First-principles study of n-type dopants and their clustering in SiC

We report the results of an ab initio study of N and P dopants in SiC. We find that while N substitutes most favorably at a C lattice site, P does so preferably at a Si site, except in n-doping and Si-rich 3C-SiC. Furthermore, we consider a series of dopant complexes that could form in high-dose implantation, in order to investigate the dopant activation behavior in this limit. We find that all N complexes considered lead to passivation through the formation of a deep level. For P, the most stable aggregate is still an active dopant, while passivation is only observed for complexes with a higher formation energy. We discuss how these results could help in the understanding of the observed experimental high-dose doping and codoping behavior of these species

Theoretical evidence for the kick-out mechanism for B diffusion in SiC

In this letter, we analyze by means of first-principles electronic structure calculations the diffusion of B impurities in 3C-SiC. We find, through molecular dynamics, that substitutional B at a Si lattice site is readily displaced by a nearby Si interstitial by the process known as a kick-out mechanism, in agreement with recent experimental results. This is in contrast to the situation in Si, where B has recently been shown to diffuse via an interstitialcy mechanism

Viévy-le-Rayé – Le Parlement

À la demande de la Communauté de communes Beauce Val de Loire, l’Inrap a été sollicité pour une expertise historique sur les ruines du site du Parlement à Viévy-le-Rayé (Loir-et-Cher), associant un relevé photogrammétrique du site, une prospection géophysique et une enquête documentaire. L’intervention s’est fixée pour objectif d’établir un plan précis des vestiges visibles et des anomalies géophysiques. En raison de son toponyme évocateur, la tradition locale associe le site du Parlement à u..

Performance of neutron-irradiated 4H-Silicon Carbide diodes subjected to Alpha radiation

The unique electrical and material properties of 4H-silicon-carbide (4H-SiC) make it a promising candidate material for high rate particle detectors. In contrast to the ubiquitously used silicon (Si), 4H-SiC offers a higher carrier saturation velocity and larger breakdown voltage, enabling a high intrinsic time resolution and mitigating pile-up effects. Additionally, as radiation hardness requirements grow more demanding, wide-bandgap materials such as 4H-SiC could offer better performance. In this work, the detector performance of 50 micron thick 4H-SiC p-in-n planar pad sensors was investigated at room temperature, using an 241Am alpha source at reverse biases of up to 1100 V. Samples subjected to neutron irradiation with fluences of up to 1e16/cm^2 were included in the study in order to quantify the radiation hardness properties of 4H-SiC. The obtained results are compared to previously performed UV-TCT studies. Samples exhibit a drop in charge collection efficiency (CCE) with increasing irradiation fluence, partially compensated at high reverse bias voltages far above full depletion voltage. A plateau of the collected charges is observed in accordance with the depletion of the volume the alpha particles penetrate for an unirradiated reference detector. For the neutron-irradiated samples, such a plateau only becomes apparent at higher reverse bias. For the highest investigated fluence, CCE behaves almost linearly with increasing reverse bias. Compared to UV-TCT measurements, the reverse bias required to deplete a sensitive volume covering full energy deposition is lower, due to the small penetration depth of the alpha particles. At the highest reverse bias, the measured CCE values agree well with earlier UV-TCT studies, with discrepancies between 1% and 5%.Comment: 10 pages (8 without references), 6 figures, 1 table, to be published in the Proceedings Section of Journal of Instrumentation (JINST) as a proceeding of iWoRiD202

Silicon Carbide Controlled Current Limiter, Current Limitation Strategies, Foreseen Applications and Benefits

International audienceThe expansion of electricity networks (distribution of energy, telecommunication), strongly contributed to increase the risks of appearance of defects, such as surge or overload. This multiplicity and complexity of electric networks, the need to have reliable systems favoured the development of serial protection devices. Fuse solution allows an efficient and total protection but requires to replace an element in case of failure. Therefore, other solutions have been investigated. Complex systems have been developed, all based on serial compensation, such as supra-conductor material, GTO MOV combination ... Indeed, because of the strong energy appearance during a short circuit, it is necessary to limit and to dissipate the energy of the short circuit, under high bias. This constraint leads to a feasibility study of a current limiter in 4H silicon carbide (4H-SiC). A VJFET structure was retained focusing on a nominal current of IN = 1 A and a nominal voltage of VN = 690 V. The device was optimised, taking into account SiC excellent physical properties. The VJFET was designed checking the trade-off between a low on-resistance value, high voltage capability and the highest gate transconductance value. A first batch of component was made, validating the bi-directional limitation function in both current and voltage mode, (VMAX = 970 V). The efficiency of the protection was validated, demonstrating the capacity of a component to react very quickly (t < 1 µs). Using such a device is very suitable in several applications (protection against short circuit, transient over current…) as it will allow to reduce transient phenomena and thus increase the efficiency and lifetime of the whole system

Optical nano-imaging of gate-tunable graphene plasmons

arXiv:1202.4996.-- et al.The ability to manipulate optical fields and the energy flow of light is central to modern information and communication technologies, as well as quantum information processing schemes. However, because photons do not possess charge, a way of controlling them efficiently by electrical means has so far proved elusive. A promising way to achieve electric control of light could be through plasmon polaritons-coupled excitations of photons and charge carriers-in graphene. In this two-dimensional sheet of carbon atoms, it is expected that plasmon polaritons and their associated optical fields can readily be tuned electrically by varying the graphene carrier density. Although evidence of optical graphene plasmon resonances has recently been obtained spectroscopically, no experiments so far have directly resolved propagating plasmons in real space. Here we launch and detect propagating optical plasmons in tapered graphene nanostructures using near-field scattering microscopy with infrared excitation light. We provide real-space images of plasmon fields, and find that the extracted plasmon wavelength is very short-more than 40 times smaller than the wavelength of illumination. We exploit this strong optical field confinement to turn a graphene nanostructure into a tunable resonant plasmonic cavity with extremely small mode volume. The cavity resonance is controlled in situ by gating the graphene, and in particular, complete switching on and off of the plasmon modes is demonstrated, thus paving the way towards graphene-based optical transistors. This successful alliance between nanoelectronics and nano-optics enables the development of active subwavelength-scale optics and a plethora of nano-optoelectronic devices and functionalities, such as tunable metamaterials, nanoscale optical processing, and strongly enhanced light-matter interactions for quantum devices and biosensing applications. © 2012 Macmillan Publishers Limited. All rights reserved.This work was supported in part by the Fundacicio Cellex Barcelona, the Spanish MICINN (MAT2010-14885 and Consolider NanoLight.es), the European FP7 projects FP7-HEALTH-F5-2009-241818-NANOANTENNA, FP7-ICT- 2009-4-248909-LIMA and FP7-ICT-2009-4-248855-N4E, the ERC Starting grant no. 258461 (TERATOMO), and the ERC Career integration grant GRANOP.Peer Reviewe

Bidirectional Modulation of Neuronal Cells Electrical and Mechanical Properties Through Pristine and Functionalized Graphene Substrates

[Abstract] In recent years, the quest for surface modifications to promote neuronal cell interfacing and modulation has risen. This course is justified by the requirements of emerging technological and medical approaches attempting to effectively interact with central nervous system cells, as in the case of brain-machine interfaces or neuroprosthetic. In that regard, the remarkable cytocompatibility and ease of chemical functionalization characterizing surface-immobilized graphene-based nanomaterials (GBNs) make them increasingly appealing for these purposes. Here, we compared the (morpho)mechanical and functional adaptation of rat primary hippocampal neurons when interfaced with surfaces covered with pristine single-layer graphene (pSLG) and phenylacetic acid-functionalized single-layer graphene (fSLG). Our results confirmed the intrinsic ability of glass-supported single-layer graphene to boost neuronal activity highlighting, conversely, the downturn inducible by the surface insertion of phenylacetic acid moieties. fSLG-interfaced neurons showed a significant reduction in spontaneous postsynaptic currents (PSCs), coupled to reduced cell stiffness and altered focal adhesion organization compared to control samples. Overall, we have here demonstrated that graphene substrates, both pristine and functionalized, could be alternatively used to intrinsically promote or depress neuronal activity in primary hippocampal cultures.This work was funded by the European Union’s Horizon 2020 Research and Innovation Program under the Grant Agreements 785219 and 881603 of the Graphene Flagship. DS acknowledges the support of the European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie grant agreement no. 838902. MP as the recipient of the AXA Bionanotechnology Chair, is grateful to the AXA Research Fund for financial support. This work was performed under the Maria de Maeztu Units of Excellence Program from the Spanish State Research Agency-grant no. MDM-2017- 0720. AC thanks Xunta de Galicia for his research grant Atracción de Talento (no. ED431H 2020/17). GR acknowledges funding from RYC-2016-21412. HH acknowledges funding from Juan de la Cierva – Incorporación no. IJC-2018-037396-IXunta de Galicia; ED431H 2020/1

Carbon Nanotubes as Suitable Interface for Improving Neural Recordings

In the last decades, system neuroscientists around the world have dedicated their research to understand how neuronal networks work and how they malfunction in various diseases. Furthermore in the last years we have seen a progressively increased interaction of brain networks with external devices either for the use of brain computer interfaces or through the currently extended brain stimulation (e.g. transcranial magnetic stimulation) for therapy. Both techniques have evidenced even more the need for a better understanding of neuronal networks. These studies have resulted in the development of different strategies to understand the ongoing neuronal activity, such as fluorescence microscopy for genetic labelling and optogenetic techniques, imaging techniques, or the recording/stimulation with increasingly large numbers of electrodes in the whole brain or in both cell cultured neurons and slice preparations. It is in these last two areas where the technology developed on microelectrode arrays, commonly called multi-electrode arrays (MEAs), has become important over other technologie

Pushing the Limits of Space Technology

Coordinators: Philippe Godignon; Gustavo Liñán.Peer reviewe