Spin transport properties of spinel vanadate-based heterostructures

Spin-orbit coupling and breaking of inversion symmetry are necessary ingredients to enable a pure spin current-based manipulation of the magnetization via the spin-orbit torque effect. Currently, magnetic insulator oxides with non-dissipative characteristics are being explored. When combined with non-magnetic heavy metals, known for their large spin-orbit coupling, they offer promising potential for energy-efficient spin-orbitronics applications. The intrinsic electronic correlations characterizing those strongly correlated oxides hold the promises to add extra control-knobs to the desired efficient spin-wave propagation and abrupt magnetization switching phenomena. Spinel vanadate FeV2O4 (FVO) exhibits several structural phase transitions which are accompanied by an intricate interplay of magnetic, charge and orbital orderings. When grown as a thin film onto SrTiO3, the compressive strain state induces a perpendicular magnetic anisotropy, making FVO-based heterostructures desirable for spin-orbitronics applications. In this study, we have optimised the deposition of stoichiometric and epitaxial Pt/FVO heterostructures by Pulsed Laser Deposition and examined their spin-related phenomena. From angle-dependent magnetotransport measurements, we observed both Anisotropic Magnetoresistance (AMR) and Spin Hall Magnetoresistance (SMR) effects. Our findings show the SMR component as the primary contributor to the overall magnetoresistance, whose high value of 0.12% is only comparable to properly optimized oxide-based systems

Elaboration de cellules photovoltaïques hybrides solides à base d'oxyde de zinc nanostructuré

This thesis deals with solid state dye sensitized solar cells in which dye sensitized ZnO nanorods are associated with spiro-OMeTAD (solid hole conductor). Nanorods are grown on the top of a dense ZnO seed layer. The growth of a dense, homogeneous and well oriented layer is achieved after optimization of the deposition procedure. ZnO nanorods are obtained after submitting the dense ZnO layer to an hydrothermal treatment. The nanorods morphology evolution with reactants concentration, reaction temperature and time,… was determined. The solar cells performances depend also on the nanorods length, the type of dye, the cell ageing time in air, the atmosphere and the cell temperature…The best performance published nowadays (0.25%) for our type of photovoltaic devices is really inferior to the 1% efficiency we obtained.Cette thèse est consacrée à l’élaboration de cellules photovoltaïques hybrides solides sensibilisées à colorant, composées d’une couche dense de germes de ZnO recouverte de nanobâtonnets de ZnO sensibilisés par un colorant et infiltrés par du spiro-OMeTAD. La couche dense de germes de ZnO a été optimisée, afin qu’elle soit compacte, homogène et bien orientée. Les nanobâtonnets sont synthétisés par voie hydrothermale. L’influence de différents paramètres de synthèse sur la morphologie des nanobâtonnets a été testée. Deux méthodes permettant de modifier l’écart entre les nanobâtonnets ont également été mises au point. Les performances des cellules photovoltaïques varient en fonction de la longueur des nanobâtonnets, du colorant utilisé, de la durée de vieillissement des cellules à l’air, l’atmosphère, la température… Enfin, nous avons réussi à obtenir un rendement dépassant 1%, ce qui est supérieur à la meilleure performance publiée actuellement (0,25%) pour le même type de dispositif

Cu(OH)2 and CuO Nanorod Synthesis on Piezoresistive Cantilevers for the Selective Detection of Nitrogen Dioxide

Self-controlled active oscillating microcantilevers with a piezoresistive readout are very promising sensitive sensors, despite their small surface. In order to increase this surface and consequently their sensitivity, we nanostructured them with copper hydroxide (Cu(OH)2) or with copper oxide (CuO) nanorods. The Cu(OH)2 rods were grown, on a homogeneous copper layer previously evaporated on the top of the cantilever. The CuO nanorods were further obtained by the annealing of the copper hydroxide nanostructures. Then, these copper based nanorods were used to detect several molecules vapors. The results showed no chemical affinity (no formation of a chemical bond) between the CuO cantilevers and the tested molecules. The cantilever with Cu(OH)2 nanorods is selective to nitrogen dioxide (NO2) in presence of humidity. Indeed, among all the tested analytes, copper hydroxide has only an affinity with NO2. Despite the absence of affinity, the cantilevers could even so condensate explosives (1,3,5-trinitro-1,3,5-triazinane (RDX) and pentaerythritol tetranitrate (PETN) on their surface when the cantilever temperature was lower than the explosives source, allowing their detection. We proved that in condensation conditions, the cantilever surface material has no importance and that the nanostructuration is useless because a raw silicon cantilever detects as well as the nanostructured ones

Development of hybrid solid solar cells based on nanostructured zinc oxide

Cette thèse est consacrée à l’élaboration de cellules photovoltaïques hybrides solides sensibilisées à colorant, composées d’une couche dense de germes de ZnO recouverte de nanobâtonnets de ZnO sensibilisés par un colorant et infiltrés par du spiro-OMeTAD. La couche dense de germes de ZnO a été optimisée, afin qu’elle soit compacte, homogène et bien orientée. Les nanobâtonnets sont synthétisés par voie hydrothermale. L’influence de différents paramètres de synthèse sur la morphologie des nanobâtonnets a été testée. Deux méthodes permettant de modifier l’écart entre les nanobâtonnets ont également été mises au point. Les performances des cellules photovoltaïques varient en fonction de la longueur des nanobâtonnets, du colorant utilisé, de la durée de vieillissement des cellules à l’air, l’atmosphère, la température… Enfin, nous avons réussi à obtenir un rendement dépassant 1%, ce qui est supérieur à la meilleure performance publiée actuellement (0,25%) pour le même type de dispositif.This thesis deals with solid state dye sensitized solar cells in which dye sensitized ZnO nanorods are associated with spiro-OMeTAD (solid hole conductor). Nanorods are grown on the top of a dense ZnO seed layer. The growth of a dense, homogeneous and well oriented layer is achieved after optimization of the deposition procedure. ZnO nanorods are obtained after submitting the dense ZnO layer to an hydrothermal treatment. The nanorods morphology evolution with reactants concentration, reaction temperature and time,… was determined. The solar cells performances depend also on the nanorods length, the type of dye, the cell ageing time in air, the atmosphere and the cell temperature…The best performance published nowadays (0.25%) for our type of photovoltaic devices is really inferior to the 1% efficiency we obtained

Le manchonnage par un tube de collagène des sutures nerveuses directes et incidence des douleurs névromateuses (étude prospective de 120 cas)

Le but de cette étude est d étudier l intérêt d ajouter un tube de collagène autour des sutures nerveuses directes afin de diminuer les douleurs neuropathiques postopératoires et l incidence d apparition des névromes. Nous avons suivi prospectivement les patients ayant un nerf sectionné opérés en urgence entre janvier 2010 et mars 2011. Les sutures ont été manchonnées par un tube de collagène résorbable fixé à l épinerve. Les patients ont été examinés à 1 et 3 mois en recherchant une zone gâchette à la percussion sur la cicatrice. 120 nerfs chez 104 patients ont été suturés, tous au membre supérieur. Aucune réaction allergique ou intolérance n a été constatée. Aucune zone gâchette ne s est déclarée à la consultation du 3e mois. Notre étude montre que le manchonnage systématique des sutures directes par un tube de collagène a diminué l incidence des douleurs neuropathiques postopératoires.PARIS6-Bibl.Pitié-Salpêtrie (751132101) / SudocSudocFranceF

Elaboration de cellules photovoltaïques hybrides solides à base d'oxyde de zinc nanostructuré

Cette thèse est consacrée à l élaboration de cellules photovoltaïques hybrides solides sensibilisées à colorant, composées d une couche dense de germes de ZnO recouverte de nanobâtonnets de ZnO sensibilisés par un colorant et infiltrés par du spiro-OMeTAD. La couche dense de germes de ZnO a été optimisée, afin qu elle soit compacte, homogène et bien orientée. Les nanobâtonnets sont synthétisés par voie hydrothermale. L influence de différents paramètres de synthèse sur la morphologie des nanobâtonnets a été testée. Deux méthodes permettant de modifier l écart entre les nanobâtonnets ont également été mises au point. Les performances des cellules photovoltaïques varient en fonction de la longueur des nanobâtonnets, du colorant utilisé, de la durée de vieillissement des cellules à l air, l atmosphère, la température Enfin, nous avons réussi à obtenir un rendement dépassant 1%, ce qui est supérieur à la meilleure performance publiée actuellement (0,25%) pour le même type de dispositif.This thesis deals with solid state dye sensitized solar cells in which dye sensitized ZnO nanorods are associated with spiro-OMeTAD (solid hole conductor). Nanorods are grown on the top of a dense ZnO seed layer. The growth of a dense, homogeneous and well oriented layer is achieved after optimization of the deposition procedure. ZnO nanorods are obtained after submitting the dense ZnO layer to an hydrothermal treatment. The nanorods morphology evolution with reactants concentration, reaction temperature and time, was determined. The solar cells performances depend also on the nanorods length, the type of dye, the cell ageing time in air, the atmosphere and the cell temperature The best performance published nowadays (0.25%) for our type of photovoltaic devices is really inferior to the 1% efficiency we obtained.STRASBOURG-Bib.electronique 063 (674829902) / SudocSudocFranceF

Additional figures from Synthesis of zinc oxide nanorods or nanotubes on one side of a microcantilever

Additional figure

Cu(OH)2 and CuO Nanorod Synthesis on Piezoresistive Cantilevers for the Selective Detection of Nitrogen Dioxide

Self-controlled active oscillating microcantilevers with a piezoresistive readout are very promising sensitive sensors, despite their small surface. In order to increase this surface and consequently their sensitivity, we nanostructured them with copper hydroxide (Cu(OH)2) or with copper oxide (CuO) nanorods. The Cu(OH)2 rods were grown, on a homogeneous copper layer previously evaporated on the top of the cantilever. The CuO nanorods were further obtained by the annealing of the copper hydroxide nanostructures. Then, these copper based nanorods were used to detect several molecules vapors. The results showed no chemical affinity (no formation of a chemical bond) between the CuO cantilevers and the tested molecules. The cantilever with Cu(OH)2 nanorods is selective to nitrogen dioxide (NO2) in presence of humidity. Indeed, among all the tested analytes, copper hydroxide has only an affinity with NO2. Despite the absence of affinity, the cantilevers could even so condensate explosives (1,3,5-trinitro-1,3,5-triazinane (RDX) and pentaerythritol tetranitrate (PETN) on their surface when the cantilever temperature was lower than the explosives source, allowing their detection. We proved that in condensation conditions, the cantilever surface material has no importance and that the nanostructuration is useless because a raw silicon cantilever detects as well as the nanostructured ones

Double side nanostructuring of microcantilever sensors with TiO2-NTs as a route to enhance their sensitivity

International audienceWe reported a new strategy to enhance the sensing performances of a commercial microcantilever with optical readout in dynamic mode for the vapor detection of organophosphorus compounds (OPs). In order to increase significantly the surface area accessible to the molecules in the vapor phase, we nanostructured both sides of the microcantilever with ordered, open and vertically oriented amorphous titanium dioxide nanotubes (TiO2-NTs) in one step by an anodization method. However, due to the aggressive conditions of anodization synthesis it remains a real challenge to nanostructure both sides of the microcantilever. Consequently, we developed and optimized a protocol of synthesis to overcome these harsh conditions which can lead to the total destruction of the silicon microcantilever. Moreover, this protocol was also elaborated in order to maintain a good reflection of the laser beam on one side of the microcantilever towards the position sensitive photodiode and limit the light diffusion by the NTs film. The results related to the detection of dimethyl methylphosphonate (DMMP) showed that TiO2 and the nanostructuring on both sides of the microcantilever with NTs indeed improved the response of the sensor to vapors compared to a microcantilever nanostructured on only one side. The dimensions and morphology of NTs guaranteed the access of molecules to the surface of NTs. This approach showed promising prospects to enhance the sensing performances of microcantilevers

Optimization of a New ZnO Nanorods Hydrothermal Synthesis Method for Solid State Dye Sensitized Solar Cells Applications

We report on the growth control of zinc oxide nanorods to point out the effect of the ZnO nanorods quality on the power conversion efficiency (PCE) of transparent conductive oxide (TCO)/ZnO nanorods/dye/spiro-OMe-TAD/metal electrode photovoltaic devices. A promising PCE of 0.61% was measured for the best nanorods growth conditions. A careful control of all the growth parameters during the seeds layer deposition and the hydrothermal synthesis was necessary to reach such a high PCE for this kind of device. A regular nanorod layer with a flat upper surface was obtained for ethylenediamine to zinc acetate dihydrate molar ratio equal to 1.74 and a pH of 8.2. The growth was performed at 65 degrees C for 2 h to avoid zinc oxide brushes deposition on the surface, arising from zinc hydroxyacetate decomposition during the hydrothermal treatment. The effect of ZnO nanorods length (ranging from 1 to 3 mu m) on solar cell efficiency was tested. Although the UV-vis absorption increases when the nanorods length increases, the best photovoltaic parameters were measured for the shortest nanorods length studied (1 mu m)