual digital image correlation (DIC) system, it is possible to measure the time-resolved strain of film and substrate simultaneously during the microtensile testing. The macroscopic strain difference between coated and uncoated section allows extracting the elastic constants of thin films with high precision. In the case of 400 nm tungsten films coated on each side of one substrate over half of the gauge length, the value obtained agrees well with the bulk one. Furthermore, finite element method (FEM) has been performed to simulate the mechanical behavior of the specimen. High consistency with theoretical and experimental results is verified.

Soft chemistry (chimiedouce) processes allow the design of multifunctional composite coatings tailoring the interfaces between phases. Instrumented indentation has become routinely used to characterize thin systems and allows for getting insight into interface mechanics. The paper illustrates both experimental approaches allowing for the fabrication PMMA based nanocomposites and their characterization employing nanoindentation.

Direct bonding of III-V semiconductors on silicon has recently become a promising technology for the fabrication of hybrid photonic integrated circuits (PICs). In such hybrid PICs, active optical functions (amplification, emission) are ensured by the direct-gap III-V semiconductor and passive functions (guiding, switching) by the Si guiding layer. One particularly attractive feature of hybrid III-V/Si platforms is the possibility to densely integrate a variety of advanced optical functions in the guiding layer using sub-100 nm patterns in the silicon. Nano-patterning the silicon surface may, however, weaken the adhesion of the III-V semiconductor to silicon, potentially making the hybrid bonded stack subject to debonding in subsequent processing steps, such as cleaving. In this context, quantitatively assessing the adhesion of the III-V to Si in a patterned area and comparing it against the adhesion in a nearby unpatterned area can provide one with feedback useful for improving the patterning , post-patterning surface preparation, or bonding processes. Ultimately, such measurements can allow one to propose optimal designs for advanced embedded optical functions in hybrid III-V/Si PICs. Instrumented nanoindentation, Atomic Force Microscopy and Scanning Transmission Electron Microscopy have been combined ex situ to study the adhesion of thin InP membranes to bulk (100) silicon substrates but also to sub-100nm patterned (100) silicon substrates. Three distinct regimes are identified in the deformation of the InP/Si stacks during these experiments: the first is plastic flow of InP at low loads; the second is elastic debonding of the InP membrane, far from the indented zone at medium loads; lastly, the local amorphisation of the underlying Si substrate at high loads. The regime of intermediate loads is shown to be particularly useful in the evaluation of the surface bonding energy of InP to Si [1,2]. [1] K. Pantzas, E. Le Bourhis, G. Patriarche, A. Itawi, G. Beaudoin, I. Sagnes and A. Talneau Eur. Phys. J. Appl. Phys. 65 (2014) 20702 [2] K. Pantzas, E. Le Bourhis, G. Patriarche, D. Troadec, G. Beaudoin, A. Itawi, I. Sagnes and A. Talneau Nanotechnology 27 (2016) 115707

A partir de l’extrait declassifie d’un decret du Conseil des ministres de l’URSS, l’article examine la politique sovietique de deconcentration urbaine engagee en 1956 en tant que politique de la ville et preparation a la guerre froide. Au travers d’echanges portant sur la preparation et la mise en œuvre du decret, il restitue le jeu de specialistes de la ville, non-militaires, pour examiner le profit qu’ils tirent a la fois de la menace atomique et du renforcement du secret d’Etat, et la convergence entre objectifs de defense et de transformation des villes.

InP membranes have been bonded oxide mediated onto a patterned and unpatterned Si substrate. Indentation is shown to allow local testing on patterned areas. Both responses on patterned and unpatterned are compared and placed in reference to oxide free bonded membranes. Delamination of the membrane was observed to depend on the presence of patterns in the Silicon substrate. It occurs when the indenting load reached 55 mN for an oxide mediated bonded unpatterned structure and 42 mN for an oxide mediated bonded patterned one. This is in both cases below the value of 80 mN obtained for an oxide free bonded membrane (unpatterned). Weibull analysis of these events yielded a modulus m of magnitude 6 to 10, indicating that delamination fracture is relatively predictable with a weaker resistance obtained in patterned oxide mediated bonding. Delamination of the membrane is the result of constraint of plastic flow by the InP/Si interface. Membrane rotation is induced and increases with the indentation load, until it is sufficient to initiate and propagate an interfacial crack.

Nanostructured metallic multilayers with carefully designed mechanical and functional properties are omnipresent in cutting edge technological applications. To ensure the mechanical integrity of such coatings, the Mode I critical Stress Intensity Factor KIC is used to quantify their fracture toughness in order to avoid material failure by appropriate design. In this article, we present a novel approach for the KIC determination of thin and ultrathin films on compliant substrate, based on micro-displacement field analysis using Digital Image Correlation within SEM. Using this method, KIC of a Cu/W nano-multilayer with a total coating thickness of 240 nm was determined as K IC = 4.8 ± 0.05 MPa m , showing excellent agreement with the values published for comparable systems in the literature. To verify the validity of the chosen approach, two independent finite element simulations were employed, thus revealing the role and effect of the compliant substrate on the stress and displacement fields arising around the crack tip in thin films.

Les premieres sources visuelles relatives a la region balteconservees a La contemporaine datent de la Premiere Guerre mondiale dont les combats se sont prolonges jusqu’en 1920 dans la region. Elles sont essentiellement le produit de points de vue allemands sur la region. A ce titre, elles refletent tres bien differents imaginaires allemands qui seront encore tres vivaces lors de la signature du pacte germano-sovietique en 1939.

International audience

Hypothesis The poor miscibility of carbon nanotubes (CNTs) in common organic solvents and organic monomers requires their modification by suitable functional (reactive or not) groups prior to their incorporation in thermoplastic polymers. Experiments Dispersion behavior of carbon nanotubes and mechanical properties of various CNT–poly(methylmethacrylate) (PMMA) nanocomposites were investigated. We studied the influence of the surface chemistry through the use of diazonium salts as an elegant and environmentally friendly platform to provide a suitable sidewall functionalization by methyl methacrylate functions. We used either a molecular size functional group through the grafting of methacryloxypropyltrimethoxysilane or a macromolecular size one, consisting in PMMA brushes grown by SI-ATRP in order to study the influence of the length of methacrylate function on the dispersion of CNT in PMMA. Findings The hardness and the elastic indentation modulus of all hybrid films were obtained through nanoindentation measurements and found to increase, using ATRP-modified CNTs, suggesting a better dispersion of CNTs in PMMA due to optimal inorganic–organic interactions promoted by the short chains of PMMA.

Synchrotron X-ray diffraction is a powerful tool to analyse the mechanical behavior of multiphase materials due to its selectivity. Simultaneous stress analysis of both phases of a W/Cu thin multilayer has been performed during a continuous biaxial loading on DiffAbs beamline at SOLEIL synchrotron (France). The use of a 2D detector with a large sample-detector distance is shown to give relatively accurate applied stress analysis even if only a small part of the usual ψ range of the sin2ψ method is considered. The results show the failure of the thin film multilayer while the W components are still under a strong compressive stress state of-3 GPa. It is concluded that the mechanical behavior is in fact mainly governed by the residual stress state.

We report on the mechanical response of semiconductor substructures formed by InP membranes bonded to silicon. The bonded surfaces are of the order of ~ 1 cm2 and were bonded using oxide-free direct wafer bonding. Both the plastic response of the InP membrane and the InP/Si interface strength have been investigated using instrumented nanoindentation.

International audience; No abstract available

In situ biaxial tensile tests were carried out on W/Cu nanocomposite thin films deposited on a polyimide cruciform substrate. A biaxial testing machine developed on the DiffAbs beamline at the French SOLEIL synchrotron allows for scrutinizing the mechanical behaviour of crystalline thin films at the micro-scale and the macro-scale using simultaneously synchrotron X-ray diffraction and digital image correlation techniques. Both strain analyses have been performed for two controlled non-equibiaxial loading paths: loading ratios of 0.8 and 0.33. The mechanical response is analysed and compared for the two loading ratios.

Nanocrystalline metallic coatings of sub-micron thickness are widely used in modern microelectronic applications. In X-ray diffraction experiments to determine both the residual and applied stresses in nanocrystalline coatings, one difficult challenge that comes up invariably is the determination of the strain-free lattice spacing d. The present study addresses this challenge by using the focused ion beam (FIB) to generate a built-in strain-free reference by patterning (milling) a 50 × 50 μm region of the coating to produce an array of small stress-relieved "islands" ~ 0.8 × 0.8 μm each. Transmission X-ray diffraction setup was used for data collection at DIFFABS beamline (Synchrotron SOLEIL, France). A 150 nm-thick multi-layered W-Cu nano-composite thin film on polyimide (Kapton®) substrate was studied. The samples were loaded incrementally using a compact uniaxial loading device, and micro-beam diffraction data were collected on and away from the reference array. It was shown experimentally that the "island" array remained approximately strain free throughout the experiment, providing an on-board d lattice spacing reference. The changing lattice spacing d in the coating was also monitored away from the array, to deduce the elastic strain evolution during deformation. The results and their implications are presented and discussed. © 2013 Elsevier B.V. All rights reserved.

To get further insight into Nitrogen stoichiometry influence which is of utmost importance since it influences the phase structure and consequently the mechanical properties of the AlCrN coatings, we carried out a systematically study of AlCrN coatings comprising coatings production, mechanical properties survey, and composition and phase structure characterizations. Al1-xCrxNythin films have been synthesized by two physical vapour deposition - PVD systems: ion- beam (IBS) and magnetron sputtering (MS). Composition of the coatings was studied by both Energy Dispersive X- ray Spectrometer (EDXS) and Rutherford Backscattering Spectroscopy (RBS), the latter technique being very sensitive to light elements such as nitrogen. Most compositions are revealed to be sub- stoichiometric with Nitrogen (y 1-xCrxNyfilms show a similar coefficients of friction (COF) evolution with average values observed between 0.4 – 0.8 depending on the nitrogen content.

The trapping of nanoparticles inside a hybrid matrix is of great importance for the design of flexible devices with good mechanical properties and for the manipulation of nanoparticles whilst avoiding the use of nanopowders. In this work, transparent coloured coatings on glass were prepared by incorporating Goethite nanorods in a silica:PHEMA [poly(hydroxyethyl methacrylate)] hybrid matrix. Results show that incorporation of Goethite with a volume content higher than 27 % leads to the formation of a porous structure through a phase separation mechanism which induces a dramatic collapse of the mechanical properties. When the Goethite volume content is below 16 %, the mechanical properties of the coating are governed by the interactions between organic and inorganic domains. Goethite interacts preferentially with the silica network through the formation of hydrogen bonds and no direct interactions with PHEMA were observed. In the absence of strong covalent bonds between the silica:PHEMA hybrid and the nanoparticles, Goethite nanorods do not provide any mechanical strengthening. As a result, interpenetration between silica and PHEMA networks enables fine tuning of the final mechanical properties with the coating silica content.

The (001) GaAs surfaces have been modified by thin elastically stressed InGaAs-buried layers and tested under Berkovich contact. The elastic–plastic transition determined from the pop-in event observed in the force control mode of the indentation machine appears at slightly lower loads (0.44–0.46 mN) when compared to bare GaAs surface (0.50 mN). Estimations indicate that for both studied sublayers, the stored elastic energy is about 20% of the elastic indentation energy reached at elastic–plastic transition when the sublayer is observed not to relax plastically.

In situbiaxial tensile tests within the elastic domain were conducted with W/Cu nanocomposite thin films deposited on a polyimide cruciform substrate using a biaxial testing machine developed on the DiffAbs beamline at the Synchrotron SOLEIL. The mechanical behaviour of the nanocomposite was characterized at the micro- and macroscales using synchrotron X-ray diffraction and digital image-correlation techniques simultaneously. Strain analyses for equibiaxial and non-equibiaxial loading paths were carried out. The results show that the two strain measurements match to within 1 × 10−4in the elastic domain for strain levels less than 0.3% and for both loading paths.

Instrumented indentation mechanics and its applications to ceramics characterisation are described and discussed. Instrumented nanoindentation has become an outstanding tool for characterising surfaces and is routinely used in industry and university. The article reviews important procedures and concepts that have proved to be very useful to analyse the contact response of ceramics (elastic–plastic loading, indentation strains and stresses, crack generation, composite response of coated pieces). Examples are used to illustrate the very wide range of studies that can be carried out.

A magnetron sputtering system was used to deposit AlCrN thin films. Chemical compositions of the films were determined by both EDXS and RBS, while structures analyses were conducted by XRD in a Seifert XRD3000 diffractometer. Macroscopic residual stresses of films were determined by curvature measurements using DEKTAK IIA profilometer, while in-grain stresses were extracted by the “sin²Y method” from XRD measurements. A nanoindenter from CSM (Switzerland) was used to determine the hardness of the films. A CrN type FCC structure was obtained with a strong (200) fiber texture for the range of compositions Al1-xCrxNy(0.56 < x< 0.89) of interest here. The global stresses were compressive for all FCC films resulting from the high energetic deposition conditions used. In-grain compressive stresses were determined for the films with thickness < 500nm, while thicker films (> 500nm) showed tensile in-grain stresses. Stress-free lattice parameter a0strongly decreased from 4.13 to 3.97 A°. Hardness values were obtained in a range extending from 17 to 27 GPa with an increase obtained as Cr content increases and correlated to the residual-stress level.