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The operation speed of dynamic random access memory devices has been increasing with respect to the evolution of electronic devices. This in turn has induced a decrease in the allowed time for the operation. Therefore, the effective capacitance degradation in which the capacitance gradually decreases with increasing frequency of applied ac voltage is a severe concern for decreasing capacitance during fast operation, in addition to inducing reliability degradation. Hence, in this article, the origin of capacitance degradation depending on operation frequency, also called “frequency dependence” of the capacitance, was revealed. By performing dc and ac nonlinearity analyses, the effect of defects, especially oxygen vacancies, on the electrical properties of metal-insulator-metal (MIM) capacitors was investigated. Eventually, the mechanism of frequency dependence related to oxygen vacancy in the insulator of the MIM capacitor was identified.

Metal–Insulator–Metal (MIM) capacitors based on high-k oxides require stability with the applied electric field. However, experiment reveals a nonlinear behavior of capacitance with ac or dc bias. In this work, we measure capacitance–voltage nonlinearities for Au/10-nm HfO2/M (where M = TiN, Pt, W, and AlCu alloys). It is observed that ac capacitance is strongly dependent on the bottom electrode material. This dependency is discussed through the correlated barrier hopping (CBH) model. Accordingly, the ac nonlinearity is ascribed to the polarization of isolated defect pairs, which in turn increase as the maximum barrier height decreases. This induces higher nonlinearity as compared to the dc one. For the dc bias, oxygen affinity of active metal electrode may describe the origin of dc nonlinearities.

The present work highlights the crucial role of the interfacial compatibilization on the design of polylactic acid (PLA)/Magnesium (Mg) composites for bone regeneration applications. In this regard, an amphiphilic poly(ethylene oxide-b-L,L-lactide) diblock copolymer with predefined composition was synthesised and used as a new interface to provide physical interactions between the metallic filler and the biopolymer matrix. This strategy allowed (i) overcoming the PLA/Mg interfacial adhesion weakness and (ii) modulating the composite hydrophilicity, bioactivity and biological behaviour. First, a full study of the influence of the copolymer incorporation on the morphological, wettability, thermal, thermo-mechanical and mechanical properties of PLA/Mg was investigated. Subsequently, the bioactivity was assessed during an in vitro degradation in simulated body fluid (SBF). Finally, biological studies with stem cells were carried out. The results showed an increase of the interfacial adhesion by the formation of a new interphase between the hydrophobic PLA matrix and the hydrophilic Mg filler. This interface stabilization was confirmed by a decrease in the damping factor (tanδ) following the copolymer addition. The latter also proves the beneficial effect of the composite hydrophilicity by selective surface localization of the hydrophilic PEO leading to a significant increase in the protein adsorption. Furthermore, hydroxyapatite was formed in bulk after 8 weeks of immersion in the SBF, suggesting that the bioactivity will be noticeably improved by the addition of the diblock copolymer. This ceramic could react as a natural bonding junction between the designed implant and the fractured bone during osteoregeneration. On the other hand, a slight decrease of the composite mechanical performances was noted.

International audience; Because of their characteristics, including a d33 of 10–15 pC/N and high stability up to temperatures over 1000 °C, polar glass–ceramics containing fresnoite crystals can be regarded as highly effective materials for applications requiring piezoelectricity at high temperatures. In the present paper we investigate barium substitutions in an Sr-fresnoite (STS) glass–ceramic. Two aspects are studied: first, the effect of the substitution on the preferential orientation of the crystallization, and second, the ability of the glass–ceramics to generate and propagate surface acoustic waves (SAW) at high temperatures. XRD analyses show that a 10 at.% substitution of Ba allows us to keep a strong preferential orientation of the (00l) planes of the fresnoite crystals down to more than 1 mm below the surfaces. Higher substitution levels (25 and 50 at.%), induce a non-oriented volume crystallization mechanism that competes with the surface mechanism. SAW devices were fabricated from glass–ceramic substrates with 0, 10 and 25 at.% Ba substitutions. Temperature testing reveals the high stability of the frequency and delay for all of these devices. The glass–ceramic with a 10 at.% Ba substitution gives the strongest amplitude of the SAW signal. This is attributed to the high (00l) preferential orientation and the absence of disoriented volume crystallization.

International audience; The fabrication and integration of sub-millimeter magnetic materials into predefined circuits is of major importance for the realization of portable devices designed for telecommunications, automotive, biomedical, and space applications but remains highly challenging. We report here a versatile approach for the fabrication and direct integration of nanostructured magnetic materials of controlled shaped at specific locations onto silicon substrates. The magnetophoresis-assisted capillary assembly of magnetic nanoparticles, either spherical or anisotropic, leads to the fabrication of high-performance Co-based permanent magnets and Fe-based supercrystals. Integrated sub-millimeter magnets as well as millimeter self-standing magnets exhibiting magnetic properties competing with NdFeB-based composites were obtained through this cost- and time-efficient process. The proof-of-concept of electromagnetic actuation of a micro-electromechanical system cantilever by means of these supercrystals highlights their potentiality as efficient integrated magnetic materials within nomadic devices.

We recently presented the elaboration and functional properties of a new generation of hybrid membranes for PEMFC applications showing promising performances and durability. The strategy was to form, inside a commercial sPEEK membrane, via in situ sol–gel (SG) synthesis, a reactive SG phase able to reduce oxidative species generated during FC operation. In order to understand structure-properties interplay, we use a combination of direct space (AFM/3D FIB-SEM) and reciprocal space (SANS/WAXS) techniques to cover dimensional scales ranging from a hundred to few nanometers. AFM modulus images showed the SG phase distributed into spherical domains whose size increases with the SG uptake (ca. 100–200 nm range). Using contrast variation SANS, we observed that the sPEEK nanostructure is mostly unaffected by the insertion of the SG phase which presents a fractal-like multiscale structure. Additionally, the size of both the particles (aggregates/primary) is much too large to be sequestered in the ionic pathways of sPEEK. These findings indicate that the SG-NPs mainly grow within the amorphous interbundle domains. Noticeable rightward shift and widening of the ionomer peak are observed with the SG content, suggesting ion channel compression and greater heterogeneity of the ionic domain size. The SG phase develops in the interbundle regions with a limited impact on the water uptake but leading to a discontinuity of ionic conductivity. This Fourier and real spaces study clarifies the structure of the hybrid membranes and brings into the question the ideal distribution/localization of the SG phase to optimize the membrane's stabilization.

The electronic structure and optical properties of monoclinic HfO2 (m-HfO2) and HfO2:Al2O3 alloys, from the density functional theory (DFT), are investigated. The calculated lattice parameters and optical properties of m-HfO2 are consistent with the experimental data. Upon alloying with Al2O3 (more than 25%), we observe that the bandgap of Hf-aluminate (HfAlO) increases. Moreover, some doping states in the top and bottom valence bands are induced, which enhance the visible absorption of HfO2. From the impedance spectroscopy analysis, it is observed that 90% of the Al2O3 content in HfO2 induces a reduction of oxygen vacancies (and ac conductivity) as well as an increase in the dielectric constant as compared to pure HfO2. In addition, from the J–V and C–V variations, both current density and capacitance voltage nonlinearities are reduced. The conduction mechanisms of HfO2 and HfAlO dielectrics are systematically investigated. According to the J–E plots, parameters like the optical dielectric constant and the effective barrier height are extracted. Results are consistent with the DFT calculations and show that the Hf0.1Al0.9O device may constitute a potential candidate for metal–insulator–metal capacitor applications.

International audience; A piezoelectric glass-ceramic containing Sr2TiSi2O8 crystals is synthesized and used to develop a SAW device tested up to 950 degrees C. This device consists of an input IDT that generates the wave and an output IDT that converts it into a measurable electrical signal. The evolution of amplitude and frequency of the output signal is recorded. This study highlights that the glass-ceramic remains able to generate and propagate SAW up to 950 degrees C. The variations of the signal between room temperature and 950 degrees C are discussed with respect to the thermomechanical properties of the glass-ceramics. The softening of the residual glass above its Tg increases the signal's amplitude thanks to the relaxation of the stresses. At higher temperatures, the low residual glass viscosity causes the damping of the SAW. Below Tg, the variations of the signal are explained by the thermal expansion mismatch between the crystals and the glass, inducing tensile stresses and damages.

Resistance switching is studied in conductive bridge memory structures made from atomic layer deposited HfO2 and Ag active electrode. Inert electrode is varied by using different substrates (TiN, W, Pt). HfO2 crystallinity is modified by varying the deposition temperature (300/350 °C) and the film thickness (10/20 nm). Current–voltage characteristics, as well as current–time characteristics (to access to the switching kinetics), are studied according to the inert electrode nature and HfO2 structural properties. Results are discussed along resistance transition mechanisms which imply (i) the generation of oxygen vacancies by electronic injection at the inert electrode, (ii) Ag diffusion along oxygen vacancy paths, and (iii) the reduction of silver ions controlled by the inert electrode/HfO2 interface. Best characteristics, in terms of stability, are observed with Pt inert electrode and 10 nm films. Crystalline and amorphous films (10 nm) provide similar characteristics. In 10 nm films, TiN and W inert electrodes lead to variability in electrical properties (parasitic sets during reset, switching time dispersion). Such a variability is related to high electronic injection at the TiN/HfO2 and W/HfO2 interfaces which creates a high density of oxygen vacancy paths (Ag diffusion paths). In thicker and well-crystallized films (20 nm), progressive set is observed. This is ascribed to conduction along oxygen vacancy paths, which dominates over conduction along Ag conductive bridges.

International audience; In a European project called CUBISM, humidity sensors based on IDT (Inter Digital Transducer) technology are developed for the generation and detection of surface acoustic waves (SAW). These sensors are designed to operate at high temperature (500°C) for monitoring the drying of refractory concrete. Indeed, this humidity monitoring is important because a sudden evaporation of the water during the achievement of the structure could lead to high pressures in the pores implying consequently the destruction of the structure. Thus, the optimization of the concrete drying cycle must be combined with relevant in-situ physical measurements (humidity, pressure, temperature) and thermomechanical modelling. The real-time availability of this physical data via specific sensors integrated into the concrete is therefore a key to effective drying monitoring. Thus, for this project and its specific constraints, we have chosen the development of SAW humidity sensors because they are the most suitable to meet the specifications. In this study, the optimized parameters include the nature of the humidity-sensitive layer, the nature of the piezoelectric substrate, the architecture of the electrode array and finally the electronic measurement setup.; Dans le cadre d’un projet européen nommé CUBISM, des capteurs d’humidité basés sur la technologie IDT (Inter Digital Transducer) pour la génération et la détection des ondes acoustiques de surface ou SAW (Surface Acoustic Wave) sont développés. Ces capteurs sont destinés à fonctionner à haute température (500°C) pour le suivi du séchage du béton réfractaire. Ce suivi de l’humidité est en effet important car une évaporation brusque de l’eau lors de la mise en œuvre risque d’exercer de fortes pressions au niveau des pores et par conséquent peut conduire à l’explosion de la structure. Ainsi, l'optimisation du cycle de séchage du béton doit être associée à des mesures physiques in-situ pertinentes (humidité, pression, température) et à de la modélisation thermomécanique. La disponibilité en temps réel de ces données physiques via des capteurs spécifiques intégrés dans le béton, est donc une clef pour un monitoring efficace du séchage. Ainsi, pour ce projet et ses contraintes spécifiques, nous avons privilégié le développement de capteurs d’humidité SAW car ils sont les plus à même de répondre au cahier des charges. Dans cette étude, les paramètres optimisés sont notamment la nature de la couche sensible à l’humidité, la nature du substrat piézoélectrique, l’architecture du réseau d’électrodes et enfin la chaîne de mesure électronique

Textured kaolinite and halloysite-based materials were shaped by tape casting in order to promote the alignment of clay particles along the tape casting direction and to investigate the structure evolution of these phyllosilicates during the dehydroxylation process. The crystallinity indexes HI and R2 of the starting kaolins (KRG and KCS) were determined and appeared close to values found for the well-ordered reference kaolin KGa-1b. The halloysite clay exhibited trimodal grain size distribution and tended to be less textured than KRG and KCS according to the (002) pole figures performed on green tapes. The constant heating rate derived kinetic parameters matched the expected range. We followed the dehydroxylation of kaolinite and halloysite through in situ high-temperature X-ray diffraction measurements at the ESRF synchrotron radiation source on the D2AM beamline. The dehydroxylation of these kaolinite and halloysite occurred between 425 &deg, C and 675 &deg, C for KRG and KCS and from 500 &deg, C to 650 &deg, C for halloysite. In addition, the evolution of the basal distance of kaolinite regarding the heat treatment temperature confirmed that the dehydroxylation process occurred in three steps: delamination, dehydroxylation, and formation of metakaolinite. The calculated coefficient of thermal expansion (CTE) along the c axe values were close to 17 &times, 10&minus, 6 &deg, C&minus, 1 for kaolinite (KCS and KRG) and 14 &times, 1 for halloysite.

This paper presents a novel methodology to observe the leakage current origin in SiOC:H low-$\kappa$ intermetallic dielectric as well as a method to localise electrically the breakdown point in usual comb/serpentine/comb structures. Our results indicate that high leakage current is a consequence of a global moisture-induced SiOC:H dielectric modification and demonstrate that EMMI observations of such leakage current is possible. Besides, we have disclosed and validated a fast electrical breakdown localisation method fully compatible with automated test steps such as Parametric Test to track eventual weaknesses in reliability structures for instance.

International audience; Highly loaded lubricated contacts may present a friction plateau on which the friction force becomes independent from the sliding velocity. Although this phenomenon has been known for a long time, its physical origin remains poorly known. The present paper aims at giving further insight on the physical mechanisms triggering the friction plateau. The study specifically focuses on the influence of pressure on the physical state of the lubricant. An uncoupled experimental approach (rheology, tribology, spectrometry) has been conducted on a model lubricant. The lubricant behavior has been probed both at rest by Brillouin light scattering spectroscopy and dynamically under stationary conditions in a lubricated contact. The first experimental approach led to evidence a transition pressure associated with the lubricant glass transition, which has then been correlated to the lubricant macroscopic response in friction. We show that the onset of the plateau behavior occurs for Hertzian pressures close to the glass transition pressure, corresponding to a very small fraction of lubricant in a “nominal glassy state” within the contact.

International audience; In this work, barium titanate thick films are produced at low-temperature using a modified sol–gel/ceramic powder technology named the composite route. In this process, a commercial BaTiO3 powder, doped or not by Li2O as sintering aid, is mixed with a stabilized titanium (IV) isopropoxide/barium acetate sol to obtain a composite ink. Two sols, using different solvents and chelating agents, are tested. Characterization of the evolution of theses sols with an increase in temperature is realized by thermal analyses (TGA and DTA) and X-ray diffraction. The four type of inks obtained are screen-printed on metallized alumina substrates and sintered. Microstructures and electrical properties of the sintered composite films are compared to those processed from a conventional ink obtained by dispersing the barium titanate powder in an organic vehicle. Measurements of dielectric/piezoelectric properties highlight higher charge coefficients d33 for composite thick films (69 vs. 45 pC/N for conventional thick films at close thickness values) despite a lower relative permittivity (340 vs. 658) certainly due to the presence of a single domain BaTiO3 nano-crystallites.

This paper presents the fabrication of high-performance micro-magnets for the electromagnetic transduction of MEMS. The fabrication method relies on the use of nickel microstructures electroplated onto silicon substrates to control the capillary assembly of cobalt nanorods via magnetophoresis under an external magnetic field. The resulting sub-millimeter size permanent magnets with thicknesses of up to $150\ \mu \mathrm{m}$ produce a stray field of 30 mT at a distance of $100\ \mu \mathrm{m}$ . We demonstrate that this magnetic induction is sufficient to actuate a silicon microcantilever by means of the Lorentz force and that the MEMS resonance frequency can adequately be measured using integrated piezoresistances. This novel room-temperature synthesis approach is foreseen to facilitate the integration of high-performance magnets into MEMS.

In this work, we propose a novel integration in order to significantly reduce the High Resistance State vari-ability and to improve thermal stability in Oxide-based Resistive Random Access Memory (OxRRAM) devices. A novel device featuring a metallic liner, acting as a parallel resistance, is presented. To assess the effect of this solution, we compare the results with a standard OxRRAM cell structure. A very good stability of the resistive states, both in endurance and temperature, is highlighted and explained thanks to a conductive fila-ment based model., Comment: This paper is an accepted abstract to the conference SSDM that was held in Japan in september 2019

The dissimilarities of the composition, crystal structure, and corrosion resistance of ZnAl hydrotalcite (ZnAl-HT) conversion films grown “in situ” on electrogalvanized (EG) steel substrate were investigated for different Al3+/Zn2+ ratios at pH 12. The corrosion behavior of all conversion films in 0.1 M NaCl was compared through electrochemical techniques. The composition, morphology, structure, and thickness of conversion films with different Al3+/Zn2+ ratios were characterized by Fourier-transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), and electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), and X-ray diffraction (XRD). The polarization curves indicated that the ZnAl-HT films provided anodic inhibition for EG steel and the inhibition efficiency of the ZnAl-HT conversion films increases sharply with decreasing the Al3+/Zn2+ ratios from 5/1 to 5/3, while, for the 5/4 and 5/5 ratios, the corrosion resistance of ZnAl-HT conversion films showed a downward trend after two immersion hours. However, the corrosion behavior of HT conversion films with the Al3+/Zn2+ ratios from 5/3 to 5/5 remained stable for a longer immersion time. The protection performance of the ZnAl-HT films can be attributed to the barrier effects, ion-exchange competitive adsorption of chloride ions, and protective deposition of ZnO on the EG steel surface.

Hydrotalcites intercalated with sebacate (HT-SB) were prepared by a coprecipitation method. The synthesized powder was characterized using infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and zeta potential measurements. The inhibitor release from HT-SB in a chloride solution has been determined by total organic content (TOC) analysis. The inhibitive action of HT-SB on carbon steel was investigated and compared with hydrotalcites intercalated by benzoate (HT-BZ) and 2-benzothiazolythio-succinic acid (HT-BTSA) using electrochemical measurements and SEM/EDX analysis. The results showed that the zeta potential of modified hydrotalcites and the release of corrosion inhibitors from modified hydrotalcites depend on the chemical structure of inhibitors. The anodic polarization curves showed that the three modified hydrotalcites behave as anodic corrosion inhibitors with an efficiency, at a concentration of 3 g/L, of 94% for HT-SB, 81% for HT-BZ and 92% for HT-BTSA. These efficiencies are higher than those measured for the organic inhibitors in chloride solutions highlighting a synergistic effect due to the combination of the hydrotalcite structure and carboxylate inhibitors. The inhibition effect of modified hydrotalcite depends not only on the intercalated organic inhibitors but also on the capability of adsorption of the hydrotalcite structure on a steel surface. HT-SB was easily dispersed in an epoxy coating improving the barrier properties at concentrations lower than 5 wt.%. The best protection was obtained with 1.5 wt.% HT-SB.

International audience; We describe a process for transferring a 200 nm thick, 200 mm wide monocrystalline silicon (mono c-Si) thin film from a silicon-on-insulator onto a flexible polymer substrate. The result is a stretchable and flexible ultra-thin semiconductor film that can be subjected to tensile stress experiments. The process uses off-the-shelf 200 mm wafers and standard polymer temporary bonding techniques. The backside substrate and buried oxide are removed using grinding and wet etching processes. No cracks or wrinkles are observed on the film prior to the tensile stress experiments. The stretching of the flexible structure results in up to 1.5% uniaxial tensile elastic strain on the thin mono c-Si film.

Polyamides belong to the major class of engineering polymers with very attractive properties but fail in a brittle manner under stress concentrators. PA6/ABS blends are well-established commercial materials due to their stiffness/toughness balance even when stress concentrators are present. The pair PA6/ABS is immiscible and exhibits poor mechanical properties due to unfavorable interactions, thus, an efficient compatibilization is mandatory for practical applications. Deep understanding of the processing-structure-properties interplays requires multiple characterization techniques to provide insights on the impact of the processing/compatibilization on morphology and phases' distribution. In this work an advanced co-localized AFM-Raman strategy was used to study the compatibilization of PA6/ABS blends with SAN-g-Maleic Anhydride. AFM and TEM allowed nanomechanical analysis and characterization of the blends' morphologies. Co-localized AFM-Raman provided new fundamental insights on the compatibilizer's effect on the PA6's γ polymorphic crystallization. The amount and distribution of this γ phase were found to depend on the blending protocol.

Proton-Exchange Membrane Fuel Cells is a promising emission free energy technology. New generation of hybrid membrane for hydrogen fuel cells were produced from commercial sPEEK membranes, chemically and mechanically stabilized with a Sol-Gel (SG) phase. To study the process-structure-properties relationship of our alternative membranes we coupled Atomic Force Microscopy and Raman microspectroscopy on membranes prepared by cryo-ultramicrotomy without epoxy embedding. This paper demonstrates the powerfulness of co-localized AFM-Raman analysis, revealing the inner structure of hybrid membranes. We obtained quantitative data on the diffusion/condensation of SG precursors inside the sPEEK membrane. Co-localized analyses revealed the formation of skin layers with lower SG concentration on both sides of the membrane. The diffusion of species from the SG phase at the cross-section surface was observed at the first step of fabrication (insufficient SG condensation) and disappeared after hydrothermal treatments (improved SG condensation). The nano-mechanical data revealed a densification of the SG phase through the fabrication process.

The optimization of manufacturing processes and the investigation of polymer materials during their life cycle imply an extended knowledge of the physical and chemical properties of the material. T...

Operando Raman spectroscopy and synchrotron X-ray diffraction were combined to probe the evolution of strain in Li-ion battery anodes made of crystalline silicon nanoparticles. The internal structure of the nanoparticles during two discharge/charge cycles was evaluated by analyzing the intensity and position of Si diffraction peaks and Raman TO-LO phonons. Lithiation/delithiation of the silicon under limited capacity conditions triggers the formation of "crystalline core-amorphous shell" particles, which we evidenced as a stepwise decrease in core size, as well as sequences of compressive/tensile strain due to the stress applied by the shell. In particular, we showed that different sequences occur in the first and the second cycle, due to different lithiation processes. We further evidenced critical experimental conditions for accurate operando Raman spectroscopy measurements due to the different heat conductivity of lithiated and delithiated Si. Values of the stress extracted from both operando XRD and Raman are in excellent agreement. Long-term ex situ measurements confirmed the continuous increase of the internal compressive strain, unfavorable to the Si lithiation and contributing to the capacity fading. Finally, a simple mechanical model was used to estimate the sub-nanometer thickness of the interfacial shell applying the stress on the crystalline core. Our complete operando diagnosis of the strain and stress in SiNPs provides both a detailed scenario of the mechanical consequences of lithiation/delithiation in SiNP and also experimental values that are much needed for the benchmarking of theoretical models and for the further rational design of SiNP-based electrodes.

This paper aims at studying the influence of the reinforcement particle size and morphology on the wear resistance properties of NiCrBSi-based composites. Numerous papers have already been written on this subject but almost all of them studied the “conventional” particle size for laser cladding (i.e. between 20 and 200 μm). The objective of this study is to see the influence of coarser reinforcement particles, up to 1.2 mm, and the influence of the morphology (spherical and random shaped) on the coatings erosive and sliding wear resistance. Laser clad coatings were deposited on low carbon steel substrate S235JR with various amounts of WC/W 2 C particles up to 50 vol.%. The coatings were processed by using a 3.8 kW High Power Diode Laser (HPDL). Spherical tungsten carbide particles from 40 μm up to 1200 μm were used in this study as well as random shaped particles from 40 μm to 400 μm. To assess the influence of the reinforcement particle properties on wear properties, wheel tests and pin-on-disk tests were performed on each composition. From this study, it can be concluded that there is an obvious advantage in using larger particles (750–1200 μm) in harsh conditions while smaller particles (40–160 μm) improve the resistance in sliding conditions. The effect of morphology has not been proved significant.

Via SAXS, herein, we studied how a sPEEK microstructure evolves when it is immersed in water at a wide range of temperatures (20-100 °C) and time scales (from a few hours to dozens of days). In particular, we scrutinized the behavior of sPEEK at the temperature and time associated with the appearance of a well-defined nanosegregated morphology. At 80 °C, we observed nanoscale swelling along with smoothing of the water/polymer interface over a long period of time (several days). Herein, two of the main membrane properties, i.e., water uptake and proton conductivity, were studied for different immersion times and temperatures. It was found that the abovementioned properties were remarkably correlated with the evolution of the membrane microstructure, which was partly conserved after drying. The present findings helped us to understand that the thermally activated evolutions observed at both the nanoscale and macroscale were associated with the sPEEK β-relaxation crossover. Therefore, the very different swelling behaviors of sPEEK and Nafion are correlated to the much higher β-relaxation of sPEEK vs. Nafion (75 °C vs. -20 °C - dry state). From a practical viewpoint, this study emphasizes, for membranes alternative to Nafion, the importance and impact of the membrane pretreatment on their functional properties.

This paper presents an in depth study of the moisture influence on reliability and electrical characteristics of SiOC:H low-κ dielectric material. Firstly, TDDB models have been evaluated on material without moisture and Impact Damage model is found to be the most accurate for lifetime estimation. Then, various characterization techniques reveal that moisture provokes a significant decrease of the Time-to-breakdown (TBD) together with major modifications of conduction and breakdown mechanisms. Finally, results suggest that material polarizability modification might play a role in the evidenced premature breakdown.

Crystallization of strontium fresnoite Sr2TiSi2O8 piezoelectric crystals in Sr&ndash, Ti&ndash, Si&ndash, K&ndash, Al&ndash, O parent glasses is investigated with the aim of showing the influence of composition and crystallization conditions on the microstructure and piezoelectric properties of the resulting glass-ceramic. All the investigated conditions lead to a surface crystallization mechanism that induces a preferential orientation of crystal growth in the glasses. Near the surface, all the glass-ceramics obtained exhibit (002) planes preferentially oriented parallel to their faces. Deeper in the specimens, this preferential orientation is either kept or tilted to (201) after a depth of about 300 &micro, m. The measurement of the charge coefficient d33 of the glass-ceramic highlights that surface crystallization induces mirror symmetry in the polarization. It reaches 11 to 12 pC/N and is not significantly influenced by the preferential orientation (002) or (201). High temperature XRD shows the stability of the fresnoite phase in the glass-ceramics up to 1000 &deg, C. Mechanical characterization of the glass-ceramics by impulse excitation technique (IET) highlights that the softening of the residual glass leads to a progressive decrease of Young&rsquo, s modulus in the temperature range 600&ndash, 800 &deg, C. Damping associated to the viscoplastic transition become severe only over 800 &deg, C.

Metal–insulator–metal (MIM) diodes with bulk-limited current conduction asymmetry employing interposed Al2O3 layer in 6-nm-thick HfO2 film have been investigated. The current density is decreased as the Al2O3 layer is located far from the electron injection electrode (i.e., cathode). Also, the work function difference of the electrode does not affect the asymmetry of the MIM diodes. Asymmetry of current conduction is attributed to the control of bulk-limited current conduction by the interposed Al2O3 layer. Physicochemical analysis also confirms the dependence of the location of Al2O3 layer on the bulk-limited current asymmetry.

In this work, aqueous solutions of magnetite nanoparticles (NPs) are studied. Magnetite NPs are very useful in biomedicine for magnetic resonance imaging (MRI), for drug delivery therapy, and also for hyperthermia. In order to predict the NP efficiency in these applications, it is crucial to accurately characterize their size distribution and their magnetization. Magnetometry, through the dependence of NP magnetization on the magnetic induction (MB curve), can provide interesting information on these physical properties. In this work, the extraction of the NP size distribution and magnetization from experimental MB curves of aqueous solutions of magnetite NPs is discussed. The results are compared to TEM and XRD characterizations. It is shown that an expression taking into account the size distribution better fits the results than the commonly used simple Langevin function. The size distributions obtained by magnetometry seem comparable to those obtained by TEM measurements. However, a closer look at the results shows some nonnegligible discrepancies: the size distributions obtained by magnetometry vary with the temperature and are closer to the TEM ones at room temperature. Our study suggests that it could be explained by the nonnegligible anisotropy energy of the NPs at low temperature and the lack of NP Brownian rotation below the freezing point of water. This demonstrates that care must be taken when interpreting the results obtained by magnetometry of magnetite NPs: only the size and size distribution obtained at room temperature should be used.

This paper underlines the damages induced by probing on narrow pads reliability of specifically designed test structures placed on dicing streets and indicates that probing during electrical test steps provokes detrimental cracks diving from the passivation through the BEOL layers providing a path for moisture ingress.

This paper presents a surface acoustic wave (SAW) device able to operate up to 900°C, based on a piezoelectric non-ferroelectric glass-ceramic containing fresnoite crystals. This material is synthesized by a classic glassmaking technique and isothermal crystallization heat treatment. Its properties are measured at high temperatures. Input and output interdigital transducers (IDT) are realized on its surface to generate and receive the SAW. It creates a temperature device working up to 800°C, that will further be modified in pressure or humidity sensors by applying the appropriate sensitive layer between the input and the output IDT.

Alternatives to lead crystal glass were initially selected from CD-ROM ‘interglad’ data, and then elaborated. These samples have properties closer to those of conventional lead crystal, are completely lead free. In this study, vitrifiable mixtures based on silicon, barium, strontium and zinc oxides were melted at 1450 °C, annealed at 580 °C, and characterized by x-ray diffraction, infrared spectroscopy, Raman spectroscopy and Calorimetric Thermal Analysis (DSC). X-ray diffraction confirms the amorphous character of all investigated glasses. The vibration bands are identified by infrared and Raman spectroscopy. These results highlight the influence of glass composition on structural properties. The glass transition temperatures (Tg) were determined by differential scanning calorimetric analysis (DSC). The obtained results vary from 546.8 °C to 632.6 °C, confirming the effect of the composition on the thermal properties.

Gold nanoparticles, capped by 3-mercapto propane sulfonate (Au-3MPS), were synthesized inside a swollen sulfonated poly(ether ether ketone) membrane (SPEEK). The formation of the Au-3MPS nanoparticles in the swollen sPEEK membrane was observed by spectroscopic and microscopic techniques. The nanocomposite containing the gold nanoparticles grown in the sPEEK membrane, showed the plasmon resonance λmax at about 520 nm, which remained stable over a testing period of three months. The size distribution of the nanoparticles was assessed, and the sPEEK membrane roughness, both before and after the synthesis of nanoparticles, was studied by AFM. The XPS measurements confirm Au-3MPS formation in the sPEEK membrane. Moreover, AFM experiments recorded in fluid allowed the production of images of the Au-3MPSatsPEEK composite in water at different pH levels, achieving a better understanding of the membrane behavior in a water environment; the dynamic hydration process of the Au-3MPSatsPEEK membrane was investigated. These preliminary results suggest that the newly developed nanocomposite membranes could be promising materials for fuel cell applications.

The context of the present work is a large research project aiming at manufacturing functionalised surfaces by selected laser treatment with a focused beam [1]. More specifically, this paper aims at showing the possibility of obtaining a dense glass ceramic layer, with controlled microstructure, from a glass powder coating. In the present state of the research, laser scans are performed on glass powder compacts in order to investigate the operating conditions (power, speed and vectorisation) required to achieve the objective. The selected glass belongs to the Sr–Ti–Si–Al–K–O system, its crystalisation leads to a glass–ceramics containing piezoelectric Sr–fresnoite crystals (Sr2TiSi2O8) Maury et al. (2011). The selective laser treatment is carried out by mean of a focused Nd–YVO4 laser beam. Characterisation of the thermal state of the surface during the treatment is performed thank to an IR camera. The surface microstructure is evaluated by X-ray diffraction and scanning electron microscopy. The results presented shows that Sr–fresnoite glass ceramics layers can be processed by applying a two stage process: first the melting of a glass powder to form a dense amorphous layer; then the crystallisation of this layer. However, the microstructures resulting of a crystallisation step performed by mean of a one-scan laser treatment are heterogeneous. IR camera analysis highlights that this heterogeneity is due to thermal profile strongly depending on the position on the scanned surface. Moreover, the high energy scanning conditions required to promote crystallisation make that this later takes place on cooling after surface has been re-melted. Processing by a multi-scan mode (numerous successive rapid scans) seem more suitable. In that case, IR camera analysis shows a homogeneous thermal state of the surface. Additional investigations have to be performed in order to be able to master the relation between the thermal profile and the laser scan parameters.

NiCrBSi/WC composite coatings containing various amounts of WC/W2C particles were laser cladded on low carbon steel substrate S235JR. Coatings were processed using two different laser systems, a 1 kW Nd:YAG and a 3.8 kW high power diode laser (HPDL). Coatings obtained with the Nd:YAG source demonstrate significant changes in the matrix microstructure with WC/W 2 C particle addition. Specific analysis shows the formation of new carbides (W,Cr) x C y and boride phases (W,Cr) x B y resulting from a partial dissolution of the WC/W 2 C particles within the metal matrix. The Brinell macrohardness of the coatings reveals surprisingly low values for coatings containing 10 vol.% and 20 vol.% WC/W 2 C. Through nanoindentation measurements, it is suggested that the low hardness of these new carbide and boride phases most likely counteracts the WC/W 2 C addition and may explain this unexpected behavior. On the contrary, the same coatings deposited using the HPDL source exhibits no change in the microstructure of the NiCrBSi matrix and display an expected monotonic increase of composite hardness with WC/W 2 C amount. It is suggested that the microstructural appearance of new carbide and boride phases may not be related to the type of laser used but to the specific laser energy during the coating process. Contrarily to hardness, measurements show that the erosive wear is marginally affected by the microstructural differences of the coatings. These results demonstrate that evaluating the quality of laser cladded coatings by simply assessing their density and the absence of a crack (as usually done) is insufficient as it does not automatically guarantee reaching optimal mechanical performance.

This work presents an in-depth study of the thermal stability of low-k material in view of intermediate Back-End-Of-Line (iBEOL) for 3D sequential Integration. SiOCH ULK were analyzed after thermal annealing up to 600°C. Moreover, the stability and reliability of this ULK material coupled with W metal in line 1 integration is characterized up to 550°C, 5 $h$ . We have demonstrated that low-k material can support a thermal budget of 500°C, 2h with limited outgassing. This result is fully compatible with 3D sequential integration.

This paper presents an overview of our work on metal-insulator-metal (MIM) structures used for resistive non-volatile resistive (RRAM) or dynamic (DRAM) random access memories. Atomic layer deposition technique is used to grow the insulator layer. ALD allows monolayer thickness precision of deposited layers and flexible in-situ doping capabilities. Thanks to a suitable choice of the bottom, top electrodes and the dielectric, DRAM or RRAM functionality is enabled. It will be shown how we managed to tackle the main challenge in DRAM field where high dielectric constant along with minimum leakage current should be performed. For RRAM, the main challenge is to obtain reversible MIM resistance switching at low power and high Roff/Ron ratio. The switching mechanism in RRAM, usually attributed to oxygen vacancies percolation leading to a conduction path, has been studied with a focus on the role of the electrodes affinity to oxygen and their electron injection efficiency.

Dmitry Grishenkov,1–3 Adrian Gonon,3,4 Eddie Weitzberg,5 Jon O Lundberg,5 Johan Harmark,6 Barbara Cerroni,7 Gaio Paradossi,7 Birgitta Janerot-Sjoberg1–3 1Department of Clinical Science, Intervention, and Technology, Karolinska Institutet, Stockholm, Sweden; 2Department of Medical Engineering, KTH, Royal Institute ofTechnology, School of Technology and Health, Stockholm, Sweden; 3Department of Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden; 4Department of Medicine, Karolinska Institutet, Stockholm, Sweden; 5Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; 6Department of Biosciences and Nutrition, Karolinska Institutet, KTH, Royal Institute of Technology, School of Technology and Health, Stockholm, Sweden; 7Department ofChemical Sciences and Technologies, University of Rome Tor Vergata, Rome,Italy Abstract: The current study describes novel multifunctional polymer-shelled microbubbles (MBs) loaded with nitric oxide (NO) for integrated therapeutic and diagnostic applications (ie, theranostics) of myocardial ischemia. We used gas-filled MBs with an average diameter of 4µm stabilized by a biocompatible shell of polyvinyl alcohol. In vitro acoustic tests showed sufficient enhancement of the backscattered power (20dB) acquired from the MBs’ suspension. The values of attenuation coefficient (0.8dB/cmMHz) and phase velocities (1,517m/s) were comparable with those reported for the soft tissue. Moreover, polymer MBs demonstrate increased stability compared with clinically approved contrast agents with a fracture threshold of about 900kPa. In vitro chemiluminescence measurements demonstrated that dry powder of NO-loaded MBs releases its gas content in about 2hours following an exponential decay profile with an exponential time constant equal to 36minutes. The application of high-power ultrasound pulse (mechanical index =1.2) on the MBs resuspended in saline decreases the exponential time constant from 55 to 4minutes in air-saturated solution and from 17 to 10minutes in degassed solution. Thus, ultrasound-triggered release of NO is achieved. Cytotoxicity tests indicate that phagocytosis of the MBs by macrophages starts within 6–8hours. This is a suitable time for initial diagnostics, treatment, and monitoring of the therapeutic effect using a single injection of the proposed multifunctional MBs. Keywords: microbubbles, contrast agent, ultrasound, nitric oxide, myocardial ischemia

International audience; In this work, foams were obtained by direct foaming of aqueous alumina suspensions containing butyric acid. Butyric acid is incorporated in the suspensions in order to hydrophobize alumina particles, leading to their adsorption at the air/water interface. After setting and drying, wet foams were sintered at 1585 °C for 2 h. The resulting porous samples were characterized in terms of microstructure, mechanical properties and thermal conductivity. Microstructures of sintered alumina foams reveal closed pores surrounded by a thin alumina layer. The microstructure of these macroporous ceramics is related to (i) the composition of the initial suspension (alumina and butyric acid contents) and (ii) the stirring velocity during the foaming process. Macroporous ceramics with pore sizes (d50) ranging from 20 µm to 140 µm and porosities between 25% and 89% were obtained. Three-point bending tests were performed on foams with porosities between 65% and 89%. The results of mechanical tests were analyzed with Weibull statistic. The bending strength values are between 5 MPa and 42 MPa. The Young’s modulus, obtained from 3-point bending tests, decreases with the porosity level according to Gibson–Ashby model. Thermal diffusivity measurements were made with the laser flash technique in order to determine the effective thermal conductivity. Experimental values are significantly higher than the predictions with Landauer’s relation and almost close to Maxwell/Hashin–Shtrikman upper bound.

This paper presents a new approach for the realization of RF switches based on the Conductive Bridging Random Access Memory technology (CBRAM). This promising approach allows the realization of RF switches in an extremely simple manner at low cost. For the first time, an RF switch based on a MIM structure is realized with an insulator layer obtained from a commonly used resin deposited by spin coating. The paper reports a RF switch based on CBRAM and demonstrates a device integration onto plastic circuit board (PCB). The realized switch is validated by experimental measurements for a frequency range up to 1.5 GHz with an activation voltage less than 1 V.

New proton-conducting co-networks were synthesized, characterized and tested as Polymer Exchange Membranes for Fuel Cells application. The membranes were obtained from 2-acrylamido-2-methylpropane sulfonic acid (AMPS) copolymerized with a perfluoropolyether oligomer used as crosslinker (Fluorolink ® FMD700). The structure, the thermo-mechanical behavior, the transport properties and the stability were examined in function of the co-network composition, e.g. increasing amount of conductive AMPS. High proton conductivity (1.10 –3 –5.10 −3 S cm −1 ) was reached at a threshold composition of 10 wt% AMPS, which also corresponds to a significant increase in water sorption. The efficiency of proton transfer was shown to directly correlate to the phase-separated nanostructures. On increasing the AMPS content, hydrophilic clusters embedded in the mechanically-robust FMD700 percolate and a co-continuous 3D morphology is formed. Fuel cells tests performed using the high-AMPS content crosslinked membranes showed behaviors comparable to benchmark Nafion ® under similar conditions, with performances significantly improved when the temperature is increased.

International audience; In this letter, the dielectric properties of rutile TiO2 thin films are studied for metal-insulator-metal capacitor applications. The dielectric constant, the ac conductivity, and the loss tangent are measured in a wide band frequency range, from 1 Hz to 2 GHz. The effect of aluminum doping, as well as the influence of film thickness, on the dielectric properties is presented.

Novel polyimide-organosilicate hybrid films were prepared by sol–gel process from a novel functionalized polyimide with alkoxysilanes as pendant groups that increase the affinity between inorganic and organic phases. The synthesis of this functionalized polyimide was carried out by an esterification reaction of a copolyimide containing carboxylic acid groups with allyl alcohol and subsequent hydrosililation. Tetraethoxysilane was used as precursor of silica in different amounts to obtain hybrid membranes with a silica content of 5, 10 and 20 %. The polymers and hybrid membranes were structural, mechanical and thermally characterized. The 29Si-NMR solid state spectroscopy confirmed that silica was covalently bonded to the polyimide. SEM pictures showed a good dispersion of the silica particles and an amorphous morphology was observed by WAXS. DSC analyses revealed an increase in rigidity with the increase in silica content. The mechanical strength of the hybrid membranes decreased with the silica amount, exhibiting a brittle behavior. The evaluation of the gas permeation properties revealed that the film with the lowest silica content showed the highest permeability coefficients for O2, N2, CH4, and CO2 with 34, 8, 6, and 128 barrers respectively, while all hybrid membranes showed similar permselectivities around 4 and 22 for O2/N2 and CO2/CH4 respectively. The fractional free volume of hybrid membranes determined by positron annihilation lifetime spectroscopy followed the same trend that permeability coefficients, confirming that the gas transport properties are mainly governed by the free volume elements.

This paper presents a new method for manufacturing macroporous ceramics by partial sintering of controlled ceramic powder agglomerates packing. Using this route, the final ceramic material is characterized by a hierarchical porous network that can contain up to three levels of interconnected pores: (i) the voids existing between the agglomerates (typically ≥10 µm in size), (ii) the porosity remaining inside the agglomerates after partial sintering (typically ≈100–1000 nm in size), (iii) the pores that may exist within the initial ceramic particles (typically

In this Letter, we evaluate the so-called forming process of virgin HfO2 cells under ac and dc stress by capacitance–voltage measurements. It is found that the ac nonlinearity is higher than the dc one. This is related to the dispersive nature of hopping conduction according to the electrode polarization model. Under short stress times, both capacitance and current are unaffected. However, after longer stress times, no recovery is observed. Consequently, the current increases and a plateau appears in the capacitance. The observed degradation is consistent with the RRAMs-forming process. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Spark Plasma Sintering presents many advantages in comparison with more conventional sintering techniques. Nevertheless, one of its main drawbacks is the heterogeneity of temperature field during the dwell of the temperature cycle, giving heterogeneous final microstructure. In this article, we propose to optimize the temperature field in the compact in order to obtain an almost homogeneous temperature only by modifying the tools dimensions. This optimization is based on the use of a coupled thermoelectric finite element model of the process. Finally, we present the sintering conditions influencing the optimization parameter.

This work is focused on the investigation of Au/high k/TiN stacks for Resistive Random Access Memories. A screening of high k oxides, commonly used in advanced metal gates, such as HfO2 and ZrO2, is proposed. These oxides were grown on TiN electrodes using Atomic Layer Deposition and Plasma Enhanced Atomic Layer Deposition. The morphological and structural properties of the films were studied as a function of deposition temperature, film thickness and/or annealing using Atomic Force Microscopy, Grazing Incidence X-ray Diffraction and Attenuated Total Reflectance. An amorphous to crystalline transformation was observed with thickness for HfO2 and ZrO2, with deposition temperature for HfO2 from 300 to 350 °C, and with annealing in N2 for 1 h at 400 °C for ZrO2. According to density measurements obtained using X-ray Reflectometry, HfO2 and ZrO2 are suspected to be stoichiometric whatever the thickness. The film stoichiometry was confirmed using X-ray Spectroscopy. Current–voltage measurements were performed on Au/high k/TiN, where Au and TiN are top and bottom electrodes, respectively. Whatever the high k material, the crystallization increases with thickness or/and temperature without any significant modification of the SET operation. The film annealing, which was proposed as an alternative way to crystallize ZrO2, may cause a modification of the interfaces, leading to a decrease of the switching performance.

In this paper, TiO2 layers grown on RuO2 by atomic layer deposition (ALD) using tetrakis (dimethyla-mino) titanium (TDMAT) and either oxygen plasma or H2O as oxygen source were analyzed using X-ray diffraction (XRD), Raman spectroscopy, and depth-resolved X-ray Photoelectron spectroscopy (XPS). The main objective is to investigate the surface chemical reactions mechanisms and their influence on the TiO2 film properties. The experimental results using XRD show that ALD deposition using H2O leads to anatase TiO2 whereas a rutile TiO2 is obtained when oxygen-plasma is used as oxygen source. Depth-resolved XPS analysis allows to determine the reaction mechanisms at the RuO2 substrate surface after growth of thin TiO2 layers. Indeed, the XPS analysis shows that when H2O assisted ALD process is used, intermediate Ti2O3 layer is obtained and RuO2 is reduced into Ru as evidenced by high resolution transmission electron microscopy. In this case, there is no possibility to re-oxidize the Ru surface into RuO2 due to the weak oxidation character of H2O and an anatase TiO2 layer is therefore grown on Ti2O3. In contrast, when oxygen plasma is used in the ALD process, its strong oxidation character leads to the re-oxidation of the partially reduced RuO2 following the first Ti deposition step. Consequently, the RuO2 surface is regenerated, allowing the growth of rutile TiO2. A surface chemical reaction scheme is proposed that well accounts for the observed experimental results.

International audience; Graphene, a two dimensional material with remarkable electronic properties, has attracted a huge interest among scientist during the last decade. We report the fabrication of Graphene-HfO2-based resistive RAM memories. We insert graphene layers between the oxide layer and the gold top electrode resulting in stabilization of a low resistance state stability without applied voltage, contrary to behaviour observed for identical graphene free memory devices. Graphene here is used as an oxygen reservoir and contribute to the switching mechanism. (C) 2016 Elsevier B.V. All rights reserved.

Dielectric spectroscopy is carried out for intrinsic and aluminum-doped TiO2 rutile films which are deposited on RuO2 by the atomic layer deposition technique. Capacitance and conductance are measured in the 0.1 Hz–100 kHz range, for ac electric fields up to 1 MVrms/cm. Intrinsic films have a much lower dielectric constant than rutile crystals. This is ascribed to the presence of oxygen vacancies which depress polarizability. When Al is substituted for Ti, the dielectric constant further decreases. By considering Al-induced modification of polarizability, a theoretical relationship between the dielectric constant and the Al concentration is proposed. Al doping drastically decreases the loss in the very low frequency part of the spectrum. However, Al doping has almost no effect on the loss at high frequencies. The effect of Al doping on loss is discussed through models of hopping transport implying intrinsic oxygen vacancies and Al related centers. When increasing the ac electric field in the MVrms/cm rang...