Detection limit of phosphorus in diamond by high mass resolution secondary ion mass spectrometry (HMR‐SIMS)

International audienceIn diamond, Secondary Ion Mass Spectrometry (SIMS) is usually performed in order to detect and measure the depth distribution of impurities. The SIMS measurements are then performed by using parameters allowing high sensitivities. In the classical configuration for diamond analysis, the mass resolution is usually set at the lowest value and gives access to the concentration of most dopants. In the case of phosphorus, the detection limit is then in the range of a few 10 15 at/cm 3 (~20 ppb). In this work, we study several diamond samples and focus the SIMS detection on the secondary ions of masses 12 (carbon) and 31 (phosphorus). We show that SIMS analyses require high mass resolution (HMR) to accurately separate unexpected molecular ions detected at 31 a.m.u.. In such HMR-SIMS analyses, we improve the detection limit of phosphorus by one decade and achieve the value of 3x10 14 at/cm 3

Trajectoire et profil gériatrique des patients âgés de 75 ans et plus appelant le SAMU-centre 15 (étude rétrospective de 692 appels à la régulation médicale du SAMU 69 et analyse des patients envoyés aux urgences)

Le Service d'Aide Médicale d'Urgence se doit d'apporter une réponse rapide et adaptée aux besoins de soins urgents des patients. Avec l'augmentation de l'espérance de vie et des maladies à risques de décompensation, le recours des personnes âgées au SAMU s'accroît. Face à la complexité de la régulation de cette population, l'envoi dans des Services d'Accueil des Urgences est parfois la seule alternative. Pourtant il est inapproprié à la prise en charge de soins non urgents. L'objectif principal de cette étude est de décrire le profil gériatrique et la trajectoire des patients de 75 ans et plus depuis l'appel au centre 15 jusqu'à leur orientation au décours des urgences à travers l'écoute d'appels les concernant à la régulation du SAMU. Une étude descriptive réalisée au SAMU-Centre 15 du Rhône a été réalisée, reposant sur l'écoute rétrospective d'appels sur 7 jours randomisés entre le 01/04/2012 et le 31/03/2013. Tous les patients de 75 ans et plus étaient inclus. Les données gériatriques nécessaires à la régulation, définies par un consensus d'expert, ont été recueillies. Concernant les patients adressés aux urgences, la durée de leur passage, la CCMU et leur orientation à l'issue du séjour étaient recherchés. Sur les 4168 appels, 17.1% concernaient des sujets de 75 ans et plus. L'âge moyen des 692 patients inclus était de 85 +- 6 ans. Ils étaient régulés par un médecin hospitalier (30,5%), un médecin libéral ( 48,5%) ou l'infirmier coordonnant les opérations-pompiers (21%). Les items permettant une évaluation gériatrique à minima étaient renseignés dans 10% des appels. Les patients vivaient en établissement surveillé dans 14,9% des cas. A la fin de la régulation, 426 patients (61,6%) étaient adressés aux urgences et 242 patients restaient à domicile. Les facteurs indépendants prédisposant l'envoi aux urgences étaient: le motif traumatologique, la résidence en établissement surveillé et l'appel entre 8h et 18h. La durée de leur passage au SAU variait de 13 minutes à 23h06 pour une médiane de 4h34 [2h37; 6h58]. L'état clinique de 73,1% des patients était considéré stable (CCMU 1 ou 2). Le pronostic vital de 4,5% des sujets était engagé (CCMU 4 ou 5). Près de 30% des patients adressés par le SAMU consultaient le SAU suite à une chute. A l'issue des urgences, 226 patients étaient hospitalisés dont 94 à l'UHCD. Les patients régulés pour un motif médical et ceux prenant plus de 3 médicaments avaient un risque accru et indépendant, dès la régulation, d'être hospitalisé au décours des urgences. Sur l'ensemble des patients âgés appelant le centre-15, 8,3% étaient admis dans des structures de soins intensifs, 18,3% dans un service de médecine, 5,0% dans un service de chirurgie et 7,6% dans un service de gériatrie. Le SAMU-centre 15 peut s'inscrire en tant qu'élément de la filière gériatrique en limitant les envois inappropriés au SAU. Une ligne téléphonique directe entre les interlocuteurs, un outil d'aide à la régulation gériatrique ou la présence d'un gériatre au centre 15 sont des pistes envisageables. En améliorant la coordination ville-hôpital, ces mesures permettront d'optimiser la trajectoire de soin des personnes âgées et de réduire les dépenses de santéLYON1-BU Santé (693882101) / SudocSudocFranceF

Nitrogen investigation by SIMS in two wide band-gap semiconductors: Diamond and Silicon Carbide

International audienceDiamond and Silicon Carbide (SiC) are promising wide band-gap semiconductors for power electronics, SiC being more mature especially in term of large wafer size (that has reached 200 mm quite recently). Nitrogen impurities are often used in both materials for different purpose: increase the diamond growth rate or induce n-type conductivity in SiC. The determination of the nitrogen content by secondary ion mass spectrometry (SIMS) is a difficult task mainly because nitrogen is an atmospheric element for which direct monitoring of N ions give no or a weak signal. With our standard diamond SIMS conditions, we investigate 12C14N-secondary ions under cesium primary ions by applying high mass resolution settings. Nitrogen depthprofiling of diamond and SiC (multi-) layers is then possible over several micrometer thick over reasonable time analysis duration. In a simple way and without notably modifying our usual analysis process, we found a nitrogen detection limit of 2x10 17 at/cm 3 in diamond and 5x10 15 at/cm 3 in SiC

First Study of Manganese Diffusion in Cr2O3, polycrystals and thin films, by SIMS

International audienceChromia layers are formed on many industrial alloys and act as a protective barrier against the corrosion of the materials by limiting the diffusion of oxygen and cations. Most of these alloys contain manganese as an impurity, and manganese oxides are often found at the outer surface of the oxide films. In order to clarify the oxidation mechanism and to check if chromia acts as a barrier, manganese diffusion in chromia was studied in both polycrystals and oxide films formed by oxidation of Ni-30Cr alloy in the temperature range 700-1100°C at an oxygen pressure of 10-4 atm. After deposition of Mn on the chromia surface and a diffusing treatment, the manganese penetration profiles were established by secondary ion mass spectrometry. In all cases, the diffusion profiles showed two domains. From the first domain, using the solution of the Fick law for diffusion from a thick film into a semi-infinite medium, bulk diffusion coefficients were determined. With the second domain, Le Claire model allowed the grain boundary diffusion parameter (αDgbδ) to be obtained. Manganese diffusion does not vary significantly according to the nature and microstructure of chromia. The activation energy of grain boundary diffusion is not far from that obtained for bulk diffusion, probably on account of segregation phenomena. Manganese diffusion was compared to cationic self-diffusion and iron diffusion, and related to the protective character of chromia

Nitrogen investigation by SIMS in two wide band-gap semiconductors: Diamond and Silicon Carbide

International audienceDiamond and Silicon Carbide (SiC) are promising wide band-gap semiconductors for power electronics, SiC being more mature especially in term of large wafer size (that has reached 200 mm quite recently). Nitrogen impurities are often used in both materials for different purpose: increase the diamond growth rate or induce n-type conductivity in SiC. The determination of the nitrogen content by secondary ion mass spectrometry (SIMS) is a difficult task mainly because nitrogen is an atmospheric element for which direct monitoring of N ions give no or a weak signal. With our standard diamond SIMS conditions, we investigate 12C14N-secondary ions under cesium primary ions by applying high mass resolution settings. Nitrogen depthprofiling of diamond and SiC (multi-) layers is then possible over several micrometer thick over reasonable time analysis duration. In a simple way and without notably modifying our usual analysis process, we found a nitrogen detection limit of 2x10 17 at/cm 3 in diamond and 5x10 15 at/cm 3 in SiC

Texture effect of neodymium doped gallium oxide thin films on their optical properties

International audienceNeodymium doped b-Ga 2 O 3 films were elaborated on (1 0 0) silicon and (0 0 0 1) sapphire substrates by the radiofrequency magnetron sputtering method. X-ray diffraction, transmission electron microscopy, spectroscopic ellipsometry and photoluminescence measurements were performed to characterize and compare layers elaborated on the two substrates. Also, the Nd content effects were investigated. Films prepared on sapphire substrates were found to form a close orientation relationship with the substrate (À2 0 1) b-Ga 2 O 3 || (0 0 0 1) sapphire, whatever the Nd content in the matrix. By contrast, the films grown on silicon substrates lose this texture for high Nd concentrations with a concomitant decrease of the Nd ions luminescence

Fully self-consistent calculations of momentum distributions of annihilating electron-positron pairs in SiC

International audienceWe performed calculations of momentum distributions of annihilating electron-positron pairs in various fully relaxed vacancy defects in SiC. We used self-consistent two-component density functional theory schemes to find the electronic and positronic densities and wave functions in the considered systems. Using the one-dimensional momentum distributions (Doppler-broadened annihilation radiation line shapes) we calculated the line-shape parameters S and W. We emphasize the effect of the experimental resolution and the choice of the integration ranges for the S and W parameters on the distributions of the points corresponding to different defects in the S(W) plot. We performed calculation for two polytypes of SiC, 3C, and 6H and showed that for silicon vacancies and clusters containing this defect there were no significant differences between the Doppler spectra. The results of the Doppler spectra calculations were compared with experimental data obtained for n-type 6H-SiC samples irradiated with 4-MeV Au ions. We observed a good general agreement between the measured and calculated point

First study of manganese diffusion in Cr2O3 polycrystals and thin films by SIMS

International audienceChromia layers are formed on many industrial alloys and act as a protective barrier against the corrosion of the materials by limiting the diffusion of oxygen and cations. Most of these alloys contain manganese as an impurity, and manganese oxides are often found at the outer surface of the oxide films. In order to clarify the oxidation mechanism and to check if chromia acts as a barrier, manganese diffusion in chromia was studied in both polycrystals and oxide films formed by oxidation of Ni–30Cr alloy in the temperature range 700–1100C at an oxygen pressure of 104 atm. After deposition of Mn on the chromia surface and a diffusing treatment, the manganese penetration profiles were established by secondary ion mass spectrometry. In all cases, the diffusion profiles showed two domains. For the first domain, using the solution of Fick's law for diffusion from a thick film into a semi-infinite medium, bulk diffusion coefficients were determined. For the second domain, the Le Claire model allowed the grain boundary diffusion parameter (Dgb) to be obtained. Manganese diffusion does not vary significantly according to the nature and microstructure of chromia. The activation energy of grain boundary diffusion is not far from that obtained for bulk diffusion, probably on account of segregation phenomena. Manganese diffusion was compared to cationic self-diffusion and iron diffusion, and related to the protective character of chromia

Impurity diffusion of cerium and gadolinium in single- and polycrystalline yttria-stabilized zirconia

International audienceYttria-stabilized zirconia (YSZ) ceramic is considered as an attractive material for solid oxide fuel cells or for nuclear applications such as inert matrix for the destruction of excess plutonium and host material for nuclear waste storage. Long term properties as phase stability depend on cation diffusion. Therefore, the present work is focused on the diffusion study of Ce and Gd in YSZ single crystals and high density polycrystals. A thin film of Ce or Gd was deposited either by spin-coating method or by physical vapour deposition on the surface of polished samples. The diffusion experiments were performed from 1173 to 1673 K under air. The Ce or Gd diffusion profiles were determined by secondary ion mass spectrometry. The analysis of the penetration profiles led to the determination of bulk diffusion (Db) in single crystals and effective (Deff), bulk and grain boundary diffusion coefficients (Dgb) were determined in polycrystals. The dependence of diffusion coefficients on temperature is described by means of Arrhenius equations and the diffusivity is compared with literature