Innovations en microfabrication pour la production de circuits à très hautes fréquences et ajustables

RÉSUMÉ Au cours des dernières années, deux tendances importantes dans le domaine des micro-ondes ont été l’augmentation de la fréquence d’opération et l’intégration de plusieurs fonctionnalités dans un même dispositif. Ces changements ont généré des défis nouveaux, principalement liés à l’utilisation d’éléments ajustables intégrés et à la difficulté de fabrication de circuits dont les dimensions critiques sont très fines. Deux pistes de solution sont présentées dans cette thèse : le recours à des éléments ajustables à base de matériaux ferroélectriques intégrés au substrat et l’utilisation d’un procédé de fabrication innovateur à base de pâtes photoimageables mises en forme en couches épaisses pour la fabrication de circuits en trois dimensions. Le matériau ferroélectrique choisi est le titanate de baryum et strontium, noté BaxSr1-xTiO3, ou plus simplement BST. Comme tous les ferroélectriques, sa permittivité varie en fonction d’un champ électrique externe appliqué. Pour déposer ce matériau, la pulvérisation RF est utilisée. L’analyse par diffraction rayons X confirme la nature cristalline des couches minces de BST, alors qu’une mesure par rétrodiffusion de Rutherford semble indiquer une légère déviation par rapport à la stœchiométrie prévue. Une lacune en titane est identifiée comme étant la source probable de cette variation. En ajoutant du titane comme dopant diffusé dans la couche de BST, ses propriétés électriques se trouvent améliorées pour des concentrations de titane excédentaire de 2-5 % en volume. Les couches minces de BST optimisées présentent une ajustabilité de 35 % sous un potentiel de 20 V. Pour réaliser ces mesures, des condensateurs à plaques parallèles sont utilisés. La dépendance de la tangente des pertes en fonction du champ appliqué est aussi mise en évidence. Une fois les couches minces de BST suffisamment performantes, un déphaseur variable est conçu et fabriqué. Ce déphaseur prend la forme d’un filtre passe-bas en technologie de guides coplanaires chargé de condensateurs ajustables en parallèle. Le déphaseur variable présente une figure de mérite de 36 º/dB avec un potentiel d’activation de 20 V, ce qui le place en milieu de peloton pour la figure de mérite, mais parmi les premiers pour le potentiel utilisé. Toutefois, un grand déplacement de la fréquence d’opération indique que les propriétés électriques du BST changent en variant l’épaisseur du dépôt. Les pâtes photoimageables permettent des résolutions latérales d’environ 20 µm et des épaisseurs du même ordre.----------ABSTRACT In recent years, the microwave field has seen two important trends: the increase in the operation frequency and the integration of several functions in one device. These changes have brought new challenges, mainly related to the use of integrated tunable elements and fabrication problems caused by the increasingly small critical dimensions required for high frequency operation. Two possible solutions are presented in this thesis: the use of ferroelectric-based adjustable elements integrated onto the substrate and the fabrication of three dimensional circuits using an innovative manufacturing process called photoimageable thick films. The ferroelectric material chosen is barium and strontium titanate noted BaxSr1-xTiO3, or simply BST. As all ferroelectrics, its permittivity can be changed by applying an external electric field. RF sputtering is used to deposit this material. X-ray diffraction analysis confirms the crystalline nature of the BST thin films while a measurement by Rutherford backscattering spectroscopy suggests a slight deviation from the expected stoichiometry. A titanium deficiency is identified as the likely source of this variation. The addition of titanium as a dopant diffused into the BST film is shown to have important impact on its electrical properties. Optimum concentration of titanium dopant is determined to be 2-5% by volume. The optimized BST thin films have an adjustability of 35% with a potential of 20 V. To achieve these measures, parallel plate capacitors are used. The dependence of the tangent loss as a function of the applied field is also highlighted. Once BST thin films demonstrate satisfactory performances, a variable phase shifter is designed and fabricated. This phase shifter is implemented as a low-pass filter in coplanar guides technology loaded with adjustable capacitors. The variable phase shifter has a figure of merit of 36 °/dB with an activation potential of 20 V, which places it in the midfield for the figure of merit, but among the first for the small potential used. However, a large shift in the operating frequency indicates that the electrical properties of BST are thickness dependant. Photoimageable pastes allow lateral resolutions of about 20 microns and thicknesses of the same order. Since this process is multi-layered in nature, it is suitable for the realization of millimeter wave circuits of complex geometry, such as waveguides. This approach has been explored by only one research group to this day. However, these materials were not designed for use with high frequency, so it is necessary to characterize their microwave properties

Synthèse et caractérisation de nouveaux complexes carboxylates de zirconium(IV)

Largement étudiés en reconnaissance moléculaire, catalyse et relargage de médicaments, les cavitants sont des assemblages supramoléculaires synthétiques très prometteurs dans le domaine de la chimie hôte-invité. Ces macromolécules aux caractéristiques uniques peuvent bénéficier de l’auto-assemblage des métaux de transition avec des ligands rigides pour former ce que l’on appelle les métallocavitants. Les métallocavitants de boronate de tantale, dotés de sites actifs acides de Lewis, ont prouvé leur pertinence dans ce domaine. Des études structurelles et électroniques ont permis la synthèse de métallocavitants à cavité élargie et électrophile. Dans le but d’élargir la visibilité de ce type de métallocavitant, on cherche à créer une cavité moins électropositive. Sachant que les ligands boronates et les atomes de tantale sont responsables de l’électropositivité de la cavité, ces fragments sont remplacés par les carboxylates et le zirconium. De nouveaux complexes organométalliques démontrant d’intéressantes propriétés supramoléculaires ont été synthétisés

Case Report of a Remote Ischemic Preconditioning Intervention during Aerobic Exercise in a 44-year-old Amateur Triathlete Male with a History of Acute Myocardial Infarction

International Journal of Exercise Science 13(3): 924-937, 2020. Over the years, exercise has become increasingly important in patients with acute myocardial infarction (AMI). However, AMI patients need to be closely monitored since they maintain cardiovascular disease risks, such as ventricular repolarization abnormalities in electrocardiograms during exercise and rest. A recent study showed the need to focus on the different potential mechanisms and the applicability of remote ischemic preconditioning (RIPC) for cardiac patients engaged in exercise rehabilitation. This is the first case report that explores the effectiveness of an RIPC intervention in a 44-year-old amateur triathlete male with a history of AMI during a moderate (75% of gas exchange threshold) and high (115% of gas exchange threshold) intensity steady-state cycling aerobic exercise. Prior to aerobic exercise, the participant was allocated to either RIPC intervention or CTL (control) with four cycles of five minutes of ischemia followed by five minutes of reperfusion. ECG was continuously recorded during the protocol. These findings showed that RIPC improved participant’s oxygen uptake response and shortened his ventricular repolarization during steady-state aerobic exercises. By measuring the physiological and electrophysical parameters, this case report adds new evidence for the benefits of RIPC. This study also demonstrates the safety of the intervention for cardiac patients in addition to showing that the intervention is not dangerous or harmful. This provides a new approach to cardiac rehabilitation programs. Future studies with cardiac patients are needed to provide a safe, standardized exercise intervention in cardiac rehabilitation

Synthesis of carboxylate Cp*Zr(IV) species : towards the formation of novel metallocavitands

With the intent of generating metallocavitands isostructural to species [(CpZr)3(μ(3)-O)(μ(2)-OH)3(κO,O,μ(2)-O2C(R))3](+), the reaction of Cp*2ZrCl2 and Cp*ZrCl3 with phenylcarboxylic acids was carried out. Depending on the reaction conditions, five new complexes were obtained, which consisted of Cp*2ZrCl(κ(2)-OOCPh) (1), (Cp*ZrCl(κ(2)-OOCPh))2(μ-κ(2)-OOCPh)2 (2), [(Cp*Zr(κ(2)-OOCPh))2(μ-κ(2)-OOCPh)2(μ(2)-OH)2]·Et2O (3·Et2O), [[Cp*ZrCl2](μ-Cl)(μ-OH)(μ-O2CC6H5)[Cp*Zr]]2(μ-O2CC6H5)2 (4), and [Cp*ZrCl4][(Cp*Zr)3(κ2-OOC(C6H4Br)3(μ3-O)(μ2-Cl)2(μ2-OH)] [5](+)[Cp*ZrCl4](-). The structural characterization of the five complexes was carried out. Species 3·Et2O exhibits host-guest properties where the diethyl ether molecule is included in a cavity formed by two carboxylate moieties. The secondary interactions between the cavity and the diethyl ether molecule affect the structural parameters of the complex, as demonstrated be the comparison of the density functional theory models for 3 and 3·Et2O. Species 5 was shown to be isostructural to the [(CpZr)3(μ(3)-O)(μ(2)-OH)3(κO,O,μ(2)-O2C(R))3](+) metallocavitands

On the interaction of acetone with electrophilic metallocavitands having extended cavities

We report the synthesis and characterization of tantalum–boronate trimetallic clusters of general formula {[Cp*Ta]3(μ2-RB(O)2)3(μ2-OH)(μ2-O)2(μ3-OH)} (R= 4-(C6H5)(C6H4) (Ta3-4Ph), 4-(C6H5O)(C6H4) (Ta3-4OPh), 4-(C7H7O)(C6H4) (Ta3-4OBn), 4-(C8H5)(C6H4) (Ta3-4PhEt), and 4-(C12H7)(C6H4) (Ta3-4Napht)). All complexes have been characterized by NMR spectroscopy and X-ray diffraction. The trimetallic species feature a large Lewis acid type cavity allowing for substrate binding in both the solid and the liquid state using a unique electrostatic interaction and a hydrogen bond. ΔH° and ΔS° values for association of acetone with the complexes vary between −2.0 and −4.1 kcal·mol–1 and −3 and 2 cal·mol–1·K–1, respectively, showing weaker binding than smaller cavitands of the same type. The barrier for acetone exchange at equilibrium is similar for all complexes, and ΔH‡ values vary between 8.2 and 11.4 kcal·mol–1

Design et fabrication d'un senseur de pression sans fil implantable

Concepts de base, télémétrie et senseurs de pression -- Modélisation du comportement du senseur -- Fabrication du senseur

Helical Conjugated Ladder Polymers: Tuning the Conformation and Properties through Edge Design

Two helical conjugated ladder polymers (CLPs) have been synthesized using the photochemical cyclo-dehydrochlorination (CDHC) reaction on polychlorinated polymer derivatives. UV–vis and photoluminescence spectroscopy revealed that the outer chlorinated rings (phenyl or thiophene) used for the ladderization step have a significant impact on the conformation and electronic properties of the resulting polymers. The thiophene-embedded CLP exhibits strong intermolecular interactions and excimer-like emission due to a loose coil conformation while the all-phenyl CLP exhibits a tightly packed coil conformation. The helical CLPs also show good affinity toward HiPco carbon nanotubes (CNTs) as stable dispersions were prepared