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Les primo-intervenants de la santé en cas de situation d’urgence radiologique sont dotés de moyens de protection et de détection. La législation du travailleur, exposé aux rayonnements ionisants, impose des normes strictes d’exposition, quantifiée par la dose efficace, unité de mesure, exprimée en sieverts. Les moyens de détection, en cas de contamination radio-nucléaire, des établissements de santé nécessitent une harmonisation des dotations et des valeurs seuils. Les formations des agents de la santé, en cas de situation d’urgence radiologique, est réalisé par les annexes 7, 8 et 9 de l’attestation de formation spécialisée aux gestes et soins d’urgence en situation sanitaire exceptionnelle (AFGSU spécialisée SSE).

Graphene sheets (mono- and multilayers) were synthesized by chemical vapor deposition and functionalized with various aromatic molecules such as Fe-/Co-porphyrin and Fe-phthalocyanine through π–π interactions. The resulting nanohybrid materials were characterized by Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM) techniques. The presence of physi-adsorbed molecules (Fe-/Co-porphyrin and Fe-phthalocyanine) on the graphene sheet surface is evidenced by spectroscopic and microscopic analyses, which confirm that these molecules are immobilized through electrostatic and π–π interactions. RS confirmed the n- or p-type doping of graphene, according to the chemical nature of those physi-adsorbed molecules. The electrical characteristics of electrolyte-gated graphene field-effect transistors (GFETs) based on nanohybrid materials were subsequently evaluated and demonstrated a charge transfer between the physi-adsorbed molecules and the graphene. All of these results suggest that the electronic structure of graphene can be tailored by doping with aromatic molecules. Density functional theory (DFT) calculations were performed to confirm these observations.

Solar cells built with arrays of semiconductor wires have been studied for several years. They present some potential advantages over their bulk counterparts, such as (much) less use of semiconductor material, as well as improved light absorption properties. Most wire-based solar cells are fabricated with arrays of semiconductor p–n junctions, either radial or axial. Here, using a newly developed random connection process based on nickel silicide nanowires, we have built Schottky-type solar cells on interdigitated base and emitter coplanar electrodes that reach an efficiency of 6.5% when only 64% of the footprint area of the device is covered with p-type Si wire light-absorbers. To the best of our knowledge, this is the best efficiency reported so far for a Schottky-type wire-based solar cell; a simple extrapolation of the surface area suggests that an efficiency of more than 10% can be reached, which is comparable to that of single-junction hydrogenated amorphous Si cells. We also compare the Schottky-type cell with a “control” p–i–n one using the same device layout and the same nickel silicide nanowire random connection process: the efficiency of the p–i–n cell is higher (∼8%) but this is due to a higher VOC, the short-circuit current density (ISC) being very similar in both cases, close to 20 mA/cm2. The maximum temperature reached throughout the fabrication process of the cells (whether Schottky-type or p–i–n) is 550 °C, corresponding to the growth of the crystalline Si wires. Altogether, the results presented here hold promises toward cheap photovoltaics based on the use of randomly organized and randomly connected Si wire arrays.

La décontamination d’urgence pour le risque chimique a pour but de réduire le plus précocement avant la décontamination approfondie les effets de la contamination et de l’intoxication de l’agent toxique tant sur les victimes que sur les primo-intervenants.

Fast charging rate and large energy storage are becoming key elements for the development of next-generation batteries, targeting high-performance electric vehicles. Developing electrodes with high volumetric and gravimetric capacity that could be operated at a high rate is the most challenging part of this process. Using silicon as the anode material, which exhibits the highest theoretical capacity as a lithium-ion battery anode, we report a binder-free electrode that interconnects carbon-sheathed porous silicon nanowires into a coral-like network and shows fast charging performance coupled to high energy and power densities when integrated into a full cell with a high areal capacity loading. The combination of interconnected nanowires, porous structure, and a highly conformal carbon coating in a single system strongly promotes the reaction kinetics of the electrode. This leads to fast-charging capability while maintaining the integrity of the electrode without structural collapse and, thus, stable cycling performance without using binder and conductive additives. Specifically, this anode shows high specific capacities (over 1200 mAh g–1) at an ultrahigh charging rate of 7 C over 500 charge–discharge cycles. When coupled with a commercial LiCoO2or LiFePO4cathode in a full cell, it delivers a volumetric energy density of 1621 Wh L–1with a LiCoO2cathode and a power density of 7762 W L–1with a LiFePO4cathode.

We present a detailed study on graphene-coated aluminum thin films for Li-ion battery anode applications. The best electrode ageing behavior is obtained for Al films encapsulated with four porous graphene layers. Graphene encapsulation prevents “crushed” Al nanoparticles from detaching from the anode, thus allowing prolonged charge–discharge cycling. Graphene also provides surface conduction paths for electrons as well as diffusion paths for Li atoms. For the first time, we report the electrochemical room temperature formation of phases such as Li3Al2and even Li9Al4, with a higher Li content than β-LiAl. More interestingly, we observe a progressive change of the composite thin film electrode, switching from a pure galvanic to a pseudocapacitive behavior as the size of the Al grains decreases from ∼100 to 5–10 nm due to repeated Li alloying-dealloying. The capacity values of ∼900 and 780 mAh/g are obtained after, respectively, 500 and 1000 charge–discharge cycles at 0.1C. Our results may refocus the interest of the battery community on Al-based thin film anodes, since they are potentially very simple to fabricate, particularly if porous graphene is replaced in the future by reduced graphite oxide.

We briefly introduce the main physical properties, as well as synthesis methods and device characteristics of novel two-dimensional (2D) materials such as transition metal dichalcogenides (TMDCs) and phosphorene. These 2D materials which can be real semiconductors (as opposed to graphene) offer new possibilities in terms of device properties/characteristics, particularly regarding the scaling down of the ever shrinking individual transistor. Their properties (forbidden gap, carrier mobility values) can be tailored by controlling their thickness and their dielectric environment. For TMDCs, alloying is another way of modifying intrinsic material's properties such as the band gap. Room temperature field-effect carrier mobility values as high as 700 cm2/Vs (electrons) and 5200 cm2/Vs (holes) have been measured for TMDCs and phosphorene respectively. Also, Ion/Ioff ratios over 108 have been reported for MoS2 transistors. Applications will soon emerge in the area of electronics, particularly flexible electronics as well as opto-electronics.

Single-doped (Ce3+,Tb3+), co-doped (Ce3+-Tb3+, Ce3+-Yb3+, Tb3+-Yb3+) and tri-doped (Ce3+-Tb3+-Yb3+) Y3Al5O12phosphors were synthesized by a solid-state reaction method. The XRD, excitation and emission spectra and the fluorescence lifetime of the samples were measured. The energy transfer mechanism was also investigated. The results showed that the energy transfer efficiency from Tb3+to Ce3+was 51% and the energy transfer efficiency from Ce3+to Yb3+was 63.1%. Concomitantly, both were more efficient than that from Ce3+to Tb3+(7%) and from Tb3+to Yb3+(10.2%). Also, the Yb3+ions received energy mainly from Ce3+ions in Ce3+-Tb3+-Yb3+tri-doped Y3Al5O12phosphors. Among these materials, Ce3+-Yb3+co-doped YAG phosphors are a better choice than others as a down-conversion material due to their higher energy transfer efficiency.

SiGe-On-Insulator layers are promising materials for high mobility pMOSFET channels and can be fabricated by the condensation technique. This technique is based on SiGe oxidation and a sound understanding of it is thus needed in order to fabricate optimized SGOI structures. The present study is a read-across of oxidation kinetics and Ge redistribution during dry Rapid Thermal Oxidation (RTO) of SiGe layers with different compositions and different oxidation temperatures. The evolution of the Ge concentration below the oxidation front is found to follow different regimes depending on the oxidation temperature. We examine them in light of a competition between oxidation rate and diffusion rate. It is also shown that RTO of SiGe is faster than Si and that the oxidation rate depends not only on the initial Ge concentration, but also on the oxidation temperature. A correlation between the Ge concentration below the oxidation front and oxidation kinetics is evidenced.

Metal oxide nanoparticles decorating graphene have attracted abundant interest in the scientific community owing to their significant application in various areas such as batteries, gas sensors, and photocatalysis. In addition, metal and metal oxide nanoparticles are of great interest for the etching of graphene, for example, to form nanoribbons, through gasification reactions. Hence it is important to have a good understanding of how nanoparticles interact with graphene. In this work we examine, in situ, the behavior of CuO and ZnO nanoparticles on graphene at room temperature while irradiated by electrons in a transmission electron microscope. ZnO is shown to etch graphene through gasification. In the gasification reaction C from graphene is released as CO or CO2. We show that the reaction can occur at room temperature. Moreover, CuO and ZnO particles trapped within a graphene fold are shown to effuse out of a fold through small ruptures. The mass transport in the effusion process between the CuO and ZnO particles is fundamentally different. Mass transport for CuO occurs in an amorphous phase, while for ZnO mass transport occurs through the short-lived gliding of vacancies and dislocations. The work highlights the potential and wealth of electron beam driven chemical reactions of nanomaterials, even at room temperature.

Des couches de silicium amorphe de haute pureté ont été réalisées dans un réacteur de type LPCVD (Low Pressure Chemical Vapour Deposition) dans des conditions ultra-pures à partir des gaz silane et disilane. L'évolution de la densité de germes par unité de surface est suivie à 580°C par microscopie électronique en cours de cristallisation en phase solide, ce qui permet d'en déduire la vitesse de germination à cette température. D'autre part, la variation de la taille des grains, sur les couches complètement cristallisées, est étudiée par microscopie électronique à transmission (MET) en fonction de la température de recuit. La fraction volumique cristallisée des films amorphes en cours de recuits isothermes est suivie par des mesures de conductance électrique in situ. Par combinaison de ces deux méthodes de caractérisation nous pouvons remonter avec précision aux paramètres thermodynamiques de la cristallisation concernant les deux types de dépôt.

Ge condensation using RTO is investigated to produce good quality SGOI channel. This study shows the significant role of the RTO temperature in Ge condensation. First, Ge diffusion requires a RTO temperature above 950degC to start homogenization of Ge in the channel. This is mandatory to minimize the risk of defects generation. Then, inconsistently to thermodynamics calculation, Ge-O bounds are formed during oxidation and a higher temperature oxidation leads to a lower Ge-O bounds formation. Therefore, Ge condensation using a 1100degC RTO is preferred. It is implemented in a SOI/SGOI co-integration to produce SGOI channel for PMOS transistor. Such channel exhibits a very smooth surface (RMS roughness below 0.15nm), a controlled Ge content (16%) and a high compressive strain (1%). Moreover, PMOS Vt modulation by the Ge concentration was performed with a sensitivity of 10mV/%. As a result, this study demonstrates that RTO is a solid alternative to furnace for Ge condensation.

This contribution deals with the fabrication of electrodes and supercapacitor cells using a new dynamic air-brush deposition technique. This method yields highly uniform mats with finely tuned thickness and weight in a completely reproducible way. Using this deposition technique, we analyze the effect of mixtures of CNTs and graphite on the electrode and cell properties (energy, power and capacitance) and observe that with a mixture of 75% of graphite and 25% of CNTs, we increase the power by a factor 2.5 compared to bare CNT-based electrodes. We also analyze the effect of the electrodes' weight first on the capacitance and specific energy and second on the specific power. We report a specific power of 200 kW/Kg and a specific energy of 9.1 Wh/Kg with electrodes having a surface of 2 cm2 and a weight of 0.25 mg composed by 50% of CNTs and graphite (using a common aqueous electrolyte). Our deposition technique delivers supercapacitors with ad-hoc characteristics, by simply modulating the weight and the concentration of the CNT/graphite mixture in a completely reproducible way and with an industrially suitable and low-cost method.

We present electronically controlled field emission characteristics of arrays of individually ballasted carbon nanotubes synthesized by plasma-enhanced chemical vapor deposition on silicon-on-insulator substrates. By adjusting the source–drain potential we have demonstrated the ability to controllable limit the emission current density by more than 1 order of magnitude. Dynamic control over both the turn-on electric field and field enhancement factor have been noted. A hot electron model is presented. The ballasted nanotubes are populated with hot electrons due to the highly crystalline Si channel and the high local electric field at the nanotube base. This positively shifts the Fermi level and results in a broad energy distribution about this mean, compared to the narrow spread, lower energy thermalized electron population in standard metallic emitters. The proposed vertically aligned carbon nanotube field-emitting electron source offers a viable platform for X-ray emitters and displays applications that require accurate and highly stable control over the emission characteristics.

In this paper, we briefly review the use of carbon nanotubes and semiconductor nanowires, which represent a new class of nanomaterials actively studied for thin film transistors and electronics applications. Although these nanomaterials are usually synthesised at moderate to high temperatures, they can be transferred to any kind of substrate after growth, paving the way for the fabrication of flexible displays and large area electronics systems on plastic. Over the past few years, the field has progressed well beyond the realisation of elementary devices, since active matrix displays driven by nanowire thin film transistors have been demonstrated, as well as the fabrication of medium scale integrated circuits based on random arrays of carbon nanotubes. Also, graphene, a new nanomaterial has appeared in the landscape; although it is a zero gap semiconductor, it can still be used to make transistors, provided narrow ribbons or bilayers are used. Graphene is also a serious contender for the replacement of oxide-based transparent conducting films.

We present some of our first experiments on the controlled growth of silicon nanowires and carbon nanotubes in lateral porous alumina templates synthesized by anodic oxidation of Al thin films. Under adapted chemical vapor deposition growth conditions, and using the vapor-solid-liquid mechanism, the pores of the lateral membranes can be partially filled with silicon nanowires or carbon nanotubes, yielding a composite thin film of parallel-organized nano-objects. Such composite thin films can be further tailored and shaped by classical microelectronic-type tools and processes, in order to fabricate electronic devices.

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The ability to grow carbon nanotubes/nanofibres (CNs) with a high degree of uniformity is desirable in many applications. In this paper, the structural uniformity of CNs produced by plasma enhanced chemical vapour deposition is evaluated for field emission applications. When single isolated CNs were deposited using this technology, the structures exhibited remarkable uniformity in terms of diameter and height (standard deviations were 4.1 and 6.3&percent; respectively of the average diameter and height). The lithographic conditions to achieve a high yield of single CNs are also discussed. Using the height and diameter uniformity statistics, we show that it is indeed possible to accurately predict the average field enhancement factor and the distribution of enhancement factors of the structures, which was confirmed by electrical emission measurements on individual CNs in an array.

We report on the fabrication of field emission microcathodes which use carbon nanotubes as the field emission source. The devices incorporated an integrated gate electrode in order to achieve truly low-voltage field emission. A single-mask, self-aligned technique was used to pattern the gate, insulator and catalyst for nanotube growth. Vertically-aligned carbon nanotubes were then grown inside the gated structure by plasma-enhanced chemical vapour deposition. Our self-aligned fabrication process ensured that the nanotubes were always centred with respect to the gate apertures (2 µm diameter) over the entire device. In order to obtain reproducible emission characteristics and to avoid degradation of the device, it was necessary to operate the gate in a pulsed voltage mode with a low duty cycle. The field emission device exhibited an initial turn-on voltage of 9 V. After the first measurements, the turn-on voltage shifted to 15 V, and a peak current density of 0.6 mA cm^-2 at 40 V was achieved, using a duty cycle of 0.5%.

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Polycrystalline silicon is a promising candidate for the fabrication of thin-film transistors used to control the pixel voltage of active-matrix liquid-crystal displays. Results are presented on the ultra-high vacuum chemical vapour deposition of silicon thin films and on the gate-oxide deposition at low temperature by distributed electron-cyclotron-resonance-plasma-enhanced chemical vapour deposition. It is shown that high electron mobilities and low off currents characterise the transistors fabricated with these techniques.

Polycrystalline silicon thin-film transistors (TFTs) have been fabricated by using a combined fast solid-phase crystallization (SPC) process followed by excimer laser annealing (ELA). The electrical characteristics of the devices, after post-hydrogenation, show average field effect mobilities > 100 cm2/Vs and better noise performance, if compared to conventional SPC-polysilicon TFTs. A main advantage of the presented technique is the reduced sensitivity of the device performances to the energy density used during ELA.

The defect structure of conformally grown Si films is investigated using electron microscopy techniques. Twins, stacking faults and dislocations are evidenced, mainly located at the different Si/SiO2interfaces. A qualitative model of defect generation is presented which suggests that these different defects mainly originate from differential thermal expansion problems associated to the "micro-roughness" of the Si/SiO2lateral interfaces.

Interface state creation, induced by hot hole injection, has been frequently observed in n-channel polysilicon thin-film transistors, when subjected to prolonged bias stress with negative gate biases. In this work we propose a new model for the kinetics of interface state formation, that closely links the interface state generation to the measured gate leakage current. The interface state generation mechanism appears to be driven by the recombination of hot holes (injected from the semiconductor active layer) with electrons (injected from the gate electrode). This model is shown to fit very well the time evolution of the interface states, as determined by the sheet conductance of the damaged region close to the drain.

The kinetics of crystallization of high-purity amorphous and mixed-phase silicon films obtained by pyrolysis of disilane gas in the millitorr pressure range were studied. A combination of in situelectrical conductance measurements and transmission electron microscopy analysis was used to determine the crystallization parameters. For mixed-phase films we report an activation energy for the nucleation rate of the order of 2.9 eV, compared to approximately 3.7 eV for the completely amorphous ones; the activation energy for the growth rate is roughly equal to 2.7 eV for the two types of films analyzed.