Anisotropic surface properties of micro/nanostructured a-C:H:F thin films with self-assembly applications

The singular properties of hydrogenated amorphous carbon (a-C:H) thin filmsdeposited by pulsed DC plasma enhanced chemical vapor deposition (PECVD), such as hardness and wear resistance, make it suitable as protective coating with low surface energy for self-assembly applications. In this paper, we designed fluorine-containing a-C:H (a-C:H:F) nanostructured surfaces and we characterized them for self-assembly applications. Sub-micron patterns were generated on silicon through laser lithography while contact angle measurements, nanotribometer, atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the surface. a-C:H:F properties on lithographied surfaces such as hydrophobicity and friction were improved with the proper relative quantity of CH4 and CHF3 during deposition, resulting in ultrahydrophobic samples and low friction coefficients. Furthermore, these properties were enhanced along the direction of the lithographypatterns (in-plane anisotropy). Finally, self-assembly properties were tested with silicananoparticles, which were successfully assembled in linear arrays following the generated patterns. Among the main applications, these surfaces could be suitable as particle filter selector and cell colony substrate

Nanostructured DLC coatings for self-assembly applications

The singular characteristics of diamond-like carbon (DLC) thin films, concerning tribological and surfaces properties, are suitable for self-assembly applications. Usually, DLC thin films have been developed as protective coatings for sliding surfaces with relative motion. But, DLC coatings deposited on nanostructured surfaces also provide new potential for self-assembly applications. In particular, the addition of fluorine during the deposition of DLC deposited by pulsed DC plasma enhanced chemical vapor deposition (PECVD) has a significant effect on the surface energy and tribological characteristics, which accelerates the mechanisms involved in self-assembly processes. Among the multiple applications of DLC coatings we also found their biocompatibility and antithrombogenicity. Such properties make them candidates for a number of medical applications where wear-resistant coatings, such as prosthesis, or simply biocompatible parts are required

White paper on the future of plasma science and technology in plastics and textiles

International audienceThis white paper considers the future of plasma science and technology related to the manufacturing and modifications of plastics and textiles, summarizing existing efforts and the current state-of-art for major topics related to plasma processing techniques. It draws on the frontier of plasma technologies in order to see beyond and identify the grand challenges which we face in the following 5–10 years. To progress and move the frontier forward, the paper highlights the major enabling technologies and topics related to the design of surfaces, coatings and materials with nonequilibrium plasmas. The aim is to progress the field of plastics and textile production using advanced plasma processing as the key enabling technology which is environmentally friendly, cost-efficient, and offers high-speed processing

CORROSION DE VERRES DE SILICATE ANALYSE TEXTURALE DE LA COUCHE D'ALTERATION

Thèse réalisée entre 1997 et 2001 au Laboratoire Des Verres (LDV - UMR 5587) devenu après 2005 le Laboratoire des Colloïdes, Verres et Nanomatériaux (LCVN - UMR 5587) à l'Université de Montpellier II.We have studied the kinetic and the texture evolution of the corroded layer that forms on glass surfaces exposed to acidic solutions. The corroded layer is depleted in alkali cations and is produced by an ion exchange mechanism. It is porous and shows a lower refractive index than the one of the bulk glass. Spectroscopic ellipsometry allows determining the thickness of the layer and its refractive index. Several other techniques have been developed for characterizing the corrosion behaviour of glass surfaces: porosity is thus investigated by adsorption-desorption of nitrogen; the thickness and the composition of the layer are studied by secondary ion mass spectroscopy (S.I.M.S.); sodium concentration in the solution has been analyzed by atomic absorption. This study shows the importance of leaching conditions and glass preparation. The type of drying employed is susceptible to modify the texture and the structure of the layer. The layers produced in the early stages of the leaching process are not easily detectable. The different results lead however to the same conclusion: after a strong increase of porosity, a densification of the layer is observed with increasing time. The evolution of the layer texture could therefore modify the kinetic of the glass corrosion.Nous avons étudié la cinétique de formation et l'évolution de la texture de la couche corrodée qui se forme à la surface d'un verre soumis à un bain acide. La couche corrodée est une couche partiellement désalcalinisée produite par échange ionique. Elle est poreuse et se caractérise par un indice de réfraction inférieur à celui du verre sain. L'ellipsométrie spectroscopique permet de déterminer l'épaisseur de la couche et son indice. D'autres techniques expérimentales complètent l'analyse : la porosité est ainsi caractérisée par adsorption-désorption d'azote ; l'épaisseur et la composition de la couche, par sonde ionique (S.I.M.S.); la quantité de sodium relâché dans la solution, par spectrométrie d'absorption atomique. Cette étude a mis en évidence l'importance des conditions de lixiviation et de préparation du verre. Le type de séchage employé est susceptible de modifier la texture et la structure de la couche. La corrosion à court terme ne produit pas des couches facilement détectables. Les différentes techniques d'analyse conduisent cependant à la même conclusion : après une forte augmentation de la porosité, on observe une densification de la couche au cours du temps. L'évolution de la texture de la couche modifierait alors la cinétique de corrosion du verre

Corrosion de verres de silicate (analyse texturale de la couche d'altération)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Photonic characteristics of Langmuir-Blodgett self-assembled monolayers of colloidal silica particles

Monodispersed colloidal crystals based on silica sub-micrometric particles were synthesized using the Stöber-Fink-Bohn process. The control of nucleation and coalescence result in improved characteristics such as high sphericity and very low size dispersion. The resulting silica particles show characteristics suitable for self-assembling across large areas of closely-packed 2D crystal monolayers by an accurate Langmuir-Blodgett deposition process on glass, fused silica and silicon substrates. Due to their special optical properties, colloidal films have potential applications in fields including photonics, electronics, electro-optics, medicine (detectors and sensors), membrane filters and surface devices. The deposited monolayers of silica particles were characterized by means of FESEM, AFM and optical transmittance measurements in order to analyze their specific properties and characteristics. We propose a theoretical calculation for the photonic band gaps in 2D systems using an extrapolation of the photonic behavior of the crystal from 3D to 2D. In this work we show that the methodology used and the conditions in self-assembly processes are decisive for producing high-quality two-dimensional colloidal crystals by the Langmuir-Blodgett technique

Water Induced Surface Reconstruction of the Oxygen (2x1) covered Ru(0001)

Low temperature scanning tunneling microscopy (STM) and density functional theory (DFT) were used to study the adsorption of water on a Ru(0001) surface covered with half monolayer of oxygen. The oxygen atoms occupy hcp sites in an ordered structure with (2x1) periodicity. DFT predicts that water is weakly bound to the unmodified surface, 86 meV compared to the ~;;200 meV water-water H-bond. Instead, we found that water adsorption causes a shift of half of the oxygen atoms from hcp sites to fcc sites, creating a honeycomb structure where water molecules bind strongly to the exposed Ru atoms. The energy cost of reconstructing the oxygen overlayer, around 230 meV per displaced oxygen atom, is more than compensated by the larger adsorption energy of water on the newly exposed Ru atoms. Water forms hydrogen bonds with the fcc O atoms in a (4x2) superstructure due to alternating orientations of the molecules. Heating to 185 K results in the complete desorption of the water layer, leaving behind the oxygen honeycomb structure, which is metastable relative to the original (2x1). This stable structure is not recovered until after heating to temperatures close to 260K