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Various SF6/Ar plasma-textured periodic glass surface morphologies for high transmittance, haze ratio and low sheet resistance of ITO:Zr films are reported. The SF6/Ar plasma-textured glass surface morphologies were changed from low aspect ratio to high aspect ratio with the increase in RF power from 500 to 600 W. The micro- and nano-size features of textured glass surface morphologies enhanced the haze ratio in visible as well as NIR wavelength region. Micro-size textured features also influenced the sheet resistance and electrical characteristics of ITO:Zr films due to step coverage. The ITO:Zr/AZO bilayer was used as front TCO electrode for p-i-n amorphous silicon thin film solar cells with current density–voltage characteristics as: V oc = 875 mV, FF = 70.90 %, J sc = 11.31 mA/cm2, η = 7.02 %.

A paralog (here termed COG0212) of the ATP-dependent folate salvage enzyme 5-formyltetrahydrofolate cycloligase (5-FCL) occurs in all domains of life and, although typically annotated as 5-FCL in pro- and eukaryotic genomes, is of unknown function. COG0212 is similar in overall structure to 5-FCL, particularly in the substrate binding region, and has distant similarity to other kinases. The Arabidopsis thaliana COG0212 protein was shown to be targeted to chloroplasts and to be required for embryo viability. Comparative genomic analysis revealed that a high proportion (19%) of archaeal and bacterial COG0212 genes are clustered on the chromosome with various genes implicated in thiamin metabolism or transport but showed no such association between COG0212 and folate metabolism. Consistent with the bioinformatic evidence for a role in thiamin metabolism, ablating COG0212 in the archaeon Haloferax volcanii caused accumulation of thiamin monophosphate. Biochemical and functional complementation tests of several known and hypothetical thiamin-related activities (involving thiamin, its breakdown products, and their phosphates) were, however, negative. Also consistent with the bioinformatic evidence, the COG0212 proteins from A. thaliana and prokaryote sources lacked 5-FCL activity in vitro and did not complement the growth defect or the characteristic 5-formyltetrahydrofolate accumulation of a 5-FCL-deficient (ΔygfA) Escherichia coli strain. We therefore propose (a) that COG0212 has an unrecognized yet sometimes crucial role in thiamin metabolism, most probably in salvage or detoxification, and (b) that is not a 5-FCL and should no longer be so annotated.

International audience; The electrochemical and structural responses of silicon nanowires deposited by chemical vapor deposition are investigated. Transmission electron microscopy and X-ray diffraction experiments show the electrochemical lithiation of SiNWs is not a quantitative process in good agreement with cycling experiments performed as a function of cycling limits. The SiNWs are not deeply lithiated as revealed by TEM micrographs. Our results suggest the existence of two well-defined lithiation steps, first at ∼0.2 V into amorphous silicon and then into crystalline silicon at ∼0.1 V. Cycling SiNWs above 100 mV avoid the lithiation of c-Si which preserves the silicon 3-D architecture and results in good cycling performances. A stable capacity value of ∼500 mAh g−1 is achieved over at least 50 cycles.

In this work, the excimer-laser-induced crystallization of a-Si films on SiO2 was investigated using a long-pulse-duration (200 ns) XeCl source. The microstructural analysis of the laser-irradiated area, for incident energy densities comprised between the thresholds corresponding to the surface and full melting, respectively, of the Si layer, was performed by scanning electron microscopy and Raman spectroscopy. A super-lateral-growth regime was evidenced quite comparable to that which occurs when classical excimer laser pulses of short duration (≈20 ns) are used. A numerical simulation of the surface melt dynamics was also performed and compared to the experimental observations.

This paper deals with preliminary measurements for prove-of-concept of a Carbon Nanotubes Field Effect Transistors (CNTFETs) based sensor array which could improve dramatically gas selectivity. CNTFET based sensors exploit the extremely sensitive change of the Schottky barrier heights between Single Wall Carbon NanoTubes (SWCNTs) and drain/source metal electrodes: the gas adsorption creates an interfacial dipole that modifies the metal work function and so the bending and the height of the Schottky barrier at the contacts [1,2]. Using CNTFET array fabricated using SWCNT mat as channel, we have achieved a sort of electronic fingerprinting of different gases. Actually, we want to demonstrate that the change of the metal electrode work function strictly depends on the metal/gas interaction : CNTFET transfer characteristics will change specifically as a function of this interaction. In this study we have fabricated different CNTFETs using three metal contacts (Au, Pd, Mo) and exposed them to two gases, DMMP and NH3, which have the same “electron-withdrawing” behavior. The CNTFETs array has been exposed to 1ppm of DMMP and 10ppm NH3 and we have identified two electronic fingerprinting. The totality of our measures have been performed at ambient conditions.

In order to utilise the full potential of carbon nanotubes/nanofibers, it is necessary to be able to synthesize well aligned nanotubes/nanofibres at desired locations on a substrate. This paper examines the preferential growth of aligned carbon nanofibres by PECVD using lithographically patterned catalysts. In the PECVD deposition process, amorphous carbon is deposited together with the nanotubes due to the plasma decomposition of the carbon feed gas, in this case, acetylene. The challenge is to uniformly nucleate nanotubes and reduce the unwanted amorphous carbon on both the patterned and unpatterned areas. An etching gas (ammonia) is thus also incorporated into the PECVD process and by appropriately balancing the acetylene to ammonia ratio, conditions are obtained where no unwanted amorphous carbon is deposited. In this paper, we demonstrate high yield, uniform, ‘clean’ and preferential growth of vertically aligned nanotubes using PECVD.

Plasma Enhanced Chemical Vapour Deposition is an extremely versatile technique for directly growing multiwalled carbon nanotubes onto various substrates. We will demonstrate the deposition of vertically aligned nanotube arrays, sparsely or densely populated nanotube forests, and precisely patterned arrays of nanotubes. The high-aspect ratio nanotubes (~50 nm in diameter and 5 microns long) produced are metallic in nature and direct contact electrical measurements reveal that each nanotube has a current carrying capacity of 107-108 A/cm2, making them excellent candidates as field emission sources. We examined the field emission characteristics of dense nanotube forests as well as sparse nanotube forests and found that the sparse forests had significantly lower turn-on fields and higher emission currents. This is due to a reduction in the field enhancement of the nanotubes due to electric field shielding from adjacent nanotubes in the dense nanotube arrays. We thus fabricated a uniform array of single nanotubes to attempt to overcome these issues and will present the field emission characteristics of this.

Conformal epitaxy is an epitaxial growth technique capable of yielding low dislocation density III-V films on Silicon. In this technique, the growth of the III-V material occurs parallel to the silicon substrate, from the edge of a previously deposited III-V seed, the vertical growth being stopped by an overhanging capping layer. As an example, conformal GaAs layers on Silicon, presenting dislocation densities below 105cm−2, have been obtained using selective vapor phase epitaxy. These layers have then been used as high quality GaAs on Si substrates for subsequent vertical MBE regrowth of active structures. In this paper, we report on the integration of surface-emitting microcavity LEDs with their silicon drivers using this conformal growth technique. The global technology concept and the design of the active structures are first presented. The compatibility of the conformal growth technique with CMOS technology is then checked: the impact of the integration process on the performances of the drivers is for example quantified. Characterisations of the high crystalline quality of the conformal layers and of the LEDs structures grown on it are then shown. The electro-optical characteristics of the LEDs on Si are finally compared to those of reference LEDs on GaAs substrates in order to prove the efficiency of the integration procedure.

In this paper, we essentially discuss the material aspects of low temperature (≤ 600 °C) polysilicon technologies. Emphasis is put on the properties of polysilicon films, depending on the way they are obtained. Solid phase crystallisation as well as pulsed laser crystallisation processes are presented in some detail, together with thin film transistor characteristics. Although not yet stabilised and despite uniformity and reproducibility problems, laser crystallisation will probably end up being the technology of choice for the manufacture of large area electronics products, because it allows the fabrication of devices exhibiting superior properties, with a reduced thermal budget.

Low temperature deposition of dielectric thin films is more and more used in very largescale integrated (VLSI) circuits. For this purpose, distributed electron cyclotron resonance (DECR) plasma appears to be a promising tool. The most interesting feature of this recent plasma is the high ion density (≈1011 cm−3) associated with low electronic temperature (2–3eV) and low energy species (20–30 eV). The purpose of this study is to discuss the effects of the reactant gas mixture composition (O2sol;SiH4) and the rf substrate bias power on the physical, chemical and electrical properties of DECR SiO2 films deposited at floating temperature (

Conformal growth is a confined epitaxial lateral overgrowth technique capable of yielding low dislocation density GaAs films on Si. This technique makes extensive use of selective epitaxy and crystal growth is confined by a dielectric cap as well as by the self-passivated Si surface itself.In this paper, we have performed a detailed characterisation of the state of stress of the GaAs films in various configurations (after conformal growth and removal of the seed regions, and after the regrowth of an MBE layer) by photoluminescence measurements at 5K and X-ray diffraction experiments. Although the as-grown conformal films are found in the same state of stress than reference MOCVD GaAs epilayers on Si, we report a significant decrease of this stress after MBE regrowth on conformal films.

Current-voltage, capacitance-voltage and defect spectroscopy techniques are used to characterize the electrical properties of GaAs crystals after pulsed laser irradiation with either a Nd-YAG or a Ruby laser. I(V) and C(V) measurements performed in conjunction on Au/GaAs Schottky structures after laser irradiation at low energy density show an important barrier lowering, of the order of 300mV. Carrier compensation up to 6×lO16/cm3 is observed in a subsurface layer whose thickness increases with deposited laser energy density. D.L.T.S. is used to study the tail of laser induced defects behind the heavily compensated layer. Finally the results are compared to those obtained following conventional thermal treatment.

We have studied silicon incorporation in GaAs subsequent to Nd-YAG laser irradiation through high pressure silane atmospheres. The process involves SiH4 pyrolysis at contact with a laser-melted GaAs surface, and incorporation of the released Si atoms in the melt. SIMS analyses have allowed us to study silicon incorporation as a function of SiH4 pressure, laser energy density and number of laser shots. The high sheet resistance of the doped layers indicates that the silicon atoms are poorly electrically activated. A compensation mechanism is discussed based on oxygen penetration from native GaAs oxide layers.

Astract(100) single crystal silicon films have been deposited onto (100) oriented Yttria-Stabilized Zirconia (YSZ) substrates by pyrolysis of SiH4 at ∼ 980°C.The as deposited epitaxial silicon films have been characterized by Reflexion High Energy Electron Diffraction and Transmission Electron Microscopy techniques.The as deposited silicon films have also been oxidized by oxygen transport through the substrate, resulting in a Si(100)/ amorphous SiO2/YSZ(100) structure in which the most defective part of the epitaxial silicon deposit has been eliminated. The oxidized interfaces (with SiO2 thicknesses in the 2000 Å range) have then been characterized by Transmission Electron Microscopy in order to assess the improvement in crystalline quality. Electrical measurements have also been performed on MOS-Hall bar structures.

We have studied the effects of pulsed laser irradiation on silicon implanted, thermally activated , Calcia Stabilized Zirconia (CSZ) capped GaAs substrates. Reference substrates have also been irradiated in air for comparison. CSZ as a solid electrolyte has been used to chemically reduce the GaAs surface native oxides prior to irradiation while maintaining the surface stoechiometry. Our results indicate a spectacular decrease in defect density after laser irradiation of the CSZ capped-native oxide free samples, as compared to the samples irradiated in air.