Abstract: This talk is intended to give an overview of research in Nanoscience and Nanotechnology (N&N) in France and especially at the French National Center for Scientific Research (CNRS), which has made research in N&N one of its five priorities. In the first part we list the main scientific issues at stake, as they were identified in a recent scientific workshop held at CNRS. In the second part we present the French organization of research in N&N and give comparative estimates of the funding in France, Europe, USA and Japan. We end up by summarizing some elements of CNRS strategy in the field.
Abstract: In order to mimic the behaviors of natural tissue, the optimal approach for designing novel biomaterials has to be inspired to nature guidelines. One of the major challenge consists in the development of well-organized structures or scaffolds with controlled porosity in terms of pore size, pore shape and interconnection degree able to guide new tissue formation during the in vivo degradation following the scaffold implantation. Scaffolds endowed with molecular cues together to a controlled degradation profile should contribute to cell proliferation and differentiation, controlled vascularization, promoting the remodeling of neo tissue through a gradual transmission of bio-chemicals and biophysical signals as performed by the extracellular matrix (ECM). Here, different polymers and composites have been investigated to design scaffolds with peculiar micro and/or nanometric morphological features in order to satisfy all these requirements: a) bioactive scaffolds, with tailored porosity and high pores interconnectivity were developed by integrating PLA fibres, Calcium Phosphates particles or Hyaff11 phases into a Poly(ε-caprolactone) (PCL) matrix by the combination of filament winding technology and phase inversion/salt leaching technique as mineralised ECM analogue for bone regeneration; b) custom made PCL/hydroxyapatite scaffolds were designed by imaging and rapid prototyping technologies for the osteochondral defect. c) Ester of Hyaluronic Acid reinforced with degradable fibres were processed by composite technology, phase inversion and salt leaching technique, to obtain scaffolds for meniscus regeneration. d) PCL and gelatin nanofibres were obtained by highly customized fibre deposition via electrospinning to guide the nerve outgrowth in nerve regeneration. All the proposed approaches offer the chance of realizing tailor-made platforms with micro/nanoscale architecture and chemical composition suitable for the regeneration of the extracellular matrix of a large variety of natural tissues (i.e, bone, menisci, osteochondral and peripheral nervous tissues).
Abstract: In this paper, the issues related to in-situ doping of silicon carbide (SiC) semiconductor during epitaxial growth are reviewed. Some of these issues can find solution by using an original approach called vapour-liquid-solid (VLS) mechanism. In this technique, the SiC seed is covered by a Sibased melt and is fed by propane in order to growth the epitaxial film. Using Al-Si melts and temperatures as low as 1100°C, very high p type doping was demonstrated, with a record value of 1.1021 at.cm-3. It leads to very low contact resistivity and even to metallic behaviour of the SiC deposit even at low temperature. Using Ge-Si melts, non intentionally low doped n type layers are grown. By forming Si-containing liquid droplets on a SiC seed, one can extrapolate this VLS growth to selective epitaxial growth (SEG). Such approach was successfully applied for both Al and Ge-based systems in order to form p+ and n doped areas respectively.
Abstract: Adhesives have been used in the footwear industry as an alternative to sewing or application of nails, staples or tacks to bond several parts of the shoes, the most critical bonding is the upper to sole bonding. However, as a limitation, the bonding with adhesives in shoe industry needs a severe control of all steps involved in the formation of the joints to avoid adhesion problems, mainly the separation of the sole from the upper.
Abstract: Nanoporous solids characterized by a narrow pore size distribution such as zeolites (aluminosilicates) and related materials (other silica-based materials, phosphate-based materials,...) have a large range of application. These solids and in particular the pure silica zeolites (named zeosils) which display a non-charged framework are very promising solids for the trapping of air pollutants (odors, VOCs,...) but also, thanks to their strong hydrophobic character, they can be used in the field of energetics. After some generalities on these solids, this latter application is illustrated by few examples.
Abstract: The use of nanostructured non-conventional semiconductors such as conjugated polymers and metal oxides (e.g. TiO2), opens promising perspectives towards a new generation of solar cells based on the concept of donor:acceptor bulk heterojunctions. In this concept donor material and acceptor material form interpenetrating networks allowing light absorption, charge transfer and charge transport throughout the entire bulk of the thin film. Since nanomorphology is of crucial importance for this type of solar cells, in this contribution the use of nanofibers in bulk heterojunction solar cells is explored in order to obtain highways for charge transport. We investigate in particular the use of P3AT (poly(3-alkylthiophene)) nanofibers and show that the polymer fraction aggregated into fibers can be easily controlled by temperature. We find an optimal efficiency at intermediate fiber fraction and show that it can be linked to the morphology of the active layer.
Abstract: In this work, the re-use of aluminum AA6061 chips and fly ash particles by solid-state processes (cryomilling, cold compaction and hot extrusion) is presented. The process was performed in following steps: comminuting of chips, cryomilling of comminuted chips, aluminum powders and fly ash particles, cold pressing-hot extrusion approach without sintering step. Comparative analysis of the recycled composites with fine and coarse granulated chips was focused on mechanical properties and correlated to microstructural features. The density and electrical conductivity of the recycled composites are lower than those of the unreinforced aluminum alloy due to the presence of fly ash particles. Regarding mechanical properties, the recycled composites with coarse granulated chips showed higher hardness and compressive strength than the recycled composites with fine granulated chips, but the compressive strength of the recycled composites with coarse granulated chips decreased with the increase of fly ash content.
Abstract: In this work we report on the structural and electrical properties of SiO2/Si3N4/HfO2 memory stacks with emphasis upon the influence of Atomic Layer Deposition chemistry used for forming the HfO2 blocking layer. Two HfO2 precursor chemistries were employed, the tetrakis- (ethylmethylamino)hafnium (TEMAH) and the bis(methylcyclopentadienyl)methoxymethylhafnium (HfD-04). Ozone was used as the oxygen source. The structural characteristics of the stacks were examined by means of TEM and GIXRD. Comparative studies conducted with the use of platinum gated capacitors showed that the samples grown using TEMAH have an increased electron trapping ability in comparison to the HfD-04 ones. While the two structures exhibit similar Write/Erase and retention characteristics, The samples grown from TEMAH can sustain more repeated W/E cycles (> 3×105 in the 10V/-11V, 10 ms regime) compared to the samples grown from HfD-04 (< 104 W/E cycles). This difference in endurance characteristics is attributed mainly to the different deposition temperatures used with these two precursors and the nature of the interfacial layer they produce between the Si3N4 and the HfO2 layers.
Abstract: Progress in semiconductor technologies have been so consequent these last years that theoretical limits of silicon, speci cally in the eld of high power, high voltage and high temperature have been achieved. At the same time, research on other semiconductors, and es- pecially wide bandgap semiconductors have allowed to fabricate various power devices reliable and performant enough to design high eciency level converters in order to match applications requirements. Among these wide bandgap materials, SiC is the most advanced from a techno- logical point of view: Schottky diodes are already commercially available since 2001, JFET and MOSFET will be versy soon. SiC-based switches Inverter eciency bene ts have been quite established. Considering GaN alternative technology, its driving force was mostly blue led for optical drive or lighting. Although the GaN developments mainly focused for the last decade on optoelectronics and radio frequency, their properties were recently explored to design devices suitable for high power and high eciency applications. As inferred from various studies, due to their superior material properties, diamond and GaN should be even better than SiC, silicon (or SOI) being already closed to its theoretical limits. Even if the diamond maturity is still far away from GaN and SiC, laboratory results are encouraging speci cally for very high voltage devices. Apart from packaging considerations, SiC, GaN and Diamond o ers a great margin of progress. The new power devices o er high voltage and low on-resistance that enable important reduction in energy consumption in nal applications. Applications for wide bandgap materials are the direction of high voltage but also high temperature. As for silicon technology, WBG-ICs are under development to take full bene ts of power and drive integration for high temperature applications.