52 research outputs found
Injecteur optimisé pour l'épitaxie par jet chimique
LâĂ©pitaxie par jet chimique (ĂJC) est une mĂ©thode de fabrication de semi-conducteur qui permet dâamener Ă un volume de production des matĂ©riaux de pointes qui sont normalement limitĂ©s aux rĂ©acteurs dâĂ©pitaxie par jet molĂ©culaire (ĂJM). Lâun des aspects Ă amĂ©liorer des rĂ©acteurs ĂJC est le faible pourcentage de gaz injectĂ©, autour de 5 %, qui atteint le substrat afin de participer Ă la croissance du semi-conducteur. Mais comment amĂ©liorer lâefficacitĂ© dâinjection des gaz de ces rĂ©acteurs? Tout dâabord, il a Ă©tĂ© possible dâadapter un outil de modĂ©lisation de performances dâinjecteur afin de dĂ©velopper un nouveau concept. Cet outil a Ă©tĂ© validĂ© par un prototype simplifiĂ© Ă lâintĂ©rieur dâune chambre dâessai Ă©quipĂ©e dâinstruments de caractĂ©risation. Par la suite, il y a eu la conception dâun injecteur optimisĂ©, la conception dâun systĂšme dâassemblage, la conception dâun systĂšme de gestion de tempĂ©rature et finalement, la validation expĂ©rimentale de tous les systĂšmes. Avec des efficacitĂ©s dâinjection dâenviron 29 % pour les rĂ©actifs du groupe III et de 37 % pour le groupe V, ce projet permet de rĂ©aliser un rĂ©acteur amĂ©liorant lâefficacitĂ© dâinjection, le taux de croissance, les coĂ»ts de production et diminuant les rejets chimiques. La non-uniformitĂ© dâinjection est pour sa part en dessous des objectifs fixĂ©s avec 13 % pour le groupe III et de 24 % pour le groupe V. LâefficacitĂ© dâinjection est dĂ©finie comme Ă©tant le pourcentage de molĂ©cule injectĂ©e atteignant directement le substrat. La non-uniformitĂ© est dĂ©finie comme Ă©tant le ratio entre lâĂ©cart-type du flux de gaz sur le substrat et lâintensitĂ© la plus faible atteignant celui-ci. Ce projet a permis de valider ou dâĂ©carter plusieurs hypothĂšses initiales permettant ainsi dâamĂ©liorer les outils de simulations et de conceptions dâinjection du laboratoire. La croissance sans rotation sâest avĂ©rĂ©e possible en atteignant des performances similaires Ă celles obtenues avec rotation. Pour ce qui est de la gestion de la tempĂ©rature, les rĂ©sultats Ă©taient similaires aux simulations. Cependant, les tempĂ©ratures des parois nâont pu respecter les objectifs, car la tempĂ©rature de croissance a Ă©tĂ© sous-Ă©valuĂ©e. Finalement, ce projet, par le succĂšs du nouveau rĂ©acteur LĂA, pourra influencer lâavenir de lâindustrie de fabrication dans le domaine du vide, des semi-conducteurs et des matĂ©riaux rĂ©fractaires au QuĂ©bec
Wafer-scale detachable monocrystalline Germanium nanomembranes for the growth of III-V materials and substrate reuse
Germanium (Ge) is increasingly used as a substrate for high-performance
optoelectronic, photovoltaic, and electronic devices. These devices are usually
grown on thick and rigid Ge substrates manufactured by classical wafering
techniques. Nanomembranes (NMs) provide an alternative to this approach while
offering wafer-scale lateral dimensions, weight reduction, limitation of waste,
and cost effectiveness. Herein, we introduce the Porous germanium Efficient
Epitaxial LayEr Release (PEELER) process, which consists of the fabrication of
wafer-scale detachable monocrystalline Ge NMs on porous Ge (PGe) and substrate
reuse. We demonstrate monocrystalline Ge NMs with surface roughness below 1 nm
on top of nanoengineered void layer enabling layer detachment. Furthermore,
these Ge NMs exhibit compatibility with the growth of III-V materials.
High-resolution transmission electron microscopy (HRTEM) characterization shows
Ge NMs crystallinity and high-resolution X-ray diffraction (HRXRD) reciprocal
space mapping endorses high-quality GaAs layers. Finally, we demonstrate the
chemical reconditioning process of the Ge substrate, allowing its reuse, to
produce multiple free-standing NMs from a single parent wafer. The PEELER
process significantly reduces the consumption of Ge during the fabrication
process which paves the way for a new generation of low-cost flexible
optoelectronics devices.Comment: 17 pages and 6 figures along with 3 figures in supporting informatio
A novel antiangiogenic and vascular normalization therapy targeted against human CD160 receptor
A monoclonal anti-CD160 antibody inhibits the growth of new vessels in pathological ocular and tumor neoangiogenesis but not in healthy tissues
Rapid response to the M_w 4.9 earthquake of November 11, 2019 in Le Teil, Lower RhĂŽne Valley, France
On November 11, 2019, a Mw 4.9 earthquake hit the region close to Montelimar (lower RhĂŽne Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude, and the moderate to large damages it produced in several villages. InSAR interferograms indicated a shallow rupture about 4 km long reaching the surface and the reactivation of the ancient NE-SW La Rouviere normal fault in reverse faulting in agreement with the present-day E-W compressional tectonics. The peculiarity of this earthquake together with a poor coverage of the epicentral region by permanent seismological and geodetic stations triggered the mobilisation of the French post-seismic unit and the broad French scientific community from various institutions, with the deployment of geophysical instruments (seismological and geodesic stations), geological field surveys, and field evaluation of the intensity of the earthquake. Within 7 days after the mainshock, 47 seismological stations were deployed in the epicentral area to improve the Le Teil aftershocks locations relative to the French permanent seismological network (RESIF), monitor the temporal and spatial evolution of microearthquakes close to the fault plane and temporal evolution of the seismic response of 3 damaged historical buildings, and to study suspected site effects and their influence in the distribution of seismic damage. This seismological dataset, completed by data owned by different institutions, was integrated in a homogeneous archive and distributed through FDSN web services by the RESIF data center. This dataset, together with observations of surface rupture evidences, geologic, geodetic and satellite data, will help to unravel the causes and rupture mechanism of this earthquake, and contribute to account in seismic hazard assessment for earthquakes along the major regional CĂ©venne fault system in a context of present-day compressional tectonics
Altimetry for the future: Building on 25 years of progress
In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ââGreenâ Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instrumentsâ development and satellite missionsâ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion
Altimetry for the future: building on 25 years of progress
In 2018 we celebrated 25âŻyears of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology.
The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the âGreenâ Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instrumentsâ development and satellite missionsâ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion
Suivi d'un site atelier dans le golfe de Fos: une diversité myrmécologique insoupçonnée
International audienc
LargeâScale Formation of Uniform Porous Ge Nanostructures with Tunable Physical Properties
Abstract Porous germanium (PGe) nanostructures attract a lot of attention for various emerging applications due to their unique properties. Consequently, there is an increasing need for the development of lowâcost synthesis routes that are compatible with largeâscale production. Bipolar electrochemical etching (BEE) is a widely used solution for producing porous Ge layers. However, the lack of controllable production of largeâscale uniform PGe layers is the limiting factor for mainstream applications. Largeâscale homogeneous PGe layers formation is demonstrated by improving the BEE process. The PGe structures demonstrate excellent homogeneity in thickness and porosity, with a relative variation of below 2% across the 100 mm wafer. Furthermore, this process enables accurate tuning of the PGe's physical properties through variation of the etching parameters. PGe structures with porosity ranging from 40% to 80% and an adjustable thickness, while preserving low surface roughness are demonstrated, giving access to a large variety of PGe nanostructures for a wide range of applications. Ellipsometry and Xâray reflectivity are employed to measure the porosity and thickness of PGe layers, providing fast and nonâdestructive methods of characterization. These findings lay the groundwork for the largeâscale production of highâquality PGe layers with onâdemand characteristics
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