Study of tungsten films deposited by DC sputtering dedicated to integrated heaters

International audienceIn order to realize cost-effective semiconductor gas sensors, the authors have studied the feasibility of replacing platinum by tungsten for the metallic layer of heaters in a moderate temperature range (25-400 degrees C). Tungsten films were deposited on silicon substrates by direct current magnetron sputtering in argon gas. The deposition of tungsten films was investigated at various working gas pressures to modify the microstructure. The results have shown that low-stressed films showed a good adhesion to silicon substrates. Resistivity values as low as 27 mu Omega cm were obtained for 600 nm films deposited at low argon pressure. After a thermal treatment at 500 degrees C for 30 min., no resistivity variation occurred for films deposited at low argon pressure. Finally, three different structures of tungsten heaters were elaborated by using an optical lithography technique and tested for 300 h at 400 degrees C. (C) 2017 American Vacuum Society

A new calorimetric technique for phase change materials and its application to alkane-based PCMs

The correct determination of the phase transition behaviour of phase change materials (PCMs) is paramount for assessing their application potential. In this work, the merits of a novel calorimetric technique, Peltierelement- based adiabatic scanning calorimetry (pASC), for PCM characterisation are investigated, especially in comparison with the commonly-used differential scanning calorimeter (DSC). A comparative study of two alkanebased PCMs, the commercial mixture RT42 and the pure alkane tricosane (C23) with these two techniques shows that pASC provides data at much higher resolution than DSC, due to its operation in thermodynamic equilibrium. Specifically the rate-dependence and deformation that is inherent to DSC experiments is absent in pASC. In addition, the enthalpy of the PCM is directly obtained. pASC results easily conform to the accuracy limits that are proposed in literature for the transition temperature and storage capacity of PCMs.status: publishe

Laser-induced breakdown spectroscopy imaging for material and biomedical applications: recent advances and future perspectives

International audienceNo abstract availabl

Laser-induced breakdown spectroscopy imaging for material and biomedical applications: recent advances and future perspectives

International audienceNo abstract availabl

Nuclear Magnetic Resonance and Calorimetric Investigations of Extraction Mode on Flaxseed Gum Composition

We discussed about the influence of extraction mode on the flaxseed gums composition and their thermal stabilities. In order to do so, flaxseed gum was extracted by both classical magnetic stirring method and ultrasonic-assisted extraction (UAE). As a function of time, protein content, gum yield, pH values were evaluated and samples were characterized by 1H and 13C nuclear magnetic resonance (NMR) experiments as well as scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The flaxseed gum extracted in aqueous solution correspond to a mixture of different components, including polysaccharides, proteins and sometimes lignan derivatives. It is found that the protein and gum contents increase with the extraction duration for both the ultrasonic assisted and the traditional extraction while the pH decreases at the same time. As expected, compared to traditional magnetic stirring method, ultrasonic assisted extraction method can significantly enhance the yield of polysaccharides, lignans and proteins. The variation of pH is correlated to the increase of lignan molecules in the extracted samples. For thermic methods, SEM experiments showed that lignan derivatives which ester-bonded to polysaccharides associated to proteins are responsible to the formation of globular aggregates. Supplementary rod-like molecular organization were obtained from UAE and questions on the nature of the amphiphilic mesogen carbohydrate structures

Orientation of 4- n -octyl-4′-cyanobiphenyl molecules on graphene oxide surface via electron–phonon interaction and its applications in nonlinear electronics

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Hybrid thin Films based Phototransistor Optimized by Dynamic Floating Film Transfer Method

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IMAGERIE LIBS : AUX PORTES DE LA CLINIQUE

International audienceL'étude de la dérégulation des métaux au sein des tissus biologiques intéresse de plus en plus le monde médical car une répartition anormale des métaux est une information importante qui peut contribuer au diagnostic clinique, et orienter le choix du traitement pour de nombreuses pathologies. En tant que méthode d’analyse élémentaire «tout optique », l’imagerie LIBS (laser-induced breakdown spectroscopy) est un candidat idéal pour étudier la composition élémentaire des tissus humains

Charge transport in phenazine-fused triphenylene discotic mesogens doped with CdS nanowires

International audienceWe report the synthesis of oleylamine capped CdS nanowires and we have dispersed a small optimized amount of these NWs in the Col h phase of a recently synthesized phenazine-fused-triphenylene discotic liquid crystal to understand the temperature-dependent charge transport

Dual photoluminescence and charge transport in an alkoxy biphenyl benzoate ferroelectric liquid crystalline-graphene oxide composite

An optimized concentration of graphene oxide (GO) has been dispersed in a ferroelectric liquid crystalline (FLC) material namely 4-(octyloxy)-[1,1-biphenyl]-4-yl 4-(heptan-2-yloxy)benzoate, to prepare a FLC-GO composite. Temperature dependent photoluminescence (PL) measurements for the FLC-GO composite were conducted between 30-100 degrees C. We observed a superlinear increase in the PL with increasing temperature. The time resolved luminescence study exhibits a bi-exponential decay time with a shorter life time for the FLC-GO composite and confirms the surface energy transfer from GO to FLC. Charge transport and current-voltage (I-V) characteristics for the FLC-GO composite have been investigated at ambient conditions by using current sensing atomic force microscopy. For the FLC-GO composite, critical diode like nonlinear I-V curves have been obtained in which the charge transport is assigned to the thermally active intermolecular hopping at room temperature. The FLC material yields ionic charge mobilities of 1.45 x 10(-5), 1.26 x 10(-5) and 9.83 x 10(-6) cm(2) V-1 s(-1) in isotropic, chiral nematic (N*) and chiral smectic C (SmC*) phases. The dispersion of GO significantly enhances the ionic mobility in the composite which was observed to be 2.71 x 10(-4), 2.69 x 10(-4) and 2.65 x 10(-4) cm(2) V-1 s(-1) for the aforementioned phase sequence. Physical interactions between GO and FLC molecules were confirmed by FTIR and polarized optical microscopy. In-plane coupling between the orientation of GO and the long molecular axis of the FLC molecules remarkably enhances the band intensity of C?O, ?C-H, COO, C-O and C-H vibrations. The size of multi-domain fan texture in the SmC* phase has been enhanced after the dispersion of GO. The cobweb like networking in the oily streaks texture of the N* phase confirms the interesting molecular architecture via planar anchoring between FLC molecules and GO. This work opens new avenues towards applications in pico-ampere current-regulated electronic devices and opto-electronics