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We present a robust and versatile approach for the reproducible and controllable growth of single-walled carbon nanotubes (SWNTs) through a self-assembled mono-layer (SAM) technique coupled with an atomic hydrogen (Hat) pretreatment to control the catalytic metallic nanoparticles size and density. The nanoparticles are obtained from a self-assembled monolayer of metal complexes or salts on a SiO2 substrate using a two-step strategy. The oxide is first functionalized by silanization with a coordinating ligand leading to the formation of an anchoring SAM on the substrate. Then, metallic complexes such as ruthenium porphyrin (RuTPP) or metallic salts (FeCl3, RuCl3) are assembled by coordination bonds on the preformed organic SAM. Pyrolysis under radical hydrogen atmosphere of the as-prepared SAM yields metallic nanoparticles whose size and density are controlled and tuned. Using the as-formed nanoparticles as catalysts, SWNTs are grown by double hot-filament-assisted chemical vapor deposition (d-HFCVD). They exhibit a remarkably good crystalline quality, with a diameter (and type) strongly dependent on the nature of the initial catalyst precursor and its preparation. Field-effect transistors (FETs) with excellent characteristics were obtained using such in-place grown SWNTs. The electronic properties of the SWNTs can be tuned: the transistors obtained from Ru(TPP) and FeCl3 exhibit ION/IOFF current ratio up to ∼109, indicative of the direct growth of a high proportion of semiconducting nanotubes over than 98%. Such elevated values have been reported essentially for CNT-FETs devices based on individual semiconducting SWNTs. By contrast, devices obtained from the RuCl3 salt display ION/IOFF current ratio well below 102, indicating the direct growth of SWNTs highly enriched in metallic specimens.

International audience; Y- and comb-type carbon nanotrees formed from branched carbon nanofibres grown by plasma-enhanced chemical vapour deposition were studied by transmission electron microscopy. Different growth mechanisms are proposed for the two types of nanotrees based on the observed and reconstituted dynamic transformations of the catalyst particles during synthesis. However, the splitting of the larger catalyst particles is required for both kinds of nanotrees, whatever the involved growth mechanism. The carbon nanotrees are well crystallized and connections of the branches are continuous, which may be interesting for future applications in nanoelectronic devices and also composite materials.

Resume : Dans le contexte des ecrans plats a cristal liquide, on presente dans cet article une analyse detaillee du mecanisme de cristallisation du silicium amorphe par laser a excimeres. On montre en particulier que pour certaines conditions d'irradiation, les couches de silicium polycristallin obtenues permettent de fabriquer des transistors MOS presentant des mobilites n et p (respectivement de 350 et 150 cnvTVs) comparables a celles obtenues avec du materiau monocristallin sur isolant.

This contribution deals with the fabrication of electrode and supercapacitor cell using a new dynamic air-brush deposition technique. This method allows to achieve extremely (ou highly) uniform mats with finely tuned thickness and weight in a completely reproducible way. Using this deposition technique, we have analyzed the effect of mixture of CNTs and graphene/graphite on the electrode and cell properties (energy, power and capacitance). using a mixture of 75% of graphene/graphite and 25% of CNTs we increased the power by a factor 2.5 compared to bare CNTs based electrodes. We also analyzed the effect of the weight firstly on the capacitance and specific energy and then on the specific power. We were able to reach a specific power of 200kW/Kg and a specific energy of 9.1Wh/Kg with an electrode having a surface of 2cm 2 and a weight of 0.25mg composed by 50% of CNTs and graphene/graphite (using a common aqueous electrolyte). using our deposition technique we are able to achieve supercapacitors with ad-hoc characteristics simply modulating the weight and the concentration of the mixture in a completely reproducible way.

We present a systematic study of grain size and carrier mobility behaviour in polycrystalline graphene films grown on copper substrates with various surface roughness values. We first observe that as the surface roughness of the substrate decreases, the graphene grain size increases significantly, thus decreasing the density of grain boundaries. Then, using field-effect transistor structures, we confirm that as the substrate roughness decreases, carrier mobility values in graphene increase, whatever the channel length of the transistor. For a substrate rms roughness around 5 nm (measured on a 10 × 10 µm2 field) and using a fast growth process (~40 min), we obtain mobility values as high as ~6900 cm2 Vs−1 for electrons and ~6000 cm2 Vs−1 for holes in polycrystalline graphene with a small grain size of ~12–14 µm.

International audience; Isoprenoids constitute one of the largest families of natural compounds. They play essential functions in plant growth and development and furnish compounds of high interest for humans. Here, we present the current knowledge on isoprenoid metabolism before describing the strategies that have been used for isoprenoid metabolic engineering. We discuss the advantages and drawbacks of using microorganisms and plants as cell platform for the production of isoprenoids of interest.

The nucleation and growth of multiwall carbon nanotubes (MWCNTs) at the surface of crystalline iron-based catalysts are studied by in situ annealing and high-resolution transmission electron microscopy. Graphene planes, parallel to the catalyst surface, appear by a mechanism of step flow, where the atomic layers of catalyst are "replaced" by graphene layers. More interestingly, as the catalyst particles have curved or poly-faceted surfaces, those catalyst atomic layers correspond to no definite atomic plane. The step height may thus vary along a given step flow process. Step bunching due to impeded step migration, in certain growth conditions, yields characteristic catalyst nail-head shapes. Mastering this mechanism opens up the way to tailor the structure of MWCNTs, e.g. with highly parallel carbon walls.

Rapport sur Le blanchissement des coraux à la Réunion en 2009. Rapport ARVAM/PARETO/Université de la Réunion/MNHN pour le compte du GIP Réserve naturelle marine de la Réunion

As is well known, the application of gate-voltage stresses in conjunction with high source-drain voltages, V ds , modifies the electrical characteristics of polycrystalline silicon thin film transistors. In particular negative gate-voltage stresses on n-channel devices usually reduce both the leakage current and the transconductance. In this paper a complete analysis of hot carrier effects induced by different gate-bias stresses at high V ds is presented and discussed in terms of trap and interface state creation. It is shown that in certain stress regimes the leakage current can be reduced without the accompanying transconductance degradation.

Des couches de silicium amorphe de haute purete ont ete realisees dans un reacteur de type LPCVD (Low Pressure Chemical Vapour Deposition) dans des conditions ultra-pures a partir des gaz silane et disilane. L'evolution de la densite de germes par unite de surface est suivie a 580°C par microscopie electronique en cours de cristallisation en phase solide, ce qui permet d'en deduire la vitesse de germination a cette temperature. D'autre part, la variation de la taille des grains, sur les couches completement cristallisees, est etudiee par microscopie electronique a transmission (MET) en fonction de la temperature de recuit La fraction volumique cristallisee des films amorphes en cours de recuits isothermes est suivie par des mesures de conductance electrique in situ. Par combinaison de ces deux methodes de caracterisation nous pouvons remonter avec precision aux parametres thermodynamiques de la cristallisation concernant les deux types de depot.

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.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; The SlPPC2 phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) gene from tomato (Solanum lycopersicum) is differentially and specifically expressed in expanding tissues of developing tomato fruit. We recently showed that a 1966 bp DNA fragment located upstream of the ATG codon of the SlPPC2 gene (GenBank AJ313434) confers appropriate fruit-specificity in transgenic tomato. In this study, we further investigated the regulation of the SlPPC2 promoter gene by analysing the SlPPC2 cis-regulating region fused to either the firefly luciferase (LUC) or the beta-glucuronidase (GUS) reporter gene, using stable genetic transformation and biolistic transient expression assays in the fruit. Biolistic analyses of 5' SlPPC2 promoter deletions fused to LUC in fruits at the 8th day after anthesis revealed that positive regulatory regions are mostly located in the distal region of the promoter. In addition, a 5' UTR leader intron present in the 1966 bp fragment contributes to the proper temporal regulation of LUC activity during fruit development. Interestingly, the SlPPC2 promoter responds to hormones (ethylene) and metabolites (sugars) regulating fruit growth and metabolism. When tested by transient expression assays, the chimeric promoter: LUC fusion constructs allowed gene expression in both fruit and leaf, suggesting that integration into the chromatin is required for fruit-specificity. These results clearly demonstrate that SlPPC2 gene is under tight transcriptional regulation in the developing fruit and that its promoter can be employed to drive transgene expression specifically during the cell expansion stage of tomato fruit. Taken together, the SlPPC2 promoter offers great potential as a candidate for driving transgene expression specifically in developing tomato fruit from various tomato cultivars.

Since chemical vapor deposition of carbon-containing precursors onto transition metals tends to develop as the preferred growth process for the mass production of graphene films, the deep understanding of its mechanism becomes mandatory. In the case of nickel, which represents an economically viable catalytic substrate, the solubility of carbon is significant enough so that the growth mechanism proceeds in at least two steps: the dissolution of carbon in the metal followed by the precipitation of graphene at the surface. In this work, we use ion implantation to dissolve calibrated amounts of carbon in nickel thin films and grow graphene films by annealing. Observations of those graphene films using transmission electron microscopy , directly on the growth substrate as well as transfered on TEM grids, allowed us to precisely study the mechanisms that lead to their formation.

Here we present our on-going efforts toward the development of stable ballasted carbon nanotube-based field emitters employing hydrothermally synthesized zinc oxide nanowires and thin film silicon-on-insulator substrates. The semiconducting channel in each controllably limits the emission current thereby preventing detrimental burn-out of individual emitters that occurs due to unavoidable statistical variability in emitter characteristics, particularly in their length. Fabrication details and emitter characterization are discussed in addition to their field emission performance. The development of a beam steerable triode electron emitter formed from hexagonal carbon nanotube arrays with central focusing nanotube electrodes, is also described. Numerical ab-initio simulations are presented to account for the empirical emission characteristics. Our engineered ballasted emitters have shown some of the lowest reported lifetime variations (< 0.7%) with on-times of < 1 ms, making them ideally-suited for next-generation displays, environmental lighting and portable x-rays sources.

Field electron emission behavior of individual multiwalled carbon nanotubes (MWNTs), that are elements of a vertically aligned array grown on a Si wafer, were analyzed with a scanning anode field emission microscope. The electron emission of each MWNT followed the conventional Fowler–Nordheim field emission mechanism after their apexes were freed from the erratic adsorption species using a conditioning process at room temperature. The conditioning process led to stable emission currents and reduced their variations ΔI/I to less than 30% between different MWNTs of the array. This opens the possibility for using MWNTs in an array as independent electron sources for massively parallel microguns.

We compare the field emission characteristics of dense (109 nanofibers/cm2), sparse (107 nanofibers/cm2), and patterned arrays (106 nanofibers/cm2) of vertically aligned carbon nanofibers on silicon substrates. The carbon nanofibers were prepared using plasma-enhanced chemical vapor deposition of acetylene and ammonia gases in the presence of a nickel catalyst. We demonstrate how the density of carbon nanofibers can be varied by reducing the deposition yield through nickel interaction with a diffusion layer or by direct lithographic patterning of the nickel catalyst to precisely position each nanofiber. The patterned array of individual vertically aligned nanofibers had the most desirable field emission characteristics, highest apparent field enhancement factor, and emission site density.

International audience; Iron is a widely used catalyst for the growth of carbon nanotubes (CNTs) or carbon nanofibers (CNFs) by catalytic chemical vapor deposition. However, both Fe and Fe−C compounds (generally, Fe3C) have been found to catalyze the growth of CNTs/CNFs, and a comparison study of their respective catalytic activities is still missing. Furthermore, the control of the crystal structure of iron-based catalysts, that is α-Fe or Fe3C, is still a challenge, which not only obscures our understanding of the growth mechanisms of CNTs/CNFs, but also complicates subsequent procedures, such as the removal of catalysts for better industrial applications. Here, we show a partial control of the phase of iron catalysts (α-Fe or Fe3C), obtained by varying the growth temperatures during the synthesis of carbon-based nanofibers/nanotubes in a plasma-enhanced chemical vapor deposition reactor. We also show that the structure of CNFs originating from Fe3C is bamboo-type, while that of CNFs originating from Fe is not. Moreover, we directly compare the growth rates of carbon-based nanofibers/nanotubes during the same experiments and find that CNFs/ CNTs grown by α-Fe nanoparticles are longer than CNFs grown from Fe3C nanoparticles. The influence of the type of catalyst on the growth of CNFs is analyzed and the corresponding possible growth mechanisms, based on the different phases of the catalysts, are discussed.

Persistent photoconductance, a prolonged light-induced conducting behavior that lasts several hundred seconds, has been observed in semiconductors. Here we report persistent negative photoconductance and consecutive prominent persistent positive photoconductance in graphene. Unusually large yields of negative PC (34%) and positive PC (1652%) and remarkably long negative transient response time (several hours) were observed. Such high yields were reduced in multilayer graphene and were quenched under vacuum conditions. Two-dimensional metallic graphene strongly interacts with environment and/or substrate, causing this phenomenon, which is markedly different from that in three-dimensional semiconductors and nanoparticles.

We report that highly crystalline graphene can be obtained from well-controlled surface morphology of the copper substrate. Flat copper surface was prepared by using a chemical mechanical polishing method. At early growth stage, the density of graphene nucleation seeds from polished Cu film was much lower and the domain sizes of graphene flakes were larger than those from unpolished Cu film. At later growth stage, these domains were stitched together to form monolayer graphene, where the orientation of each domain crystal was unexpectedly not much different from each other. We also found that grain boundaries and intentionally formed scratched area play an important role for nucleation seeds. Although the best monolayer graphene was grown from polished Cu with a low sheet resistance of 260 Ω/sq, a small portion of multilayers were also formed near the impurity particles or locally protruded parts.

This paper describes a novel photocathode which is an array of vertically aligned multi-walled carbon nanotubes (MWCNTs), each MWCNT being associated with one p-i-n photodiode. Unlike conventional photocathodes, the functions of photon-electron conversion and subsequent electron emission are physically separated. Photon-electron conversion is achieved with p-i-n photodiodes and the electron emission occurs from the MWCNTs. The current modulation is highly efficient as it uses an optically controlled reconfiguration of the electric field at the MWCNT locations. Such devices are compatible with high frequency and very large bandwidth operation and could lead to their application in compact, light and efficient microwave amplifiers for satellite telecommunication. To demonstrate this new photocathode concept, we have fabricated the first carbon nanotube based photocathode using silicon p-i-n photodiodes and MWCNT bunches. Using a green laser, this photocathode delivers 0.5 mA with an internal quantum efficiency of 10% and an I(ON)/I(OFF) ratio of 30.

International audience; Confined lateral alumina templates are fabricated with different pore sizes by changing the acid electrolyte and the anodization voltage. The control of the number of pore rows down to one dimension is also achieved, by controlling the thickness of the starting aluminum film as well as the anodization voltage. We observe that the mechanism of pore formation in the lateral regime is very similar to that in the classical vertical situation.

We present a fully elaborated process to grow arrays of metallic nanowires with controlled geometry and density, based on electrochemical filling of nanopores in track-etched templates. Nanowire growth is performed at room temperature, atmospheric pressure and is compatible with low cost fabrication and large surfaces. This technique offers an excellent control of the orientation, shape and nanowires density. It is applied to fabricate field emission arrays with a good control of the emission site density. We have prepared Co, Ni, Cu and Rh nanowires with a height of 3 mu m, a diameter of 80 nm and a density of similar to 10(7) cm(-2). The electron field emission measurements and total energy distributions show that the as-grown nanowires exhibit a complex behaviour, first with emission activation under high field, followed by unstable emission. A model taking into account the effect of an oxide layer covering the nanowire surface is developed to explain this particular field emission behaviour. Finally, we present an in situ cleaning procedure by ion bombardment that collectively removes this oxide layer, leading to a stable and reproducible emission behaviour. After treatment, the emission current density is similar to 1 mA cm(-2) for a 30 V mu m-1 applied electric field.

Although carbon nanotubes have been actively studied for electronics applications during the past 2 decades (1), transistors made with those materials are still plagued by a number of problems, such as contact reproducibility, large hysteresis in the transfer characteristics as well as low on-current and large off-current values, to name a few. Single walled carbon nanotubes (SWNTs) were first considered as potential candidates for the replacement of Si MOS type transistors in VLSI circuits. However the main field of application of SWNTs is shifting towards large area electronics on flexible, plastic-type substrates (2, 3), a domain which is at present, less demanding in terms of device dimensions and integration density. In particular, random networks of SWNTs, which can be obtained by solution-processing or grown at low temperature by plasma enhanced chemical vapour deposition (PECVD), represent an attractive and viable option for the fabrication of electronic devices and circuits on non-refractory substrates (4). Also, since carrier injection in carbon nanotube field effect transistors (CNTFETs) is controlled by Schottky barriers at the nanotube/metal contacts, CNTFETs can be used for gas sensing applications (5). This is a consequence of poor “wetting” of most metals on the surface of SWNTs, thus allowing gas molecule to diffuse at the interface and modify the alignment of Fermi levels by introducing surface dipoles. Finally, SWNT random arrays will probably find applications in transparent conducting films (TCFs), see ref. 6, replacing some of the oxide-based films, particularly those incorporating indium, an element whose availability on earth is limited.

10 pages; International audience; Carbon nanofibres (CNFs) obtained by plasma enhanced chemical vapour deposition are made of cone-shaped graphene layers, the opening angle of which has a significant influence on their properties: the smaller the angle, the closer the properties to those of carbon nanotubes. That angle is determined by the shape of the metal nanoparticle used to catalyse the growth. We show in this paper that the shape of Ni nanoparticle catalysts, and in turn the CNF properties, can be tuned during plasma-enhanced chemical vapour deposition, by the choice of the etchant gas. We show in particular that a water-containing etchant (H2O or H2O+H2) increases the growth rate by an order of magnitude at 600°C compared to an ammonia-containing etchant (NH3 or NH3+H2), and leaves more elongated Ni particles with a cone angle three times smaller. We conclude that the cone angle and the growth rate are directly related, and propose a mechanism to explain that large difference between the two etchants.

International audience; Lateral porous anodic alumina (PAA) templates were used to organize carbon nanotubes (CNTs) grown by a hot-filament assisted chemical vapor deposition (HFCVD) process. For the CNT growth, we used a modified "home-made" HFCVD system with two independently powered filaments which are fitted respectively on the methane (CH4) gas line, which serves as a carbon precursor and on the hydrogen (H2) gas line, which acts as an etching agent for the parasitic amorphous carbon. Various activation powers of the hot filaments were used to directly or indirectly decompose the gas mixtures at relatively low substrate temperatures. A parametric study of the HFCVD process has been carried out for optimizing the confined CNTs growth inside the lateral PAA templates.

International audience; The synthesis of few-layered graphene is performed by ion implantation of carbon species in thin nickel films, followed by high temperature annealing and quenching. Although ion implantation enables a precise control of the carbon content and of the uniformity of the in-plane carbon concentration in the Ni films before annealing, we observe thickness non-uniformities in the synthesized graphene layers after high temperature annealing. These non-uniformities are probably induced by the heterogeneous distribution/topography of the graphene nucleation sites on the Ni surface. Taken altogether, our results indicate that the number of graphene layers on top of Ni films is controlled by the nucleation process on the Ni surface rather than by the carbon content in the Ni film.

International audience; Growth on transition metal substrates is becoming a method of choice to prepare large-area graphene foils. In the case of nickel, where carbon has a significant solubility, such a growth process includes at least two elementary steps: (1) carbon dissolution into the metal, and (2) graphene precipitation at the surface. Here, we dissolve calibrated amounts of carbon in nickel films, using carbon ion implantation, and annealing at 725 °C or 900 °C. We then use transmission electron microscopy to analyse the precipitation process in detail: the latter appears to imply carbon diffusion over large distances and at least two distinct microscopic mechanisms.

In order to utilize the unique properties of carbon nanotubes in microelectronic devices, it is necessary to develop a technology which enables high yield, uniform, and preferential growth of perfectly aligned nanotubes. We demonstrate such a technology by using plasma-enhanced chemical-vapor deposition (PECVD) of carbon nanotubes. By patterning the nickel catalyst, we have deposited uniform arrays of nanotubes and single free-standing aligned nanotubes at precise locations. In the PECVD process, however, detrimental amorphous carbon (a-C) is also deposited over regions of the substrate surface where the catalyst is absent. Here, we show, using depth-resolved Auger electron spectroscopy, that by employing a suitable deposition (acetylene, C2H2) to etching (ammonia, NH3) gas ratio, it is possible to obtain nanotube growth without the presence of a-C on the substrate surface.

5-Formyltetrahydrofolate (5-CHO-THF) is formed by a side reaction of serine hydroxymethyltransferase. Unlike other folates, it is not a one-carbon donor but a potent inhibitor of folate enzymes and must therefore be metabolized. Only 5-CHO-THF cycloligase (5-FCL) is generally considered to do this. However, comparative genomic analysis indicated (i) that certain prokaryotes lack 5-FCL, implying that they have an alternative 5-CHO-THF-metabolizing enzyme, and (ii) that the histidine breakdown enzyme glutamate formiminotransferase (FT) might moonlight in this role. A functional complementation assay for 5-CHO-THF metabolism was developed in Escherichia coli, based on deleting the gene encoding 5-FCL (ygfA). The deletion mutant accumulated 5-CHO-THF and, with glycine as sole nitrogen source, showed a growth defect; both phenotypes were complemented by bacterial or archaeal genes encoding FT. Furthermore, utilization of supplied 5-CHO-THF by Streptococcus pyogenes was shown to require expression of the native FT. Recombinant bacterial and archaeal FTs catalyzed formyl transfer from 5-CHO-THF to glutamate, with k(cat) values of 0.1-1.2 min(-1) and K(m) values for 5-CHO-THF and glutamate of 0.4-5 μM and 0.03-1 mM, respectively. Although the formyltransferase activities of these proteins were far lower than their formiminotransferase activities, the K(m) values for both substrates relative to their intracellular levels in prokaryotes are consistent with significant in vivo flux through the formyltransferase reaction. Collectively, these data indicate that FTs functionally replace 5-FCL in certain prokaryotes.

In this work, we will present a novel graphene synthesis technique, based on the ion implantation of carbon ions into polycrystalline transition metal thin films. Ion implantation is now a routine process developed by the semiconductor industry over the past three decades. It is used to dope the source and drain contact regions as well as to adjust the channel characteristics of CMOS transistors. One of the advantages of ion implantation is that it allows one to precisely control the carbon dose introduced in a particular substrate.

Le tome 2 de l‘étude de « définition des réseaux de surveillance de la qualité des masses d’eau côtières de l’île de Mayotte », présente sous forme cartographique les données bancarisées sous format MapInfo. Seules les études intéressantes vis à vis de la DCE et disponibles ont été référencées et prises en compte dans cet exercice (cf. références bibliographique du tome 2). Ce premier exercice de bancarisation, ne se veut pas exhaustif, et devra faire l’objet d’entretiens, d’ajouts réguliers.

We successfully synthesized organized Carbon nanotubes (CNTs) and Silicon Nanowires (SiNWs) arrays using LPAA. This approach can yield very dense assemblies of nano-objects with a planar-type organization compatible with existing tools inherited from advanced microelectronic processes and adapted to electronic devices as field effect transistors, interconnects, sensors, etc. CNTs/SiNWs were grown using Hot-filament Chemical Vapor Deposition (HFCVD) within lateral-type porous anodic alumina. We demonstrate that the pulsed electrodeposition of metal nanoparticles to be further used as catalysts inside the membranes requires specific thinning and pore widening process to remove the alumina barrier layer located at the bottom of the pores. The growth of CNTs was found to strongly depend on the electrodeposition conditions as well as on the CVD parameters. In addition, we found that introducing atomic hydrogen (generated using a hot-wire) as etching agent was essential to prevent parasitic carbon/silicon deposition on the surface of PAA or on the wall of pores and to improve CNTs/NWs growth. Such organized CNTs/SiNWs arrays are very promising as advanced microelectronic devices and their potentiality for photosensing applications were investigated.

Graphene has been given great attention to overcome current physical limits in electronic devices and its synthesis routes are developing rapidly. However, graphene film manufacturing is still hindered by either low throughput or low material quality. Here, we present a low temperature PE-CVD assisted graphene growth process on nickel thin films deposited on silicon oxide. Furthermore, our process leads to the formation of two separated graphene films, one at the nickel surface and the other at the Ni/SiO2 interface. A mixture of methane and hydrogen was employed as carbon precursor and activated by DC plasma. We found that the number of graphene layers on top of nickel can be controlled by carbon exposure time, from 1 to around 10 layers. Further annealing process of samples allowed us to achieve improved graphene films by the dissolution and segregation-crystallization process.

In this paper we demonstrate the efficiency of porous anodic alumina (PAA) to confine the growth of silicon nanowires (SiNWs). High-density arrays of parallel, straight and organized SiNWs have been realized, by Hot Wire Chemical Vapor Deposition (HW-CVD) growth process inside PAA templates with electrodeposited copper as catalyst. The PAA was made by the anodization of an aluminium layer, followed by the catalysts electrodeposition at the bottom of the pores. Subsequently, SiNWs were grown in a modified HW-CVD reactor with SiH 4 as the precursor gas. The morphology and the structure of the wires have been investigated by SEM and TEM, and their collective electrical behavior has been characterized with a 2-probes device.

The aim of this paper is to review our recent results on the growth and optimization of carbon nanotubes (CNTs) and CNT/Zinc Oxide nanostructures and present and discuss their suitability for various applications such as cold cathode electron sources for use in x-ray sources and lighting.

Graphene is perhaps the most promising material ever discovered for microelectronics applications, but its preparation includes either high-temperature processing or film transfer, and sometimes both of them, which forbids for the moment its introduction into fabrication lines. In this communication we report a synthesis route involving exposure of nickel thin films deposited on silicon oxide to a mixture of methane and hydrogen activated by DC plasma at 450°C. In addition of the awaited graphene film formed at the surface of catalyst layer, we observed the formation of a second graphene film at the catalyst/silicon oxide interface. To our knowledge, no other team have yet reported graphene synthesis directly on a dielectric substrate at low temperature. With the idea of increasing the graphene structural quality, we studied the effect of additional post growth high temperature annealing. The films synthesized were characterized using Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).