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In order to reduce substrate costs and increase light absorption, solar cells based on semiconductor wire arrays are currently being actively studied. Whether built with Si, InP or other semiconductor materials, wire-based cells invariably use a transparent conductive coating for one of the electrodes, which complicates the processing and does not contribute to the reduction of the overall cost of the cell. Here, we propose a totally novel connection process, where the transparent conductive electrode is replaced with an array of in situ grown metallic nanowires. During their growth, these metallic nanowires randomly connect to core–shell p-i-n Si wires previously synthesized by chemical vapor deposition. We demonstrate the feasibility of this new random connection concept by using a coplanar solar cell design with interdigitated base and emitter contacts. We obtain a high fill factor of ~74% and efficiencies of 4.5% with only 33% of the surface covered by p-i-n Si wires.

The successful mechanical exfoliation and chemical synthesis of graphene has attracted considerable attention for the synthesis of other two-dimensional materials on graphene template. Chalcogenide materials such as Sb2Te3 are of interest due to the rhombohedral lattice structure with two-dimensional hexagonally closed-packed atomic layers along the c-axis. Here we synthesized c-axis-oriented Sb2Te3 nanoplates (NPs) on graphene substrates by the microwave-assisted solvothermal method. The microwave irradiation resulted in a higher temperature of graphene, compared with the synthesis solution, which was revealed by the single-mode microwave experiments and an analytical model based on energy balance and convective heat transfer. Besides, the lattice mismatch between c-axis-oriented Sb2Te3 and bridge sites of graphene was only 4%, which is also favorable for the graphene-templated Sb2Te3 synthesis. c-Axis-oriented single-crystalline Sb2Te3 NPs as large as 7 μm could be successfully synthesized on graphene w...

In this work, we present a practical approach for controlling single walled carbon nanotubes (SWCNTs) diameter distribution through thin film Ru catalyst, coupled with hydrogen pre-treatment. Uniform and stable Ru nanoclusters were obtained after dewetting the Ru thin films under atomic hydrogen pre-treatment. SWCNTs were synthetized by double hot filament chemical vapor deposition (d-HFCVD) on SiO2/Si substrates at different temperatures. We found that the temperature is an important synthesis parameter that in fluences the diameter distribution of the final SWCNTs. Statistical analysis of the Raman radial breathing modes evidences the growth of highly enriched semi-conducting SWCNTs (about 90%) with narrow diameter distribution that correlates directly with the catalyst particle size distribution. Electrical measurement results on as-grown SWCNTs show good thin-film transistor characteristics.

Kinking of semiconductor nanowires grown by the vapour–solid–liquid (VSL) mechanism has long been observed and studied, particularly for Si. A large variety of turning angles for kinked Si nanowires (KSiNWs) has been reported in the literature, but most authors have studied the kinking mechanism rather than the structure and corresponding geometrical features of the kinks. Here, we have investigated the relationship between the turning angles and the structure (down to atomic level) of KSiNWs grown by VSL from indium nanoparticles. By using transmission electron microscopy, we have characterized the transition regions between different segments of KSiNWs of various crystallographic orientations. We have found that most turning angles can be viewed as rich combinations of different types of {111} coherent twins that coexist within the transition regions between different segments of KSiNWs.

Targeting the integration of embedded non-volatile memories on thin-silicon body technology, high temperature oxide (HTO) is evaluated on a 40nm automotive eFlash process as replacement of furnace grown thick gate oxide for high voltage transistors. Different thermal treatments are evaluated to enhance HTO quality, including growth of interfacial layer, reoxidation and high temperature annealings. Transistor performance and reliability are thoroughly studied, showing that the main challenge for HTO integration is time-dependent dielectric breakdown. Because of higher charge trapping, HTO is found to be less reliable than grown oxide. However, optimized dedicated treatments successfully improve HTO quality and reliability.

The last 60 years have witnessed advanced technological innovation for disaster risk reduction (DRR) with the invention of high-resolution satellite imagery, digital cartography and modern engineering building techniques to high-yielding agricultural production. However, none have been highly satisfying in lessening the impact of disasters. The significant factor for the limited success of modern scientific society is that it views the world from a temporal perspective where humans are believed to be an active agent in modifying every natural possibility into opportunity. The very composite environmental system is simplified whilst extracting resources, resulting in resource depletion and environmental degradation, consequently opening the door for disaster. Technocratic science must recognise the need for a relational or holistic approach rather than believing in reductionist approaches alone whilst dealing with natural calamities. In this context, the knowledge of traditional societies is important to fill up the existing gaps created by the modern society. Traditional knowledge has different sets of ingredients to foster the development of the relational or holistic approach as it involves, interacts and interconnects humans, non-humans (animals and plants) and nature together, setting a perfect balance for sustainable development and DRR. It has vast undocumented observational data of changing natural phenomena, and in today’s scenario of climate change and uncertainty, it can create a path for reliable adaptation measures from climate-induced disasters. Thus, a holistic approach is needed for comprehensive DRR measures where both scientific and traditional knowledge systems can work together. The main purpose of this article was to explore the effective ingredients of traditional knowledge in DRR and how this age-old wisdom can be offered a hand to its integration into and collaboration with scientific research and management for DRR. To fulfil the objectives, a theoretical desk study approach was followed by identifying relevant studies, highlighting traditional knowledge in DRR from empirical and grey literatures, archive materials, biblical stories and so on. This research highlights some of the good practices of traditional knowledge in DRR and the possible path of collaboration of two knowledge systems in DRR.

We present a robust and versatile approach for the reproducible and controllable growth of single-walled carbon nanotubes (SWNTs) through a self-assembled monolayer (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 ...

High mobility channels are considered as an interesting path to increase PMOS performances for advanced CMOS technology. Silicon-Germanium On Insulator (SGOI) benefits from both the advantage of the SiGe material (hole mobility booster) and the On Insulator structure (better electrostatic control of the channel by the gate) [1]. The co-integration of NMOS and PMOS, respectively on Silicon On Insulator (SOI) and SGOI zones, can be enabled easily by the Ge condensation technique [1,2]. This technique is based on the competition between Ge diffusion and Si oxidation which are both driven by temperature. For this purpose, mainly furnace oxidation is reported in the literature [1-3]. In this work, we propose to study Ge condensation using Rapid Thermal Oxidation (RTO) as an alternative process. SGOI structures were fabricated on 300mm SOI wafers, with 11nm thick top silicon. First, epitaxy layers of SiGe were grown with varying thickness (from 3 to 10nm) and Ge concentration (from 10 to 40%). The SiGe film was grown by Rapid Thermal Chemical Vapor Deposition at temperature between 600°C and 650°C. Then, Ge condensation was performed by RTO in O2 ambient at temperatures between 950°C and 1150°C. Both aspects of Ge condensation were studied: Ge diffusion then Si oxidation. The RTO temperature effect on Ge diffusion was analysed by ToF-SIMS (Figure 1). In the case of short oxidation duration (below 2 minutes), as typically used in RTO compared to furnace (several hours), almost no diffusion is observed at 950°C. This leads to Ge enrichment of the initial SiGe layer with Ge concentration gradient. For longer oxidation, this might result in very high Ge concentration generating strain relaxation via stacking fault creation [4]. Therefore, temperatures above 950°C are prefered to avoid defects creation. TEM and STEM-EDX of the structure after condensation (Figure 2) shows that Ge concentration is still not totally homogeneous at 1100°C. Oxidation kinetics is shown on Figure 3, comparing the effect of substrate: SiGe/Si/BOX vs Si. SiGe is oxidized faster than Si, as already reported [5,6]. Moreover, SiGe oxidation is enhanced with increasing Ge concentration. Same trend is observed concerning SiGe thickness, indicating the effect of Ge diffusion in the underneath Si layer. A compositional analysis of the oxide grown by condensation was performed by XPS, monitoring the Ge3d peak (Figure 4). Starting from the same SiGe/Si/BOX structure, the oxide thickness was kept the same using different RTO temperatures but tuning the O2 pressure and the RTO duration. The effect of Ge diffusion is clearly observed by the intensity of the Ge-Si contribution. Higher temperature leads to lower Ge concentration due to a more homogeneous Ge distribution. Surprisingly, Ge-O bounds are also observed, whereas SixGe1-xalloy oxidation is thermodynamically considered to be Si selective [7]. Moreover, the amount of Ge-O bounds increases when the RTO temperature decreases. As shown previously, low temperature oxidation leads to high Ge concentration at the SiO2/SiGe interface, which may enable the formation of Ge-O bounds [8]. As a consequence, oxidation kinetics plays an important role in this phenomenon. This study reveals the significant role of temperature in Ge condensation by RTO. Due to kinetics effect, Ge-O bounds are formed which is not predicted by thermodynamics. Finally, the role of temperature will be investigated through electrical characterization of the SixGeyO properties. [1] B. Vincent at al, Mat. Sc. Semicond. Proc. 11, 2008 [2] T. Tezuka et al., Jpn. J. Appl. Phys. 40, 2886, 2001. [3] Z. Di et al., J. Crystal Growth 281, 2005 [4] B. Vincent, Appl. Phys. Lett. 90, 2007 [5] O. W. Holland et al., Appl. Phys. Lett. 51, 7, 1987 [6] S. J. Kilpatrick et al., J. Appl. Phys. 81, 12, 1997 [7] D. C. Paine et al, J. Appl. Phys. 70, 5076, 1991 [8] J. Eugene, Appl. Phys. Lett. 59, 78, 1991

Enhanced carrier–carrier interactions in hybrid nanostructures exhibit exceptional electronic and optoelectronic properties. Carbon nanotubes demonstrate excellent switching behavior with high on/off ratio and high mobility but do not show photoresponse in the visible range, whereas quantum dots (QDs) shows excellent optical response in various optical ranges which can be tuned with diameter. Here, a simple and effective way to develop hybrid phototransistors with extraordinary optoelectronic properties is presented by decorating semiconducting QDs on the surface of a single-walled carbon nanotube (SWCNT). This hybrid structure demonstrates clear negative photoresponse and optical switching behavior, which could be further tuned by applying external gate bias in the future. A clear type conversion of SWCNT transistor from p-type to n-type caused by a charge transfer from attached QDs to CNT is demonstrated. Moreover, this hybrid structure also demonstrates an enhancement in ‘optical Stark effect’ without applying any external electric field. Charged SWCNT surface plays a key role behind the enhancement of optical Stark effect in QDs. The carrier dynamics of the QD and CNT heterostructures system highlights the potential application opportunity of the quantum dot systems, which can be adaptable to the current technologies.

International audience; The fabrication of ultrathin compressively strained SiGe-On-Insulator layers by the condensation technique is likely a key milestone towards low-power and high performances FD-SOI logic devices. However, the SiGe condensation technique still requires challenges to be solved for an optimized use in an industrial environment. SiGe oxidation kinetics, upon which the condensation technique is founded, has still not reached a consensus in spite of various studies which gave insights into the matter. This paper aims to bridge the gaps between these studies by covering various oxidation processes relevant to today's technological needs with a new and quantitative analysis methodology. We thus address oxidation kinetics of SiGe with three Ge concentrations (0%, 10%, and 30%) by means of dry rapid thermal oxidation, in-situ steam generation oxidation, and dry furnace oxidation. Oxide thicknesses in the 50 angstrom to 150 angstrom range grown with oxidation temperatures between 850 and 1100 degrees C were targeted. The present work shows first that for all investigated processes, oxidation follows a parabolic regime even for thin oxides, which indicates a diffusion-limited oxidation regime. We also observe that, for all investigated processes, the SiGe oxidation rate is systematically higher than that of Si. The amplitude of the variation of oxidation kinetics of SiGe with respect to Si is found to be strongly dependent on the process type. Second, a new quantitative analysis methodology of oxidation kinetics is introduced. This methodology allows us to highlight the dependence of oxidation kinetics on the Ge concentration at the oxidation interface, which is modulated by the pile-up mechanism. Our results show that the oxidation rate increases with the Ge concentration at the oxidation interface. Published by AIP Publishing.

A method to form the plasmonic lattice mode of periodic metallic nanoparticle arrays is presented. In the arrays, each Ag nanosphere is on the top of a SiO2 nanopillar which sits on a quartz substrate. The simulated results show that, in the wavelength range around the period of the arrays, the plasmonic lattice mode can be formed. The transmittance of the structure varies rapidly from the maximum to the minimum in a narrow wavelength band. This is attributed to the wavelength-dependent diffracted waves generated by the periodic arrays and the weak near-field coupling between Ag nanospheres and the quartz substrates. Increasing the height of SiO2 nanopillars can weaken the near-field coupling between Ag nanospheres and the quartz substrates, and lead to the greater effects of the diffracted waves on the transmittance. As a result, the plasmonic lattice mode can be optimized. This method provides a possible way to promote the application of the plasmonic lattice mode.

67 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 cm 2 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. 8 9 10 11 12 13 14 15 16

The demand for higher speed and lower power consumption ICs has motivated research for higher mobility channel materials (1). Compressively strained SiGe is known to feature higher hole mobility than Si and is largely compatible with the Si CMOS manufacturing platform. Besides, the FDSOI transistor architecture allows power consumption reduction (2), thus making SiGe-On-Insulator (SGOI) channels promising. SGOI layers can be fabricated by the so-called condensation technique, which is based on concurrent Si selective thermal oxidation of SiGe and SiGe composition homogenization by Si and Ge interdiffusion (see Figure 1) (3). Therefore, a sound understanding of kinetics of oxidation and interdiffusion of SiGe is required to develop optimized SGOI structures. SiGe dry oxidation rate has been reported to be higher (4) than or equal (5)(6) to the one of Si. It therefore remains unclear. Few groups investigated Rapid Thermal Oxidation (RTO) (4) while most of them looked at furnace oxidation. Moreover, most studies only considered the initial Ge content to compare oxidation kinetics. Indeed, the Ge concentration below the SiGe-oxide interface is strongly varying with time because of two mechanisms: firstly, the Si-selective oxidation of SiGe tends to pile-up Ge below the oxidizing interface; and secondly, interdiffusion of SiGe favors homogenization of the layer (6). This paper focuses on the oxidation rate of SiGe in regards to the varying Ge concentration in the SiGe layer for various oxidation conditions. Thick (> 20 nm) SiGe layers with either 10% or 30% Ge concentrations were epitaxially grown on bulk Si wafers. Oxidation was performed by RTO in 1 atmosphere of pure O2, with different oxidation temperatures and durations. Oxide thickness and SiGe composition versus depth were measured by Spectroscopic Ellipsometry and X-Ray Reflectivity, and by Secondary Ion Mass Spectroscopy respectively. Figure 2 shows the Ge concentration profile below the oxide. A rapid creation of a pile-up layer is observed at all temperatures. Then, three regimes of evolution of the pile-up layer are distinguished: the Ge concentration at the oxidizing interface (a) increases, (b) is constant, and (c) decreases. The regime of evolution of the pile-up layer is determined by a competition between the oxidation speed and the interdiffusion speed. As schematically illustrated Figure 3, the interdiffusion speed overcomes the oxidation one at higher temperatures because the activation energy of interdiffusion in SiGe ([4,5] eV (7)) is well above the one of SiGe oxidation ([2,2.6] eV (4)). Phrased in a different way, the temperature dependence of interdiffusion is higher than the oxidation one. Figure 4 shows the oxide thickness versus the oxidation duration for dry RTO at 900°C, 1000°C and 1100°C. A higher oxidation rate is observed for SiGe compared to Si for all temperatures. Then, to highlight the effect of the Ge concentration at the oxidizing interface, we fitted the curves to extract oxidation rates for each oxidation conditions. We define the Growth Rate Enhancement (GRE) as the ratio of the oxidation rate of SiGe to the one of Si at a given oxide thickness and for identical oxidation conditions. It is indeed important to highlight that comparing oxidation rates at the same oxide thickness is mandatory: if we want to examine the effect of Ge on the oxidation rate, we have to take into consideration the fact that the oxidation rate also decreases with the oxide thickness. Such an approach allows us to freeze the system and to find more easily correlations. We report on Figure 5 four GRE values extracted from our data versus the Ge concentration at the oxidizing interface. We thus observe that the higher the Ge concentration at the oxidizing interface is, the higher the GRE tends to be. We thus showed that Ge redistribution by interdiffusion during SiGe oxidation can follow different regimes. We also evidenced that for dry RTO conditions, the higher the Ge concentration at the oxidizing interface is, the higher the GRE is. Understanding the interdependence of these two mechanisms is essential to get an accurate picture of the condensation process. Therefore, data for dry RTO will be completed and an in-depth discussion will be led. A similar study will also be conducted for a wet oxidation process called In-Situ Steam Generation (ISSG). (1) Pillarisetty, R., Nature 479.7373 (2011): 324-328. (2) Weber, O., et al., VLSIT IEEE, 2014. (3) Tezuka, T., et al., JJAP 40.4S (2001): 2866. (4) Spadafora, M., et al. MSSP 8.1 (2005): 219-224. (5) LeGoues, et al., APL 54.7 (1989): 644-646. (6) Long, E., et al., PSS (a) 209.10 (2012): 1934-1939. (7) Kube, R., et al., JAP 107.7 (2010): 073520. Figure 1

The isolation of a single layer of graphite, known today as graphene, not only demonstrated amazing new properties but also paved the way for a new class of materials often referred to as two-dimensional (2D) materials. Beyond graphene, other 2D materials include h-BN, transition metal dichalcogenides (TMDs), silicene, and germanene, to name a few. All tend to have exciting physical and chemical properties which appear due to dimensionality effects and modulation of their band structure. A more recent member of the 2D family is graphene-like zinc oxide (g-ZnO) which also holds great promise as a future functional material. This review examines current progress in the synthesis and characterization of g-ZnO. In addition, an overview of works dealing with the properties of g-ZnO both in its pristine form and modified forms (e.g., nano-ribbon, doped material, etc.) is presented. Finally, discussions/studies on the potential applications of g-ZnO are reviewed and discussed.

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.

PTEN (phosphatase and tensin homologue deleted on chromosome ten) proteins are dual phosphatases with both protein and phosphoinositide phosphatase activity. They modulate signalling pathways controlling growth, metabolism and apoptosis in animals and are implied in several human diseases. In the present paper we describe a novel class of PTEN pro-teins in plants, termed PTEN2, which comprises the AtPTEN (Arabidopsis PTEN) 2a and AtPTEN2b proteins in Arabidopsis. Both display low in vitro tyrosine phosphatase activity. In addition, AtPTEN2a actively dephosphorylates in vitro the 3′ phosphate group of PI3P (phosphatidylinositol 3-phosphate), PI(3,4)P2 (phosphatidylinositol 3,4-bisphosphate) and PI(3,5)P2 (phosphatidylinositol 3,5-bisphosphate). In contrast with animal PTENs, PI(3,4,5)P3 (phosphatidylinositol 3,4,5-trisphosphate) is a poor substrate. Site-directed mutagenesis of AtPTEN2a and molecular modelling of protein–phosphoinositide interactions indicated that substitutions at the PTEN2 core catalytic site of the Lys267 and Gly268 residues found in animals, which are critical for animal PTEN activity, by Met267 and Ala268 found in the eudicot PTEN2 are responsible for changes in substrate specificity. Remarkably, the AtPTEN2a protein also displays strong binding activity for PA (phosphatidic acid), a major lipid second messenger in plants. Promoter::GUS (β-glucuronidase) fusion, transcript and protein analyses further showed the transcriptional regulation of the ubiquitously expressed AtPTEN2a and AtPTEN2b by salt and osmotic stress. The results of the present study suggest a function for this novel class of plant PTEN proteins as an effector of lipid signalling in plants.

Carbon nanotubes are actively studied for thin-film transistor and electronics applications. Although these nanomaterials were first considered as potential candidates for the replacement of Si MOS type transistors in VLSI circuits, their main field of application is shifting towards large area electronics on flexible, plastic-type substrates, a domain which is at present, less demanding in terms of device dimensions and integration density. In particular, random networks of carbon nanotubes, which can be obtained by solution-processing or grown at low temperature, represent an attractive and viable option for the fabrication of electronic circuitry on non-refractory substrates. This paper briefly reviews some recent advances in the field, highlighting realisations beyond the fabrication of simple transistors.

Silicon exhibits the largest known capacity for Li insertion in anodes of Li-ion batteries. However, because of large volume expansion/phase changes upon alloying, Si becomes powder-like after a few charge-discharge cycles. Various approaches have been explored in the past to circumvent this problem, including the use of nanomaterials, particularly Si nanowires. However, even though nanowires resist cracking very well, anodes based on Si nanowires still see their original capacity fade away upon cycling, because of wire detachment from the substrate, due to the stress generated at their roots upon alloying with Li. Here, we present a silicon nanowire growth strategy yielding highly interconnected specimens, which prevents them from being individually detached from the substrate. We report a ∼ 100% charge retention after 40 cycles at C/2 rate, without charging voltage limitation. We also show that our anodes can be cycled at 8C rates without damage and we grow nanowires with a density of 1.2 mg/cm 2, yielding anodes delivering a 4.2 mAh/cm 2 charge density. Finally, we point out that a better understanding of the interactions of silicon with electrolytes is needed if the field is to progress in the future. © 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.

Tetrahydropterin-dependent aromatic amino acid hydroxylases (AAHs) are known from animals and microbes but not plants. A survey of genomes and ESTs revealed AAH-like sequences in gymnosperms, mosses, and algae. Analysis of full-length AAH cDNAs from Pinus taeda, Physcomitrella patens, and Chlamydomonas reinhardtii indicated that the encoded proteins form a distinct clade within the AAH family. These proteins were shown to have Phe hydroxylase activity by functional complementation of an Escherichia coli Tyr auxotroph and by enzyme assays. The P. taeda and P. patens AAHs were specific for Phe, required iron, showed Michaelian kinetics, and were active as monomers. Uniquely, they preferred 10-formyltetrahydrofolate to any physiological tetrahydropterin as cofactor and, consistent with preferring a folate cofactor, retained activity in complementation tests with tetrahydropterin-depleted E. coli host strains. Targeting assays in Arabidopsis thaliana mesophyll protoplasts using green fluorescent protein fusions, and import assays with purified Pisum sativum chloroplasts, indicated chloroplastic localization. Targeting assays further indicated that pterin-4a-carbinolamine dehydratase, which regenerates the AAH cofactor, is also chloroplastic. Ablating the single AAH gene in P. patens caused accumulation of Phe and caffeic acid esters. These data show that nonflowering plants have functional plastidial AAHs, establish an unprecedented electron donor role for a folate, and uncover a novel link between folate and aromatic metabolism.

We propose a novel growth technique, in which graphene is synthesized on capped Cu thin films deposited on c-plane sapphire. The cap is another sapphire plate which is just laid upon the Cu thin film, in direct contact with it. Thanks to this 'contact cap', Cu evaporation can be suppressed at high temperature and the 400 nm-thick Cu films can be annealed above 1000 °C, resulting in (1 1 1)-oriented grains of millimeter size. Following this high temperature annealing, graphene is grown by chemical vapor deposition during the same pump-down operation, without removing the contact cap. The orientation and doping type of the as-grown graphene were first studied, using low energy electron diffraction, as well as high resolution angle-resolved photoemission spectroscopy. In particular, the orientation relationships between the graphene and copper thin film with respect to the sapphire substrate were precisely determined. We find that the graphene sheets exhibit a minimal rotational disorder, with ~90% of the grains aligned along the copper high symmetry direction. Detailed transport measurements were also performed using field-effect transistor structures. Carrier mobility values as high as 8460 cm2 V−1 s−1 have been measured on top gate transistors fabricated directly on the sapphire substrate, by etching the Cu film from underneath the graphene sheets. This is by far the best carrier mobility value obtained to date for graphene sheets synthesized on a thin film-type metal substrate.

Tetrahydromonapterin is a major pterin in Escherichia coli and is hypothesized to be the cofactor for phenylalanine hydroxylase (PhhA) in Pseudomonas aeruginosa , but neither its biosynthetic origin nor its cofactor role has been clearly demonstrated. A comparative genomics analysis implicated the enigmatic folX and folM genes in tetrahydromonapterin synthesis via their phyletic distribution and chromosomal clustering patterns. folX encodes dihydroneopterin triphosphate epimerase, which interconverts dihydroneopterin triphosphate and dihydromonapterin triphosphate. folM encodes an unusual short-chain dehydrogenase/reductase known to have dihydrofolate and dihydrobiopterin reductase activity. The roles of FolX and FolM were tested experimentally first in E. coli , which lacks PhhA and in which the expression of P. aeruginosa PhhA plus the recycling enzyme pterin 4a-carbinolamine dehydratase, PhhB, rescues tyrosine auxotrophy. This rescue was abrogated by deleting folX or folM and restored by expressing the deleted gene from a plasmid. The folX deletion selectively eliminated tetrahydromonapterin production, which far exceeded folate production. Purified FolM showed high, NADPH-dependent dihydromonapterin reductase activity. These results were substantiated in P. aeruginosa by deleting tyrA (making PhhA the sole source of tyrosine) and folX . The Δ tyrA strain was, as expected, prototrophic for tyrosine, whereas the Δ tyrA Δ folX strain was auxotrophic. As in E. coli , the folX deletant lacked tetrahydromonapterin. Collectively, these data establish that tetrahydromonapterin formation requires both FolX and FolM, that tetrahydromonapterin is the physiological cofactor for PhhA, and that tetrahydromonapterin can outrank folate as an end product of pterin biosynthesis.

Like other forms of engineering, metabolic engineering requires knowledge of the components (the ‘parts list’) of the target system. Lack of such knowledge impairs both rational engineering design and diagnosis of the reasons for failures; it also poses problems for the related field of metabolic reconstruction, which uses a cell's parts list to recreate its metabolic activities in silico. Despite spectacular progress in genome sequencing, the parts lists for most organisms that we seek to manipulate remain highly incomplete, due to the dual problem of ‘unknown’ proteins and ‘orphan’ enzymes. The former are all the proteins deduced from genome sequence that have no known function, and the latter are all the enzymes described in the literature (and often catalogued in the EC database) for which no corresponding gene has been reported. Unknown proteins constitute up to about half of the proteins in prokaryotic genomes, and much more than this in higher plants and animals. Orphan enzymes make up more than a third of the EC database. Attacking the ‘missing parts list’ problem is accordingly one of the great challenges for post-genomic biology, and a tremendous opportunity to discover new facets of life's machinery. Success will require a co-ordinated community-wide attack, sustained over years. In this attack, comparative genomics is probably the single most effective strategy, for it can reliably predict functions for unknown proteins and genes for orphan enzymes. Furthermore, it is cost-efficient and increasingly straightforward to deploy owing to a proliferation of databases and associated tools.

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.

[*] Dr. J.-Y. Choi, H.-J. Shin, S.-M. Yoon Display Device and Processing Laboratory Samsung Advanced Institute of Technology PO Box 111, Suwon 440-600 (Republic of Korea) E-mail: jaeyoung88.choi@samsung.com Prof. Y. H. Lee, S. J. Chae, F. Gunes, Dr. K. K. Kim, E. S. Kim, G. H. Han, S. M. Kim, H.-J. Shin BK21 Physics Division Sungkyunkwan Advanced Institute of Nanotechnology Center for Nanotubes and Nanostructured Composites Sungkyunkwan University Suwon 440-746 (Republic of Korea) E-mail: leeyoung@skku.edu M. H. Park, Prof. C. W. Yang Department of Advanced Materials Engineering Sungkyunkwan University Suwon 440-746 (Republic of Korea)

This paper deals with the fabrication of carbon nanotube field effect transistors (CNTFETs) for gas sensing applications. Such devices exploit the extremely sensitive change of the Schottky barrier heights between carbon nanotubes (CNTs) and drain/source metal electrodes: the gas adsorption creates an interfacial dipole that modifies the metal work function and so the band bending and the height of the Schottky barrier at the contacts. Our aim is to achieve the fingerprinting of a specific gas using a CNTFET based sensor array. This fingerprinting concept is based on the fact that the change of the metal electrode work function strictly depends on the metal/gas interaction. Consequently the CNTFET transfer characteristics will change specifically as a function of this interaction. To demonstrate this new concept, we have fabricated arrays of CNTFETs with different metal contacts: Au, Pd, Ti and Pt. Using these transistors, we have shown that a particular gas, in our case DiMethyl-Methyl-Phosphonate (DMMP,...

The effects of an atomic hydrogen ( H at ) pretreatment of the catalyst layer on the low temperature growth of single-walled carbon nanotubes (SWCNTs) have been investigated using a modified catalytic chemical vapor deposition system. Well-defined and isolated individual Fe nanoparticles as a catalyst are successfully formed on the defects with high trapping energy which are created on the Al 2 O 3 surface by H at pretreatment, yielding highly dense SWCNTs. The pretreatment mechanism of H at , compared to H 2 , is also discussed. It was also found that the quality of SWCNTs can be enhanced when H at is flowed with CH 4 during nanotubes growth at low temperature. In this case, the undesired carbon products and defects on catalyst seeds and nanotube walls can be selectively removed by H at . Therefore it is essential to use H at in the pretreatment stage for increasing catalytic activity and to keep the size of nanoparticles in the nm range. H at can also be employed in growth stage for enhancing SWCNTs quality and density at low temperature.

International audience; Ce guide (et sa synthèse) s'inscrit dans la phase 3 de l'Initiative Française pour les Récifs Coralliens (IFRECOR), Les échanges d'informations de plus en plus important entre les différents acteurs rendent nécessaire l'harmonisation et la standardisation des cartes réalisées et utilisées par les gestionnaires. Ainsi, ce guide fournit à ces derniers :− les notions clefs pour mieux appréhender une carte d'habitats des récifs coralliens ;− la démarche pour réaliser une carte d'habitats et rédiger un cahier des charges ;− les critères de normalisation.Afin de disposer d'une carte répondant aux objectifs variés des gestionnaires, le guide aborde plus particulièrement les différentes actions à mettre en œuvre tels que : le choix de l'échelle de restitution, de l'image et du niveau de détail des habitats, les méthodes de « vérité terrain », les méthodes de traitement d'image, la construction de la typologie finale, les moyens nécessaires (humains, techniques et financiers) et les délais pour la réalisation d'une carte.Enfin, différents critères de normalisation des cartes sont définis dans le guide et concernent :− la construction hiérarchique de la typologie en fonction de l'échelle de restitution ;− la « vérité terrain » ;− la construction de la typologie finale et la justesse de la carte ;− les formats de rendu des différents documents.