Étude fondamentale des interactions plasma-graphène dans les plasmas Argon/B2H6

Les travaux de recherche menés dans cette thèse de doctorat se sont focalisés sur la compréhension des interactions graphène-plasma dans le cas de l’exposition de graphène polycristallin à un plasma d’argon pouvant contenant du diborane (B2H6). Une attention particulière est portée sur la cinétique de génération de dommage dans un plasma d’argon pur. Ainsi dans le cas d’un plasma continu, l’absence de seuil en énergie pour la génération de dommage due à un bombardement ionique est mis en évidence. Ceci ne peut s’expliquer que par une gravure à deux étapes, facilitée par la densité ionique élevée caractéristique des plasmas inductifs opérés en mode H. La caractérisation Raman des échantillons exposés au plasma montre une large distribution sur la petite zone sondée. Afin de relier ces fluctuations à l’état initial du graphène, l’imagerie Raman (RIMA) est adaptée dans le but d’extraire des données quantitatives sur l’état du graphène et utilisée pour le reste des travaux. Par la suite, l’étude temporelle des plasmas pulsés en puissance permet de trouver des conditions opératoires avec une fluence ionique drastiquement diminuée. Les traitements subséquents combinés aux analyses RIMA ont permis de suivre l’évolution de l’état du graphène et de distinguer l’état des joints du graphène des domaines de croissance. Ainsi, pour la première fois, l’autoréparation des joints de grains dans un matériau 2D est mis en évidence expérimentalement. Cet effet, théorisé dans les matériaux 3D mais difficilement observé expérimentalement, était effectivement prédis dans le cas du graphène. De plus, un contrôle fin des conditions opératoires du plasma pulsé d’argon a permis d’extraire des paramètres plasmas dans lesquels les métastables d’argons puis les photons VUV émis par les états résonants de l’argon sont les principaux vecteurs d’énergie. Suivant la même méthodologie que précédemment, ces traitements ont mis en lumière les rôles respectifs des ions, des métastables et des photons VUV dans la transmission d’énergie du graphène. Enfin, l’introduction de 5% de diborane a pour conséquence une modification radicale des paramètres physique du plasma. L’exposition de graphène à ce graphène à ce plasma démontre l’intérêt de cette technique pour l’incorporation élevé de bore tout en minimisant la génération de dommagesThe research realized in this PhD thesis focuses on the understanding of plasma-graphene interactions during exposure of polycrystalline graphene films to a low-pressure argon RF plasma containing diborane (B2H6). A particular attention is devoted to the kinetics driving the damage formation dynamics. In the case of a continuous, argon plasma, the absence of energy threshold for the production of ion-induced damage is demonstrated. This is explained by two-step etching, facilitated by the high number density of charged species in the H-mode of RF plasmas. Raman characterization of plasma-treated graphene films shows a wide distribution over the small area surveyed. In order to link these fluctuations to the initial state of graphene, Raman imaging (RIMA) is adapted to extract quantitative data on the state of graphene before and after plasma treatment. Subsequently, the temporal study of argon RF plasmas in the pulsed regime makes it possible to find operating conditions with a drastically reduced fluence of charged species compared to the continuous regime; in combination with RIMA studies, this allows temporally- and spatially-resolved investigations of plasma-graphene interactions. For the first time, a preferential self-healing of ion-irradiation damage at grain boundaries of graphene films is experimentally demonstrated. Moreover, by using several electrical and optical diagnostics of the argon plasma in the pulsed regime, it is possible to determine operating conditions in which either the ions, the metastables or the VUV photons emitted by the resonant states become the main energy vectors. From these experiments, the respective roles of each of these species in the physics of plasma-graphene interactions could be highlighted. Finally, the introduction of 5% of diborane into the argon plasma induces a radical modification of the physicochemical properties of the plasma. Exposure of graphene films to this highly reactive plasma reveals high boron incorporation with minimal ion and hydrogen damage

Convergence de faciés et pléoenvironnements dans les bassins sédimentaires du Permien supérieur de l'Argentera -Barrot et de Provence orientale

Mémoire HS n° 13 - Géologie Alpine : Le détritisme dans le Sud-Est de la France - Colloque Association des Géologues du Sud-est - Grenoble 11-12 décembre 1986Les series permiennes du Sud Est de la France présentent une forte convergence de faciès lithologiques, associée à une convergence des processus de mise en place. La série stratigraphique du Barrot est choisie pour décrire les trois faciès principaux que l'on observe dans le Permien: faciès silto-argileux des formations du Cians et de la Roudoule (éoliens et lacustres), faciès conglomératiques et gréseux de la formation de Léouvé (coulées boueuses et dépôts fluviatiles). Différents degrés d'analogie peuvent être établis avec les ensembles permiens de l'Argentera et de Provence orientale où des milieux de dépôts similaires donnent des faciès voisins, modulés par des facteurs locaux. Le climat et la tectonique sont les facteurs dominants de la sédimentation. Ils agissent en tant que facteurs d'uniformisation et de différenciation . Le climat, chaud et semi-aride, à périodes sèches et humides alternées, induit des faciès très contrastés tels que les coulées boueuses, très grossières, ou des sédiments très fins, éoliens ,et lacustres . Le régime géodynamique distensif crée des grabens asymétriques et le soulèvement des marges alimente irrégulièrement les bassins subsidents. La dimension des bassins et l'activité différentielle des marges régissent la distribution des corps sédimentaires et modulent la rapidité du comblement

Apports du radar géologique à l'étude de la dynamique sédimentaire à l'Holocène récent dans la plaine interdunaire de Merlimont (Pas-de-Calais).

International audienceA Ground Penetrating Radar (GPR) survey was carried out on the Pas-de-Calais coast in arder la quantify the evolution of sand dunes during the holocene period. 15 km of GPR profiles were recorded with 100 and 500 MHz antennae. Some boreholes were drilled to control the GPR results. Correlation between GPR and boreholes is better than 35 cm. At last, 7 peat layers have been found wilh a north-east dip. It reveals the existence of changes in hydrogeological conditions (variations of water table) during the last 900 years (mast ancient peat in dunes peat layers). Moreover, some ancient dunes features have been outlined between flat peat layers. GPR is a robust tool for sedimentological interpretation in sandy context

External irradiation models for intracranial 9L glioma studies

<p>Abstract</p> <p>Purpose</p> <p>Radiotherapy has been shown to be an effective for the treatment human glioma and consists of 30 fractions of 2 Gy each for 6-7 weeks in the tumor volume with margins. However. in preclinical studies, many different radiation schedules are used. The main purpose of this work was to review the relevant literature and to propose an external whole-brain irradiation (WBI) protocol for a rat 9L glioma model.</p> <p>Materials and methods</p> <p>9L cells were implanted in the striatum of twenty 344-Fisher rats to induce a brain tumor. On day 8, animals were randomized in two groups: an untreated group and an irradiated group with three fractions of 6 Gy at day 8, 11 and 14. Survival and toxicity were assessed.</p> <p>Results</p> <p>Irradiated rats had significantly a longer survival (p = 0.01). No deaths occurred due to the treatment. Toxicities of reduced weight and alopecia were increased during the radiation period but no serious morbidity or mortality was observed. Moreover, abnormalities disappeared the week following the end of the therapeutic schedule.</p> <p>Conclusions</p> <p>Delivering 18 Gy in 3 fractions of 6 Gy every 3 days, with mild anaesthesia, is safe, easy to reproduce and allows for standardisation in preclinical studies of different treatment regimens glioma rat model.</p

Atteinte pulmonaire sévère au cours de la neurofibromatose de type 1

Type 1 neurofibromatosis (NF1) is a hereditary disease inherited as an autosomal dominant. Respiratory involvement is rare. We report the case of a woman suffering from NF1 with mutation of the corresponding gene and with respiratory involvement combining diffuse parenchymatous lesions, severe precapillary pulmonary hypertension and an enlarging, spiculated pulmonary nodule, very suspicious of malignancy, though histological examination was not possible on account of the patient\u27s poor respiratory function. There was progressive deterioration of the patient\u27s respiratory condition, leading to death, despite the introduction of oral therapy combining a phosphodiesterase 5 inhibitor and an endothelin receptor antagonist. Our case illustrates the development of multiple severe respiratory pathologies in the setting of NF1. The specific contribution of the NF1 gene mutation in the pathophysiology of these different pulmonary manifestations needs to be examined in detail

Multi-risk approach in centralized and decentralized risk governance systems: Case studies of Naples, Italy and Guadeloupe, France

Recent multi-hazard disasters, such as 2004 Sumatra-Andaman earthquake and tsunami, 2011 Tohoku earthquake, tsunami and nuclear catastrophe and 2013 Super Typhoon Haiyan, showed the need for a multi-risk approach, which takes into consideration multiple risks and interdependencies between them. The first attempts to provide assessment of natural hazards based on multi-risk approach (MRA) exist in science. Also at the level of the European policy-making process, several strategic guidelines were developed to address multi-risk issues. However, MRA is more than assessment of risks for a given territory, it also includes the processes of knowledge transfer from science to policy and implementation of risk mitigation measures in frames of existing governance systems. The European Union is characterized by the multiple levels of governance and variety of risk governance systems, marked by different degree of centralization and decentralization of the decision-and policy-making processes. In this paper we present some results about the impacts of decentralization or centralization on implementation of MRA, with a focus on two case studies, Naples (Italy) and Guadeloupe (France). The methodology of research included several rounds of interactions with stakeholders from practice, such as interviews, workshops, and round table discussions. The results show that both governance systems have their own strengths and weaknesses. Elements of decentralized governance can favour creation of local multi-risk commissions and elements of centralized governance can lead to improvement of interagency communication and creation of inter-agency environment. However, both governance systems suffer from such deficiencies as lack of financial, technical, and institutional capacities at local level. Further research is needed to understand how implementation of MRA can be strengthened through multi-risk platforms. However, MRA cannot be a subsidiary to a single risk approach and both approaches have to be pursued

Electron correlation in the Si(100) surface

Motivated by the controversy between quantum chemists and solid-state physicists, and by recent experimental results, spin-polarized density-functional (DFT) calculations are used to probe electron correlation in the Si(100) reconstructed surface. The ground state displays antiferromagnetic spin polarization for low dimer inclinations indicating, not magnetic order, but the importance of Mott-like correlations among dangling bonds. The lowest energy corresponds to a higher dimer inclination with no spin. DFT energies, however, should be taken with caution here. Our results together with quantum-chemical findings suggest dimers with highly correlated electrons that tend to buckle due to interactions with other dimers.Comment: 5 pages, 1 eps figure, 1 table; RevTeX v3.1. To appear in Surface Science (proceedings of the European Conference On Surface Science, ECOSS-19, Madrid, Sept. 5-8, 2000