Influence of P+ layer parameters on 4H-SiC UV PiN photodetector characteristics

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Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

Simulation, réalisation et caractérisation de jonction p+n en SiC-4H, pour la photodétection de rayonnement UV

Le SiC est un matériau semi-conducteur à large bande d'énergie interdite dont les très bonnes caractéristiques électriques et thermiques en font un candidat idéal pour la fabrication de composants dans le domaine de la puissance et des détecteurs de rayonnement. En particulier, la réalisation de détecteurs UV est très attendue dans les domaines suivants : détection d'incendies, imagerie de surface, astronomie, médecine, militaire… Les photodétecteurs à base de semiconducteurs à large bande interdite permettent d'obtenir une très bonne sélectivité dans l'UV, sans avoir à utiliser de filtres optiques. Le SiC semble être le matériau le plus prometteur, grâce à sa bonne stabilité chimique, mécanique et thermique, ce qui représente un avantage pour opérer en environnement extrême. Cependant le dopage du SiC nécessite un savoir-faire très particulier (implantation à chaud, recuit à haute température, forte dynamique de chauffe…). Nous nous sommes proposés dans un premier temps de réaliser par implantation (ionique et plasma) des composants tests, permettant d'accéder aux caractéristiques des jonctions. Le cas des jonctions implantées n+p et p+n a été étudié. Après l'optimisation des paramètres technologiques de l'implantation et du recuit associé, la fabrication de détecteurs de rayonnement basés sur la diode Schottky ou la diode p.n a été mise en œuvre. Une étape de simulation de ces composants a été effectuée sur le logiciel Sentaurus Device (Synopsys). Les caractérisations de ces détecteurs ont montré une meilleure sensibilité pour les diodes implantées Bore par plasma.Silicon carbide is a wide band-gap semiconductor with electrical and thermal characteristics particularly suitable for high power devices and radiation sensors. The realisation of UV detectors is mainly useful in the following sectors: fire detection, surface imagery, astronomy, medicine, military... The photodetectors based on wide band-gap semiconductors allow to get a very good selectivity, without using optical filters. Silicon carbide seems to be the most promising material, due to its chemical, mechanical and thermal stability, inducing a reliable behaviour in extreme environment. However SiC doping requires a distinct know-how (hot ion implantation, high temperature annealing, rapid heating-rate…). Test devices have been firstly processed by using ion implantation and plasma, allowing evaluating p+n or n+p junction characteristics. After the optimisation of the technological parameters of implantation and related annealing, the realisation of radiation detectors based on Schottky or p.n diodes has been carried out. The electrical simulations of such devices were performed with Sentaurus Devices program (Synopsys). The characteristics of the devices proved an improvement with the Boron-plasma implantation

Chemical contamination along the Mediterranean French coast using Posidonia oceanica (L.) Delile above-ground tissues: a multiple trace element study

Levels of Be, Al, V, Mn, Co, As, Se, Mo, Ag, Sn, Sb, Bi as well as of Cr, Fe, Ni, Cu, Zn, Cd and Pb in Posidonia oceanica (L.) Delile from the Mediterranean French coast were analysed using DRC ICP-MS. The first twelve elements have not been well studied and can be considered to be potential pollutants as a result of potentially increased levels resulting from anthropogenic activities. Spatial variation and/or compartmentalization were found for all trace elements. Except for Al, Cr, Fe, Cu and Ag, most trace elements were preferentially accumulated in photosynthetic tissues, suggesting uptake from the water column. Moreover, for Be, V, Mn, Co, Ni, As, Mo, Sb, Sn and Pb, adult leaves had higher levels than intermediate leaves, suggesting low kinetics of accumulation. Levels in the third intermediate leaf were representative of the average levels of the integral shoot, and thus can be used alone in chemical biomonitoring. For most of the twelve little-studied trace elements, the background levels of the northwestern Mediterranean Sea can be measured, and their spatial variation can be related to anthropogenic activities. Levels of the seven widely studied trace elements seem to decrease or stabilize over time, probably due to their reduced anthropogenic use. These observations show that P. oceanica is a sensitive bioindicator for the monitoring of chemical contamination of a large number of trace elements.PhD thesis. Coastal pollution of the Mediterranean and extension of its biomonitoring to trace elements of emerging concer

Influence on electrical characteristics of the design of 4H-SiC ultraviolet photodetectors: Theoretical analysis and simulations

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Optical and Electrical Simulation of 4H-SiC UV Photodetector by Finite Element Method

International audienceThis paper focuses on UV-photodetector simulation. The calculus method description and the physical equations which occur in this model are presented as well as the UV-photodetector structure (p+n--n+ diode). Based on the Finite Element Method the electrical part solves the continuity and Poisson equation, and the optical part solves by Maxwell’s equation, FDTD [1]. Simulation works point out the influence of the p+-type layer on the electrical characteristics such as the current densities versus reverse bias. Indeed, simulation results show the current density increase with the decrease doping concentration or the p+-type layer thickness

Influence of Heating and Cooling Rates of Post-Implantation Annealing Process on Al-Implanted 4H-SiC Epitaxial Samples

International audienceWe report on topographical, structural and electrical measurements of aluminum-implanted and annealed 4H-SiC epitaxial samples. The influence of heating-up and cooling-down temperature rates on the SiC surface roughness, the crystal volume reordering and the dopant electrical activation was particularly studied. A higher heating-rate was found to preserve the rms roughness for annealing temperatures lower than 1700°C, and to improve the sheet resistance whatever the annealing temperature due to a better dopant activation (except for 1600°C process, which induced a dark zone in the sample volume). A complete activation was calculated for an annealing at 1700°C during 30 minutes, with a ramp-up at 20°C/s. Rising the cooling-down rate appeared to increase the sheet resistance, probably due to a higher concentration of point defects in the implanted layer

Posidonia oceanica (L.) Delile, un outil adéquat pour l'étude de la contamination chimique du littoral méditérranéen: application aux éléments traces

peer reviewedThe concentrations of 19 trace elements (TE): Be, Al, V, Mn, Co, As, Se, Mo, Ag, Sn, Sb and Bi as well as Cr, Fe, Ni, Cu, Zn, Cd and Pb, were analyzed by DRC ICP-MS in Posidonia oceanica (L.) Delile leaves from the Mediterranean French coast. The first 12 TE have little been studied nowadays. Except for Al, Cr, Fe, Cu and Ag, TE were preferentially accumulated in photosynthetic part of leaves. Moreover, trace element concentrations of the third intermediate leaf are representative of the integral shoot, and could be used alone in biomonitoring. Environmental background concentrations of the 12 little studied TE were determined, and spatial variations were related to anthropic activities. Compared to previous publications, concentrations of the 7 other TE classically investigated present a diminution or a stabilization, reflecting the change of anthropogenic inflows. In conclusion, P. oceanica is a sensitive bioindicator for chemical contamination, even for the twelve little studied TE

Distribution of inorganic carbon and related parameters in surface waters of the English Channel during spring 1994

The complete CO2 system, dissolved oxygen, nutrients and chlorophyll concentrations, fluorescence, salinity and temperature of surface seawater have been determined in the English Channel and the Southern Bight of the North Sea during Spring 1994. As already mentioned in a previous study, this area is characterized by important spatial and temporal variations of the considered set of parameters. This paper focuses on the distribution of the homogeneous buffer factor [β = dln(pCO2)dln(TCO2)]. It is shown that this parameter is a useful tool for identifying processes that mainly affect the CO2 distribution, such as primary production or water mass mixing, even in such a complex area