High Resolution SEM: a tool to study membrane selectivity from its production to its end-of-life

International audienceno abstrac

Positive- and negative-tone structuring of crystalline silicon by laser-assisted chemical etching

International audienceWe demonstrate a structuring method for crystalline silicon using nanosecond laser internal irradiation followed by chemical etching. We show a dramatic dependence of the etch rate on the laser-writing speed. Enhanced isotropic etch rates of silicon by laser-induced internal damage were recently demonstrated with strong acids, but our results add the possibility to obtain reduced etch rates leading to different topographies. Material analyses indicate the possibility to efficiently produce high-aspect ratio channels, thanks to laser-induced porosities, as well as silicon micro-bumps due to highly stressed regions. This holds promises for fabricating microfluidic, photovoltaic, and micro-electromechanical systems

Tungsten dust in fusion tokamaks: relevant dust laser production, characterization and behaviour under tritium loading

15th International Conference on Plasma-Facing Materials and Components for Fusion Applications (PFMC), Aix en Provence, FRANCE, MAY, 2015International audienceIn this paper, production and study of tokamak relevant W particles is presented. Existing tokamak-produced dust being very scarce, extensive study of such nano-particles with high specific surface area (SSA) and sub micron size requires a specific and efficient alternative production technique, in order to obtain relevant particles to study. We present our production and collection setup based on pulsed laser ablation on bulk ITER-grade tungsten, and the various parameters impacting on the collected dust morphology and properties. We observed that optimum gas pressure is required to control the laser-induced plasma properties and favour the production of tungsten nano-particles with high SSA. The laser pulse duration is also a key parameter to limit the generation of tungsten liquid droplets during the ablation process. The nano-particules structure and general aspect are characterized via scanning electron microscopy and transmission electron microscopy. Lastly, this dust produced by laser ablation is loaded with tritium by gas exposure, and its retention capability and long-term evolution addressed and compared to metallurgically produced W powders with homogeneous size distribution

Two-photon excited fluorescence of BF2 complexes of curcumin analogues: toward NIR-to-NIR fluorescent organic nanoparticles

International audienc

Deposition of gold nanofeatures on silicon samples by field-induced deposition using a scanning tunneling microscope

International audienceGold islands of diameter as small as 15 nm and 6 nm high were deposited on a standard silicon ͑100 surface by field-induced deposition using a scanning tunneling microscope operating with Pt or W tips coated by a gold film. Gold atoms are transferred by applying to the sample negative voltage pulses of few volts in magnitude, and of some tens of microseconds in duration. The scanning tunneling microscope tip morphology and composition have been analyzed systematically by field-emission gun scanning electron microscope plus energy dispersive x-ray ͑EDX microanalysis before and after its use for lithography. The deposits composition have also been analyzed by EDX. Finally, preliminary results on trials of direct bonding of microscopic contact leads are presented

Copper red glazes: a coating with two families of particles

Abstract In order to explain the origin of the deep red color of copper glazes on ceramics, a ceramist has elaborated, by firing under reducing atmosphere, a significant number of tiles. The analysis of the structure and composition of a representative sample by TEM and EELS, followed by an optical characterization and an optical modeling using the radiative transfer approach (four-flux model) have enabled a comprehensive explanation of the origin of the color in these glazes. The presence of two families of copper nanoparticles in the vitreous matrix. The first, purely absorbing, of diameter 10-50 nm, essentially creates color by a substractive process. The second, due to its larger diameter, 100 nm or more, mainly acts on color by scattering of the visible light. Both act competitively in the layer. A color chart of all the hues which can be reached by this technique has eventually been theoretically calculated. 1