Hydrodésulfuration : étude comparative de catalyseurs Co-MoS2 / alumine

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Hydrodesulfurization catalysts: Promoters, promoting methods and support effect on catalytic activities

International audienc

Etching issues with High-K Metal Gate stacks for CMOS 28nm technology

International audienc

Advanced backside sample preparation for multi-technique surface analysis

Backside sample preparation is a well-known method to help circumvent undesired effects and artifacts in the analysis of a sample or device structure. However it remains challenging in the case of thin layers analysis since only a fraction oRelax;f the original sample must remain while removing most or all of the substrate and maintaining a smooth and flat surface suitable for analysis. Here we present a method adapted to the preparation of ultrathin layers grown on pure Si substrates. It consists in a mechanical polishing up to a few remaining microns, followed by a dedicated wet etch. This method can be operated in a routine fashion and yields an extremely flat and smooth surface, without any remaining Si from substrate. It therefore allows precise analysis of the layers of interests with various characterization techniques

Quantitative depth profiling of ultrathin high-k stacks with Full Spectrum ToF-SIMS

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Intrinsic potential of alumina-supported CoMo catalysts in HDS: Comparison between gamma c, gamma T, and delta-alumina

RAFFINAGE+DLA:CRO:LMA:MVRMoS2 catalysts were firstly prepared over three different alumina supports gamma c-Al2O3, gamma T-Al2O3, and delta-Al2O3 with the same Mo loading per nm(2). Then, using various deposition methods and different Co-precursors as Co(NO3)(2), Co(acac)(2) and Co(CO)(3)NO, Co-promoted MoS2 catalysts were obtained. The different catalytic systems were tested in hydrodesulfurization (HDS) reactions of thiophene and 4.6-dimethyldibenzothiophene (4,6-DMDBT) under atmospheric and high pressure (4 MPa), respectively. For the non-promoted catalysts, we observed for delta-alumina supported system a higher intrinsic catalytic activity than for gamma c-Al2O3 and gamma T-Al2O3. For the Co-promoted systems, the use of cobalt organometallic complex allowed obtaining catalysts which exhibit higher intrinsic activity than the catalysts prepared by impregnation of Co inorganic salts on supported Mo sulfide. Furthermore, the intrinsic catalytic activities of promoted systems obtained with delta-alumina support were always higher than for the classical gamma-alumina. This support effect can be partially explained and supported by physicochemical characterization results of XPS and IR of adsorbed CO at low temperature (77 K). (c) 2012 Elsevier Inc. All rights reserved

From Si nanowire to SiC nanotube

International audienceSi nanowires (NWs), with diameters of about 800 nm and lengths of about 10 lm, previously synthesized by the VLS method with gold catalyst, were carburized at 1,100 C under methane for conversion into SiC nanostructures. These experiments have shown that Si NWs have been transformed into SiC nanotubes (NTs) with approximately the same sizes. Nanotubes’ sidewall thickness varies from 20 to 150 nm depending on the NTs’ height. These SiC nanotubes are hexagonal in shape and polycrystalline. A model of growth based on the outdiffusion of Si through the SiC layer was proposed toexplain the transformation from Si nanowires to SiC nanotubes. This model was completed with thermodynamic calculations on the Si–H2–CH4–O2 system and with results from complementary experiment using propane precursor. Routes for obtaining crystalline SiC NTs using this reaction are proposed