Correlation between mechanical and microstructural properties of molybdenum nitride thin films deposited on silicon by reactive RF magnetron discharge

Molybdenum nitride thin films were deposited on (100) silicon substrates by R.F. magnetron sputtering of a Mo target in a (Ar-N2) gas mixtures. The films were studied by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray diffraction. The nanomechanical properties have been determined by nanoindentation and Peak-Force Quantitative Nanomechanical Mapping (PF-QNM). The total internal stresses were determined by curvature measurements and the Stoney formula. As thin film composition influences the morphology, the stress state and the mechanical properties, modifications are expected in this study where the nitrogen content is tuned. The film exhibits a polycrystalline structure with preferred orientation along (111) plane. The increase of the nitrogen content in the coating (N/Mo =1.1) induces a broadening of the full width at half maximum (FWHM) of the (111) diffraction peak, which is attributed to the presence of smaller crystallites. The residual stress and mechanical properties variation were correlated to the structural transition from γ-Mo2N to hexagonal and cubic MoN. The results show a good agreement between the nanomechanical properties obtained by nanoindentation and PF-QNM

Synthesis by ATRP of Polystyrene-b-Poly(4-vinylpyridine) and Characterization by Inverse Gas Chromatography

A linear diblock copolymer [Polystyrene-b-Poly(4-vinyl-pyridine)] (PS-b-P4VP) was successfully prepared through Atom Transfer Radical Polymerization (ATRP). This synthesis is performed in two successive steps: using the (1-bromoethyl) benzene as initiatorand and Hexamethyl tris [2(dimethylamino)ethyl] amine as ligands in a protic solvent. The first step of the synthesis allows the realization of block polystyrene having a terminal function; however, Bromine (Br) permits the grafting of the second successive block P4VP. RMN -1H demonstrates that the P4VP block has been grafted onto the PS block. The molecular weight of PS-b-P4VP is determined by size exclusion chromatography, and its thermal stability is examined by TGA. The surface and the thermodynamic properties of this copolymer are studied by inverse gas chromatography (IGC). The new Hamieh Model shows that the synthesized copolymer PS-P4VP has an amphoteric behavior with rather very basic character that is six times stronger than acidic character (in Lewis terms), reflected the presence of acidic and basic groups in the structure of the PS-P4VP copolymer, more particularly the presence of benzenic, methyl and vinylpyridine groups

Bacterial Colonization of Low‐Wettable Surfaces is Driven by Culture Conditions and Topography

Effect of surface low‐wettability on bacterial colonization has become a prominent subject for the development of antibacterial coatings. However, bacteria's fate on such surfaces immersed in liquid as well as causal factors is poorly understood. This question is addressed by using a range of coatings with increasing hydrophobicity, to superhydrophobic, obtained by an atmospheric plasma polymer method allowing series production. Chemistry, wettability, and topography are thoroughly described, as well as bacterial colonization by in situ live imaging up to 24 h culture time in different liquid media. In the extreme case of superhydrophobic coating, substrates are significantly less colonized in biomolecule‐poor liquids and for short‐term culture only. Complex statistical analysis demonstrates that bacterial colonization on these low‐wettable substrates is predominantly controlled by the culture conditions and only secondary by topographic coating's properties (variation in surface structuration with almost constant mean height). Wettability is less responsible for bacterial colonization reduction in these conditions, but allows the coatings to preserve colonization‐prevention properties in nutritive media when topography is masked by fouling. Even after long‐term culture in rich medium, many large places of the superhydrophobic coating are completely free of bacteria in relation to their capacity to preserve air trapping

Etude de guides d'onde polymères fluorés par voie plasma et développement de nouveaux capteurs photoniques à base de polyaniline

Ce travail, qui s'inscrit dans une thématique scientifique propre à la fonctionnalisation des polymères pour de nouveaux capteurs optiques basés sur des polymères conducteurs et dédiés à la détection de gaz potentiellement dangereux, a pour but à la fois de diminuer les pertes optiques des guides d onde polymères via la fonctionnalisation par plasma froid et de développer de nouveaux micro-capteurs photoniques à base de polyaniline intégrée sur des guides d onde polymères et dédiés à la détection d ammoniac. Une nouvelle technique, basée sur le traitement de surface par plasma froid, a été utilisée pour diminuer les pertes optiques en propagation dans les guides d onde du polymère SU-8. Deux types de gaz plasmagènes ont été utilisés : CF4 pur et le mélange CF4/H2. L optimisation des paramètres de traitement plasma (temps de traitement, puissance RF, débit de gaz) a permis d obtenir une fluoration maximale en diminuant la dégradation de la surface de polymère. Grâce à cette nouvelle technique, les pertes optiques ont diminué de 60% dans le domaine des télécoms. La diminution des pertes optiques est due à la substitution des liaisons C-H du polymère SU-8 par des liaisons C-Fx (x =1-3) moins absorbantes dans le domaine des télécoms. Le contrôle de la chimie de la phase plasma par l ajout d hydrogène a permis d améliorer la fluoration du polymère, améliorant ainsi la transmission optique des guides d onde polymères. Dans une seconde partie, des capteurs en optique conventionnelle dédiés à la détection d ammoniac, basés sur la variation de l absorbance optique de la couche sensible, ont été développés. Ainsi, différentes couches sensibles ont été élaborées et caractérisées en absence et en présence d ammoniac : la polyaniline pure élaborée par voie chimique, la polyaniline composite (PANI/SU-8, PANI/PMMA) et la polyaniline élaborée par voie plasma. La dispersion de la polyaniline dans la matrice d un polymère a permis d améliorer les performances des capteurs optiques tout en conservant sa sensibilité et sa sélectivité à l ammoniac. Enfin, une famille de nouveaux micro-capteurs photoniques intégrés sur des guides d onde monomodes en polymère SU-8 et dédiés à la détection d ammoniac a été développée et caractérisée. Nous avons ainsi validé le concept de sensibilité optique de matériau à un gaz via la sonde ou queue évanescente. Trois micro-capteurs photoniques ont été réalisés : micro-capteurs à base de polyaniline composite, à base de polyaniline élaborée par voie plasma ou basés sur une architecture multicouches. Le montage de caractérisation sous gaz développé au laboratoire autour du banc de micro-injection photonique a permis de mesurer des variations de la puissance de la lumière guidée en sortie des micro-capteurs et de détecter des concentrations d ammoniac aussi faibles que 92 ppm. L étude des micro-capteurs en présence d ammoniac a montré que ces structures ont une sensibilité importante et sont rapidement régénérées à température ambiante.A new technique for the control of surface properties and optical transmission losses of SU-8 polymer waveguide based on radio-frequency plasma treatment is studied. Two types of plasma have been used: CF4 and CF4/H2 mixtures. It was found that the functionalization degree depends on process parameters such as gas phase, treatment duration, and discharge power. The optical losses decrease after plasma treatment and can be reduced up to 60 % in the telecom region (1304 nm). The observed decrease of optical losses due to propagation in Si/SiO2/fluorinated SU-8 planar waveguides has been correlated to the surface properties of fluorinated polymer. The decrease of the optical losses can be due to the substitution of the C-H bonds by CFx (x=1-3) bonds which are less absorbing in the telecom region. The control of the chemical plasma phase by the hydrogen addition improves fluorination of polymer, thus improving the optical transmission of the polymeric waveguides. In second part, optical ammonia gas sensors, based on the variation of the optical absorbance of the sensitive layer, were developed. Thus, various sensitive layers were elaborated and characterized in the absence and in the presence of ammonia gas: pure polyaniline (PANI) synthesized by chemical way, the PANI composites (PANI/SU-8, PANI/PMMA) and PANI synthesized by plasma technique (PECVD). The sensors present significant absorbance variations upon exposure to ammonia gas at room temperature. The dispersion of polyaniline in the polymer matrix improves the performances of the optical sensors while preserving its sensitivity and its selectivity to ammonia gas. Finally, a new family of photonic ammonia sensors integrated on SU-8 polymer waveguide was designed and developed. We have validated the concept of optical sensitivity of material to a gas via the probe or evanescent field. Three photonic micro-sensors were developed: micro-sensors based on polyaniline composite, plasma-polymerized polyaniline and sensors based on a multi-layer architecture. The sensing properties of the photonic sensors to ammonia at room temperature were studied. After exposed to ammonia, a significant change in the guided light output power of the photonic sensors is observed. Compared with the conventional optical ammonia sensor based on absorption spectroscopy, the integrated optical sensor is more sensitive to ammonia.LE MANS-BU Sciences (721812109) / SudocSudocFranceF

Stabilité de revêtements nanoparticulaires

Stabilité de revêtements nanoparticulaire

New sensitive layer based on pulsed plasma-polymerized aniline for integrated optical ammonia sensor.

International audienceA new integrated optical sensor based on plasma-polyaniline sensitive layer for ammonia detection is designed and developed. The sensor is based on polyaniline elaborated by the plasma technique (Plasma Enhanced Chemical Vapor Deposition, PECVD) and deposited on a small section of a single-mode planar SU-8 waveguide. The sensing properties of the integrated optical sensor to ammonia at room temperature are presented. A significant change in the guided light output power of the sensor is observed after exposition to ammonia gas. This new ammonia sensor exhibits fast response and recovery times, good reversibility and repeatability. The metrological parameters (sensitivity, response time and recovery time) of the sensor are strongly influenced by the interaction length (length of sensing region), the type of dopant and the light polarization. The sensor has a logarithmic linear optical response within the ammonia concentration range between 92 and 4618ppm

Development of an optical ammonia sensor based on polyaniline/epoxy resin (SU-8) composite.

International audiencePolyaniline (PANI)/glycidyl ether of bisphenol A (SU-8) composite film is elaborated in order to detect ammonia gas. These composite films are characterized by ultraviolet-visible (UV-vis) spectroscopy, Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The sensitivity to ammonia is measured by optical absorption changes. The ammonia sensing properties of PANI/SU-8 composite films are studied, and then are compared to pure PANI films elaborated by chemical way. Experimental results show that the PANI/SU-8 optical sensor has simultaneously a rapid response to ammonia gas and regenerates easily, that is advantageous compared to pure PANI films

A new evanescent wave ammonia sensor based on polyaniline composite.

International audienceA single-mode TE(0)-TM(0) optical planar waveguide ammonia sensor based on polyaniline/polymethyl methacrylate (PANI/PMMA) composite is designed and developed. The sensing properties of the photonic sensor to ammonia at room temperature are studied. A significant change is observed in the guided light output power of the sensor after it is exposed to ammonia gas. The metrological parameters (sensitivity, response time and recovery time) of the sensor are strongly influenced by the interaction length (length of sensing region). Compared with the conventional optical ammonia sensor based on absorption spectroscopy, the integrated optical sensor is more sensitive to ammonia

Design and sensing properties of an integrated optical gas sensor based on a multilayer structure.

International audienceIn this paper, a new multilayer integrated optical sensor (MIOS) for ammonia detection at room temperature is proposed and characterized. The sensor is integrated on a single-mode TE0-TM0 planar polymer waveguide and based on polyaniline (PANI) sensitive material. A polymethyl methacrylate (PMMA) passive layer is deposited between the waveguide core and PANI sensitive layer in order to decrease optical losses induced by evanescent wave/sensitive material coupling. The design of this new sensor is discussed. Moreover, in order to investigate the feasibility of this sensor, the sensing properties to ammonia at room temperature are studied. A significant change is observed in the guided light output power after the sensor is exposed to ammonia gas, due to PANI absorption coefficient variation. This new ammonia sensor shows fast response and recovery times, good reversibility and repeatability. The metrological parameters (sensitivity, response time and recovery time) of the sensor are strongly influenced by the interaction length (length of sensing region) and the PANI forms (doped and dedoped). The sensor has a logarithmic linear optical response within the ammonia concentration range between 92 to 4618 ppm. These experimental results demonstrate that the MIOS structure presents a potential innovation to elaborate integrated optical sensor based on non transparent (opaque) sensitive material

Study of the surface fluorination of SU-8 polymer film through RF plasma treatment and its application to passive optical waveguide

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