Electrostatically-Driven Resonator on Soi with Improved Temperature Stability

This paper deals with a single-crystal-silicon (SCS) MEMS resonator with improved temperature stability. While simulations have shown that the temperature coefficient of resonant frequency can be down to 1 ppm/degrees C, preliminary measurements on non-optimised structures gave evidence of a temperature coefficient of 29 ppm/degrees C. Design, optimisation, experimental results with post process simulation and prospective work are presented.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Neuropilin-1 Controls Endothelial Homeostasis by Regulating Mitochondrial Function and Iron-Dependent Oxidative Stress.

The transmembrane protein neuropilin-1 (NRP1) promotes vascular endothelial growth factor (VEGF) and extracellular matrix signaling in endothelial cells (ECs). Although it is established that NRP1 is essential for angiogenesis, little is known about its role in EC homeostasis. Here, we report that NRP1 promotes mitochondrial function in ECs by preventing iron accumulation and iron-induced oxidative stress through a VEGF-independent mechanism in non-angiogenic ECs. Furthermore, NRP1-deficient ECs have reduced growth and show the hallmarks of cellular senescence. We show that a subcellular pool of NRP1 localizes in mitochondria and interacts with the mitochondrial transporter ATP-binding cassette B8 (ABCB8). NRP1 loss reduces ABCB8 levels, resulting in iron accumulation, iron-induced mitochondrial superoxide production, and iron-dependent EC senescence. Treatment of NRP1-deficient ECs with the mitochondria-targeted antioxidant compound mitoTEMPO or with the iron chelator deferoxamine restores mitochondrial activity, inhibits superoxide production, and protects from cellular senescence. This finding identifies an unexpected role of NRP1 in EC homeostasis

X-ray multilayer monochromator with enhanced performance

International audienceAn x-ray multilayer monochromator with improved resolution and a low specular background is presented. The monochromator consists of a lamellar multilayer amplitude grating with appropriate parameters used at the zeroth diffraction order. The device is fabricated by means of combining deposition of thin films on a nanometer scale, UV lithography, and reactive ion etching. The performance of this new monochromator at photon energies near 1500 eV is shown

Croissance de Si3N4 sur GaAs et InP par pulvérisation réactive par faisceau d'ions

Auger electron spectrometry is used to study chemical preparation and ion etching of InP and then the growth mode and the masking properties of Si 3N4 deposited by reactive ion beam sputtering on GaAs and InP. Preferential sputtering of phosphorus during InP ion cleaning is evidenced by a 30 % decrease of P/In when the ion energy is varied from 90 eV to 500 eV. Examination of Auger peaks of gallium and arsenic for GaAs and of indium for InP during Si3N4 deposition shows an alteration of the substrate surface composition at the very beginning of the deposition. Some possible mechanisms are proposed to explain the observed behaviors. A few monolayers of Si3N4 are sufficient to obtain a thermal stabilization of the GaAs surface but only limit partially indium diffusion in the case of InP.La spectrométrie Auger est utilisée pour étudier la préparation chimique et le nettoyage ionique de substrats d'InP puis le mode de croissance et les propriétés d'encapsulation de Si3N4 déposé par pulvérisation ionique réactive sur GaAs et InP. La pulvérisation préférentielle du phosphore lors d'un décapage ionique est mise en évidence par une décroissance de 30 % du rapport P/In lorsque l'on fait varier l'énergie des ions de 90 eV à 500 eV. L'observation des pics Auger de l'arsenic et du gallium pour GaAs et de l'indium pour InP lors du dépôt de Si3N4 indique une altération de la composition de surface du substrat au début de la croissance du nitrure. Des mécanismes sont proposés pour rendre compte des comportements constatés. Quelques monocouches de Si3N4 suffisent pour stabiliser en température la surface de GaAs mais limitent seulement partiellement la diffusion de l'indium dans le cas de InP

Effect of the residual stress on the determination through nanoindentation technique of the Young's modulus of W thin film deposit on Si02/Si substrate

International audienc

High current densities in copper microcoils : influence of substrate on failure mode

Copper planar microcoils were processed by U.V. lithography on SiO2/Si and Kapton®. The coils were packaged on different supports in order to create varying thermal exchange conditions. The electric current was increased step by step until the electric connection breaks, the microcoils remaining free on a thermal point of view. The copper temperature was estimated from its resistivity. It allowed to show that the thermal exchange mode of the wire-bonded microcoils is conductive. The current density was calculated taking into account the deterioration of the coils by oxidation. Its maximum value is linearly decreasing with the thermal exchange ability of the support. The failure modes of the microcoils are related to track melting and oxidation, the current density remaining one order too weak to induce electromigration