Accurate strain measurements in highly strained Ge microbridges

Ge under high strain is predicted to become a direct bandgap semiconductor. Very large deformations can be introduced using microbridge devices. However, at the microscale, strain values are commonly deduced from Raman spectroscopy using empirical linear models only established up to 1.2% for uniaxial stress. In this work, we calibrate the Raman-strain relation at higher strain using synchrotron based microdiffraction. The Ge microbridges show unprecedented high tensile strain up to 4.9 % corresponding to an unexpected 9.9 cm-1 Raman shift. We demonstrate experimentally and theoretically that the Raman strain relation is not linear and we provide a more accurate expression.Comment: 10 pages, 4 figure

Disproportionate Alterations in the Anterior and Posterior Insular Cortices in Obsessive–Compulsive Disorder

Recent studies have reported that the insular cortex is involved in the pathophysiology of obsessive–compulsive disorder (OCD). However, specific morphometric abnormalities of the insular subregions remain unclear. In this study, we examined insular cortical volume to determine whether the volume of the anterior and posterior insular cortices of unmedicated OCD patients differed according to different symptom dimensions.Using magnetic resonance imaging, we measured the gray matter volumes of the insular cortex and its subregions (anterior and posterior divisions) in 41 patients with OCD (31 drug-naïve and 10 non-medicated) and 53 healthy controls. Volumetric measures of the insular cortex were compared according to different OC symptoms. Enlarged anterior and reduced posterior insular cortices were observed in OCD patients. The insular volumetric alterations were more significant in OCD patients with predominant checking rather than cleaning symptoms when compared with healthy controls.Our results suggest the presence of unbalanced anterior and posterior insular volumetric abnormalities in unmedicated OCD patients and emphasize the distinct role of the insular cortex in different OC symptoms. We propose that the insular morphometric alterations may influence the modulation of interoceptive processing, the insular functional role, in OCD patients with different symptoms

Matière organique et pollution par les hydrocarbures dans les sédiments superficiels du golfe d'Arzew (mer Méditerranée, Algérie)

The distribution of global organic parameters (organic carbon, nitrogen, hydrolyzable carbon) was established in surficial sediments of the Gulf of Arzew. Moreover, humic substances, humin and hydrocarbons have provided information on the organic matter origin and evolution in the identified sedimentary areas: prodeltas at the mouth of the dry rivers Cheliff and Macta; muddy mid-deposits and carbonated shallow environments. The higher organic matter concentrations characterize the muddy mid-deposits and especially the western part located near the Arzew and Bethioua harbours (TOC > 0.9 %; Nt = 0.35 % d.w.). The marine origin of the organic matter is supported by low C/N ratios (5-9) in the total sediments and the position in the Van Krevelen diagram of the humic acid H/C, N/C and O/C atomic ratios. The predominant marine character results from an important phytoplanktonic production. Only organic matter of the Cheliff prodelta is characterized by a double marine and continental signal. The degradation state of organic matter shows that the compounds are more degraded in the western part of the gulf, towards the east to west transfer of matter. The Arzew and Bethioua harbours areas are enriched in hydrocarbons (90-180 mg kg(-1)) according to the N.S.A. norm (1975) and represent significant petrogenic pollution levels.La distribution des concentrations des paramètres organiques globaux (carbone organique, azote, carbone hydrolysable) a été établie pour l'ensemble des sédiments superficiels du golfe d'Arzew. L'étude des substances humiques, de l'humine et des hydrocarbures a permis de définir l'origine et le degré d'évolution de la matière organique dans les principales unités sédimentaires identifiées : zones prodeltaïques au droit des embouchures des principaux oueds (Chéliff et Macta), vasière centrale et hauts fonds carbonatés. La grande vasière située au centre du golfe est enrichie en matière organique ainsi que les zones portuaires d'Arzew et Béthioua (Corg > 0,9 % ; Nt = 0,35 % p.s.). Les rapports Full-size image (<1 K) des dépôts sont bas, compris entre 5 et 9 et correspondent à l'origine marine du matériel organique. L'analyse élémentaire des acides humiques montre, sur le diagramme de Van Krevelen (rapports atomiques Full-size image (<1 K), Full-size image (<1 K) et Full-size image (<1 K)), leur appartenance au domaine marin. Cette origine marine résulte d'une importante production phytoplanctonique dans le golfe. Néanmoins, on note une exception au large de l'embouchure de l'oued Chéliff, où la matière organique présente un caractère à la fois marin et continental. L'observation du degré d'évolution de la matière organique montre que celle-ci est plus évoluée dans la partie occidentale du golfe, dans le sens du transfert de matière de l'est vers l'ouest. Les zones portuaires de Béthioua et d'Arzew se sont révélées enrichies en hydrocarbures (90–180 mg kg−1) par rapport aux normes établies par la N.A.S. (1975), indice d'une pollution pétrogénique significative

Impact of the growth strategy and device fabrication on the alloy homogeneity in optoelectronic grade Sn-rich GeSn

International audienceHigh Sn-content Ge1-xSnx alloys are excellent candidates for the fabrication of electronic and optoelectronic monolithically integrated devices on CMOS platforms. The fabrication of high performance devices requires high quality GeSn layers free of Sn precipitates. This work reports on the characterization of GeSn layers and micro-disk lasers with Sn concentrations ranging from 6 to 16% using synchrotron nano X-ray fluorescence mapping and nano X-ray absorption spectroscopy techniques. We demonstrate that the Sn precipitation observed in thick GeSn layers grown directly on Ge buffers can be fully suppressed, for Sn concentrations as high as 16%, with Ge1-xSnx step-graded buffers. The combination of optimal micro-disk fabrication parameters and full suppression of Sn precipitation can explain the superior lasing performance obtained in micro-disk lasers fabricated using such stacks

Electronic properties of gold catalyst silicon nanowires by photoluminescence: the role of the surface.

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