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Laazizi, Abdellah. "Contribution à l'étude du procédé de traitement des matériaux par faisceau laser pulsé : confrontation simulation-expérience". Nantes, 2006. http://www.theses.fr/2006NANT2124.
Pełny tekst źródłaThe simulation of the material treatments process by laser beam is a fundamental stage to optimize the operative parameters. The analytic or semi-analytic approaches described in the literature are limited by restrictive assumptions. Numerical simulations allow to take into account phenomena really encountered, particularly, when fusion of the treated material appears and convection movements in the melted bath take place. In this work, we have developed a numerical simulation of heat transfer taking into account the displacement of the laser beam, the convection movements, phase transformations and the dependence on temperature of the thermal and physical properties. The transient heat equation is solved by using a finite differences method with an explicit or implicit scheme following the intensity of the convection movements. The velocity-pressure coupling problem, present in the conservation and continuity equations, is solved by an iterative algorithm SIMPLE. Two different materials have been studied to validate the simulated results : a stainless steel X30Cr13 and an almost pure Iron (99. 8%). Regarding the experimental procedure, two pulsed Nd-YAG laser have been used, as part of a collaboration with the Laboratoire Procédés – Matériaux – Instrumentation from the ENSAM of Angers and the Laser et Traitement des matériaux laboratory from the IUT of Creusot. When low power irradiations are used, simulation and experimental results about the width and depth of the melted zone are in good agreement. For high power irradiations, a Keyhole effect appears and so simulation and experimental results do not fit
Li, Hui. "Rôle d'une ablation laser in situ sur les propriétés mécaniques d'un revêtement élaboré par projection thermique". Besançon, 2006. http://www.theses.fr/2006BESA2011.
Pełny tekst źródłaThe PROTAL® process combines a nanosecond pulsed laser treatment with thermal spraying. However, the physico-chemical effects induced by the laser irradiation have not been well clarified. This study aims at investigating the mechanisms of laser induced surface modifications and its influence on the deposit adhesion. The surface morphological modifications induced by laser were estimated by varying the laser energy density and the number of laser shots. It was shown that the laser induced modifications related to the thermalisation phenomena. It is thus noted that the laser-matter interaction depends strongly on the surface conditions and the properties of treated materials. For all materials studied in this work, the formation of craters caused by a preferential ablation appears. This phenomenon becomes more intensive by increasing the energy density or the number of shots. For titanium alloy substrates, another notable aspect was the surface smoothing effect, which is probably linked to the formation of a thin layer on the outmost surface. The laser irradiation effects on the splat flattening and on the splash phenomenon were also studied. The laser treatment which permits to generate favourable surface conditions for splat formation was highlighted. It was also shown that the splashing of the particles related to the evaporation of various surface absorbates/condensates of surface. Both the particle's energy and the substrate nature also play a role during the splat flattening process. The significant effect of this laser treatment on deposit adhesion seems related to the improvement of physical bonding because it was verified that laser treatment permits to remove various contaminants as well as oxide layers and therefore improve the deposit adhesion. However, for titanium alloy substrate, the superficial film induced by the laser seems to limit metallurgical bonding at the interface, while for aluminium alloy substrate, craters with the form of deep cavities tends to deteriorate the interfacial adhesion. Therefore, it was proposed that the choice of laser parameters is, on the one hand to clean the surface contaminants efficiently and on the other hand to avoid further damage to the substrate
Stock, François. "Traitements laser UV de couches de carbone amorphe adamantin (DLC) obtenues par ablation laser pulsée (PLD) : application à la synthèse d'électrodes transparentes". Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAD035.
Pełny tekst źródłaOne of the biggest challenge that optoelectronic and photovoltaic devices will have to face is the necessity to provide a reliable alternative to transparent conducting oxide (TCO) and especially to Indium Thin Oxide (ITO) widely used in display technologies. This thesis presents an alternative solution based on laser processes and carbon materials only. In a first step, Diamond-Like Carbon (DLC) is grown with a pulsed laser deposition (PLD) process. DLC is an amorphous form of carbon sharing many properties with diamond like very high transparency in the visible range and being a perfect electrical insulator. Therefore, in a second step, DLC thin films are annealed with UV laser. These surface treatments lead to the modification of the first DLC atomic layers. With this step, dominating diamond bindings (sp3) responsible of insulating properties of DLC are broken and atoms will be reorganized in graphitic bindings (sp2) leading to surface conductivity appearance. Within only surface modifications (over a few atomic layers), the interesting property of transparency is conserved with an additional attractive surface conductivity. Obtained performances clearly approach and reach ITO values. This only laser-based process offers very interesting perspectives with keeping an important compatibility with standard microelectronics technical steps
MASSON, ISABELLE. "Le traitement des calculs de l'uretere par ureteroscopie couplee au laser pulse : a propos de 30 cas". Nice, 1991. http://www.theses.fr/1991NICE6524.
Pełny tekst źródłaTotems, Julien. "Emission laser impulsionnelle et traitements temps-fréquence en vibrométrie par lidar à détection cohérente". Phd thesis, Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00610531.
Pełny tekst źródłaDanlos, Yoann. "Etude de l'association laser-projection thermique pour l'optimisation de revêtements". Phd thesis, Université de Technologie de Belfort-Montbeliard, 2009. http://tel.archives-ouvertes.fr/tel-00603636.
Pełny tekst źródłaFOURNIER, JEAN. "Generation d'ondes de choc par laser pulse de forte energie : applications mecaniques et metallurgiques". Palaiseau, École polytechnique, 1989. http://www.theses.fr/1989EPXX0007.
Pełny tekst źródłaDupont, Préscillia. "Texturisation laser sélective des aciers électriques orientés et non orientés pour l'optimisation de leur perméabilité et des pertes dans les machines électriques tournantes". Electronic Thesis or Diss., Amiens, 2022. http://www.theses.fr/2022AMIE0065.
Pełny tekst źródłaSoft ferromagnetic materials, which are often used in the form of laminated sheets, compose rotating electrical machines' stators and rotors. The efficiency of those machines is reduced by losses called "iron losses", induced by magnetization mechanisms and eddy currents. Those magnetization reversal mechanisms can only be explained with the magnetic structure coupled to the material geometry, anisotropy and surface texture, which are also deterministic factors for the final electromagnetic performances. Then, present work aims at proposing tailor-made soft ferromagnetic materials by means of selective laser texturizing for electromagnetic devices such as rotating electrical machines. To apply such a process at an industrial level for grain-oriented and non-grain-oriented materials in electrical machines, it is necessary to better control the associated technology and specify the process in order to optimize electromagnetic properties. Indeed, the deterministic impact of this technic on a material's magnetic structure and its performances (magnetic permeability and iron losses) remains partially modelled and understood. The integration of such solution at the industrial scale must be analyzed and optimized regarding technical and economical constraints. In this work, the study of the impact of laser surface texturizing on magnetic structure (regarding surface and volume) of a material with the aim to control it is performed. Future industrialization requires to adapt the pulsed laser processes at a higher speed which has been theoretically studied, initiated and experimentally verified. To finish, present work performed in parallel with the H2020 European project ESSIAL will allow to propose different surface treatments adapted to rotating machines to adjust some quantifiable electromagnetic properties with the help of both experimental and theoretical tools
Pezé, Pascale. "Étude et caractérisation par fluorescence induite par laser d'un jet pulsé d'oxygène atomique". Toulouse, ENSAE, 1993. http://www.theses.fr/1993ESAE0021.
Pełny tekst źródłaEsmiller, Bruno. "Caractérisation par spectroscopie d'émission de plasmas induits par laser verre-néodyme déclenché sur matériaux solides". Aix-Marseille 2, 1993. http://www.theses.fr/1993AIX22080.
Pełny tekst źródłaAutier-Laurent, Sandrine. "Films minces d'oxydes préparés par ablation laser pulsé : répliques du matériau massif ?" Caen, 2005. http://www.theses.fr/2005CAEN2041.
Pełny tekst źródłaFariaut, François. "Traitement de surface par laser excimère". Orléans, 2002. http://www.theses.fr/2002ORLE2049.
Pełny tekst źródłaBenzerga, Ratiba. "Optimisation de la croissance de couches minces de composés par ablation laser". Orléans, 2005. http://www.theses.fr/2005ORLE2065.
Pełny tekst źródłaAllain, Mickael. "Croissance et études de films minces et d'hétérostructures d'oxydes pérovskites réalisés par dépôt laser pulsé". Thesis, Versailles-St Quentin en Yvelines, 2014. http://www.theses.fr/2014VERS0053/document.
Pełny tekst źródłaThis thesis work has been led to study the growth by Pulsed Laser Deposition (PLD) and theproperties of different perovskite oxide systems including heterostructures of LaAlO3/SrTiO3,SrVO3/SrTiO3 and LaAlO3/SrVO3. This work is motivated by the need to measure and analyze theinterface properties in these systems which are composed with transition metal elements titaniumand vanadium but with different electronic configuration, 3d0 for Ti and 3d1 for V that can modify theproperties.In a first part, growth and characterizations – structural, transport and magnetism – is presented.Major results are obtained and demonstrate the effect of growth conditions – oxygen pressure andlaser fluence – on LaAlO3 thin films stoichiometry and interface electronic properties finally provingthe existence of an electronic phase transition.In the second part, growth of thin and ultrathin SrVO3 films is detailed and an experimentalobservation of the Metal-Insulator Transition (MIT) is brought out. The origin of this MIT isdemonstrated by structural and Transport properties investigation. Furthermore, physicalmechanisms of conduction in this system are revealed through modelisation work.Finally, the last part is devoted to the work done on LaAlO3/SrVO3 heterostructures grown on SrTiO3and LaAlO3 substrates. Transport characterizations and chemical analysis realized in order to studythe interface properties and to compare with LaAlO3/SrTiO3. Different conduction mechanisms havebeen brought out which are correlated by chemical analysis – for samples grown on SrTiO3 – anddemonstrate the effect of LaAlO3 thin films in this hétérostructure
Guyard, Sabrina. "Epitaxie par ablation laser pulsé du titanate de strontium : application aux dispositifs agiles hyperfréquences". Paris 6, 2007. http://www.theses.fr/2007PA066029.
Pełny tekst źródłaThe association of a ferroelectric SrTiO3 with a superconductor YBa2Cu3O7 allows to produce filters which commutate quickly in frequency under the effect of an electric field. These filters are microwave devices known as “tunable” in frequency. A broad panel of experimental techniques was used to study in-situ surfaces and growths and to analyze ex-situ physicochemical properties of SrTiO3. These analyses revealed the origins of the quadratic deformation of the films and showed a correlation between dielectric losses and the microstructure analyzed with TEM and Raman. The enrichment of the target with strontium during growths causes a deterioration of the dielectric properties of SrTiO3. Changing the target every 15 hours makes it possible to preserve the performances and to produce demonstrator microwave tunable filters with excellent characteristics: at 6GHz and 77K, 10% to 20% of agreement, Q0 of 1000 and tanof 5×10-3 at 10V/m
Jaren, Sophie. "Étude de TbFe2 épitaxié par dépot laser pulsé : des couches minces aux nanostructures magnétiques". Université Joseph Fourier (Grenoble ; 1971-2015), 1998. http://www.theses.fr/1998GRE10064.
Pełny tekst źródłaFleury, Nicolas Pierre. "Le traitement des sténoses urétrales par laser /". Genève : Ed. Médecine et hygiène, 2003. http://www.unige.ch/cyberdocuments/theses2002/FleuryN/these.pdf.
Pełny tekst źródłaMaury, Cécile. "Spectroscopies analytiques innovantes pour l'amélioration de la sûreté des réacteurs nucléaire à neutrons rapides refroidis au sodium". Paris 6, 2012. http://www.theses.fr/2012PA066428.
Pełny tekst źródłaBonilla, Francisco Javier. "Nanofils ferromagnétiques auto-assemblés de Co, Ni et d’alliages CoNi : croissance, structure et propriétés magnétiques". Paris 6, 2013. http://www.theses.fr/2013PA066244.
Pełny tekst źródłaThis thesis reports on the study of self-assembled ferromagnetic nanowires of Co, Ni and CoNi alloys embedded in a CeO2/SrTiO3(001) matrix. These systems are grown by pulsed laser deposition. The nanowires have diameters in a 1. 5 -7 nm range, depending on the growth conditions, and densities above 1 Tb/inch2. For each type of nanowires (NWs) assembly (Co, Ni, CoNi alloys), the composition, morphology, crystalline structure and magnetic properties were studied using a combination of techniques (X-ray absorption spectroscopy, transmission electron microscopy, X-ray diffraction, magnetometry). Co-NWs are textured and anisotropic, with an easy axis along the wire axis. The correlation between the magnetic response and the structure is evidenced and corroborated by means of a model for the mechanism of magnetization reversal. Ni-NWs are monocrystalline and epitaxied with the surrounding matrix. Contrary to Co-NWs, the Ni-NWs are not anisotropic. Structural studies reveal an axial deformation of the Ni lattice. This introduces a magnetoelastic anisotropy term competing with the wires shape anisotropy. The compensation of the different anisotropies in the Ni-NWs is further supported by of micromagnetic simulations. Based on these results, some alternatives to tune the magnetic anisotropy in Ni-NWs are presented. CoxNi1-x alloy NWs, obtained from a combinatorial growth method, are monocrystalline, epitaxied and anisotropic. It is shown that the total magnetic anisotropy of the system can be tuned by controlling the Co content in alloy NWs. Finally, perspectives issued from this work are sketched
Mistrik, Jan. "Etudes des propriétés physiques par spectroscopie magnéto-optique de couches minces d'oxydes magnétiques préparé par dépôt laser pulsé". Versailles-St Quentin en Yvelines, 2002. http://www.theses.fr/2002VERS0024.
Pełny tekst źródłaBoch, Elisabeth. "Etude de la photodécomposition du silane et du disilane par un rayonnement laser pulsé ArF". Université Louis Pasteur (Strasbourg) (1971-2008), 1990. http://www.theses.fr/1990STR13163.
Pełny tekst źródłaMuniz, Pedro Schio de Noronha. "Propriétés magnétiques de nanofils de cobalt auto-assemblés élaborés par ablation laser pulsée". Paris 6, 2012. http://www.theses.fr/2012PA066118.
Pełny tekst źródłaThe subject of this thesis is the study of cobalt nanowires self-assembled in a CeO2 matrix. The spontaneous self-assembly of nanowires occurs in strongly Co-doped CeO2 thin films grown by pulsed laser deposition. The metallic character of Co was attested by analysis of X-Ray absorption spectra taken at the Co K-edge. The formation of nanowires could be evidenced by transmission electron microscopy experiments (high resolution and energy filtered modes). Combining these results led to the conclusion of Co nanowires formation in the CeO2 matrix. The nanowires are oriented parallel to the growth direction; have length up to the thickness of film and have a narrow diameter size distribution centered in the 3 - 7 nm range. Due to the reduced values of diameter, these nanowires assemblies are model systems for studies in nanomagnetism. The magnetic properties of two nanowires assemblies (with diameters distribution centered on 3 and 5 nm) were investigated in details. The inner structure could be determined by means of transmission electron microscopy and the magnetization reversal was probed through static and dynamic magnetization measurements. Investigation of the magnetic anisotropy was carried out by analysis of resonance ferromagnetic spectra. The localization of the magnetization reversal was related to the inner structure of nanowires, more precisely to the orientation of hcp Co grains. In these grains, shape and magnetocrystalline anisotropies compete in strength and direction, leading to a thermally dependent effective anisotropy. The results presented indicate that it is possible to correlate the magnetic behavior with the real structure of wires in these systems
Richard, Alain. "Traitement de trempe superficielle par laser du zircaloy". Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37600824k.
Pełny tekst źródłaGatti, Sylvain. "Inscription laser UV pulsé sur nouveau matériau hybride pour codeurs optiques intégrés". Phd thesis, Montpellier 2, 2007. http://www.theses.fr/2007MON20238.
Pełny tekst źródłaLa technologie sol-gel a déjà démontré son potentiel. Un nouveau matériau sol-gel hybride à polymérisation cationique de type Epoxy a été développé dans le but de la simplification de la synthèse et de l'amélioration des performances en particulier l'adhérence.
Ce travail a pour objectif le développement d'un banc d'écriture laser UV dans une couche Epoxy et l'établissement du protocole de fabrication associé. Ce procédé de polymérisation locale est une alternative prometteuse aux techniques lithographiques par masque.
Ce nouveau banc utilise un laser pulsé travaillant à faible longueur d'onde pour une meilleure résolution et une meilleure polymérisation.
Ce travail a montré la faisabilité de circuits complexes de type multiplexeurs WDM avec un procédé d'inscription à faible coût. Nous avons réalisé les premiers prototypes de circuits dédiés à la sélection multiple de longueurs d'onde pour le (dé)codage du CDMA optique spectral.
Gatti, Sylvain. "Inscription laser UV pulsé sur nouveau matériau hybride pour codeurs optiques intégrés". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2007. http://tel.archives-ouvertes.fr/tel-00258256.
Pełny tekst źródłaLa technologie sol-gel a déjà démontré son potentiel. Un nouveau matériau sol-gel hybride à polymérisation cationique de type Epoxy a été développé dans le but de la simplification de la synthèse et de l'amélioration des performances en particulier l'adhérence.
Ce travail a pour objectif le développement d'un banc d'écriture laser UV dans une couche Epoxy et l'établissement du protocole de fabrication associé. Ce procédé de polymérisation locale est une alternative prometteuse aux techniques lithographiques par masque.
Ce nouveau banc utilise un laser pulsé travaillant à faible longueur d'onde pour une meilleure résolution et une meilleure polymérisation.
Ce travail a montré la faisabilité de circuits complexes de type multiplexeurs WDM avec un procédé d'inscription à faible coût. Nous avons réalisé les premiers prototypes de circuits dédiés à la sélection multiple de longueurs d'onde pour le (dé)codage du CDMA optique spectral.
Bercot, Patrice. "Etude des revêtements d'or obtenus par courants pulsés : corrélation entre plage faradique et certaines caractéristiques de tels revêtements". Université de Franche-Comté. UFR des sciences et techniques, 1988. http://www.theses.fr/1988BESA2005.
Pełny tekst źródłaNelea, Valentin Dan. "Croissance et caractérisation des couches minces d'hydroxyapatite obtenues par la méthode de dépôt laser pulsé (PLD)". Université Louis Pasteur (Strasbourg) (1971-2008), 2002. http://www.theses.fr/2002STR13228.
Pełny tekst źródłaHernandez-Perez, Maria de los Angeles. "Propriétés structurales et optiques de films minces élaborés par dépôt par ablation laser de molécules organiques de type acides aminés, calix-arènes et protéines". Lyon 1, 2005. http://www.theses.fr/2005LYO10190.
Pełny tekst źródłaDéziel, Jean-Luc. "Ablation laser et croissance de réseaux de surface". Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26377.
Pełny tekst źródłaLa formation des réseaux de surface, ou laser-induced periodic surface structures (LIPSSs), à l’aide d’une source laser pulsée est étudiée avec la théorie de Sipe-Drude, d’abord analytiquement, puis avec la méthode numérique finite-difference time-domain (FDTD). Les LIPSSs sont des structures nanométriques sinusoïdales pouvant être catégorisées selon leur orientation par rapport à la direction de polarisation du laser incident et en fonction de leur période Λ par rapport à la longueur d’onde du laser λ. Avec la méthode FDTD, nous trouvons, dans une région de l’espace paramétrique jamais explorée, qu’une impulsion laser polarisée linéairement peut interagir avec une surface rugueuse de façon à faire croître des structures bidimensionnelles ayant une période de Λ ∼ λ dans les orientations parallèle et orthogonale à la direction de polarisation. Par contre, ce modèle ne peut expliquer la forte organisation et régularité des structures dans le domaine spatial, tel qu’observé dans les expériences. Permettre l’auto-organisation des structures avec un mécanisme de rétroaction inter-impulsion est une solution possible afin de simuler la croissance de LIPSSs fortement organisés d’une impulsion laser à la suivante. Récemment proposée, cette méthode utilise un processus d’ablation non physique afin de tenir compte qualitativement de l’éjection de matériau entre deux impulsions laser. Ce nouveau modèle peut reproduire une grande variété de LIPSSs avec une forte régularité spatiale, mais échoue toujours à simuler la croissance de l’amplitude de certains types de structures. Nous suggérons que ces structures restantes peuvent croître en considérant un mécanisme inverse, l’expansion. En combinant ablation et expansion, nous avons simulé avec succès un plus grand nombre de types de LIPSSs.
The formation of laser-induced periodic surface structures (LIPSSs) using pulsed laser source is studied on the basis of the Sipe-Drude theory solved, first analytically, then with a finitedifference time-domain (FDTD) scheme. LIPSSs consist of wavy nanometric structures and can be categorized depending on their orientation with respect to the incident laser polarization and their periodicity Λ with respect to the incident laser wavelength λ. With our FDTD solver, we find, in as yet unexplored regions of parameter space, that a linearly polarized laser pulse can interact with a rough surface such that bidimensional structures could grow with both parallel and perpendicular periodicity of Λ ∼ λ. However, this theory cannot predict the strong organization and regularity in the space domain, as observed in the experiments. Allowing self-organization in the model with an interpulse feedback mechanism is a possible solution to simulate the growth of strongly organized LIPSSs from one laser pulse to the next. This recently proposed method uses a non-physical ablation process to qualitatively account for material removal between two laser pulses. This new model can reproduce a large variety of LIPSSs with a strong spatial regularity, but still fails to simulate amplitude growth of some of the structures. We suggest that those remaining structures can grow by considering an inverse mechanism, an expansion process. By combining ablation and expansion mechanisms, we have successfully simulated the growth of a large class of LIPSSs.
Sikora, Aurélien. "Incorporation de bore dans des films minces de « diamond-like carbon » : élaboration par ablation laser pulsé et caractérisations". Saint-Etienne, 2009. http://www.theses.fr/2009STET4018.
Pełny tekst źródłaThis work deals with the study of boron doped diamond-like carbon thin films elaborated by femtosecond and nanosecond laser ablation. The first aim of this work consists in identifying the potential applications of these films for sensors (for example thermometers). The second aim consists in correlating the films structure and properties with the deposition processes. The first chapter focused on the constitutive elements of the films: boron and carbon. Moreover, it presents a “state of the art” about DLC thin films and the different elaboration techniques. The second chapter deals with the experimental methods used for the elaboration and the study of the thin films. The third chapter deals with the structural and morphological characterizations. It highlights the important difference of structure of the films deposited by ns and fs PLD. Moreover, it underlines the structural modification due to the boron. The fourth chapter presents the study of the electrical and mechanical properties, as well as the tribological behaviour of the films. The structure difference of the films results in large variations of resistivity but does not change much the friction coefficient. The last chapter underlines the structural heterogeneity of the pure DLC films and focuses on the specificities of their extreme surface. This one turns out to be less dense and more conductor than the global film
Petat, Bertrand. "Contribution à l'étude de la nitruration du fer par un plasma continu-pulsé". Nancy 1, 1990. http://www.theses.fr/1990NAN10541.
Pełny tekst źródłaPrudhomme, Michel. "Traitement des tumeurs hépatiques par thermothérapie interstitielle induite par le laser diode". Montpellier 1, 2000. http://www.theses.fr/2000MON1T020.
Pełny tekst źródłaFouchet, A. "Croissance et caractérisations de films minces de ZnO et ZnO dopé cobalt préparés par ablation laser pulsé". Phd thesis, Université de Caen, 2006. http://tel.archives-ouvertes.fr/tel-00199703.
Pełny tekst źródła- Le ferromagnétisme est intrinsèque ou extrinsèque ?
- Quel est le mécanisme relatif aux interactions magnétiques ?
Pour répondre à ces questions une méthode originale de dépôt en couche mince par ablation laser a été mise en place à partir de l'utilisation de deux cibles métalliques. Cette étude a donc été réalisée en deux étapes : l'optimisation des conditions de dépôt du ZnO puis l'utilisation des ses conditions pour incorporer le cobalt. De plus, la concentration en cobalt des films a été fixée et nous avons étudié l'influence des conditions de dépôts. Il en a résulté que le substrat jouait un rôle important dans la croissance des films et nous en avons déduit que les défauts sont nécessaires à l'apparition du ferromagnétisme. Ceci en accord avec les derniers développements théoriques. Enfin, une comparaison avec des films réalisés à partir des cibles céramiques a confirmé ses résultats.
Fouchet, Arnaud. "Croissance et caractérisations de films minces de ZnO et ZnO dopé cobalt préparés par ablation laser pulsé". Caen, 2006. http://www.theses.fr/2006CAEN2050.
Pełny tekst źródłaSpintronics is an emergent area of research that exploits the quantum propensity of electrons to spin as well as utilizing their charge state, allowing microelectronic devices to be devised with additional functionality. Indeed, a great deal of research activity has been focused on dilute magnetic semiconductors (DMS) owing to their potential application as room temperature spintronic devices. This is based on recent theoretical calculations that predict it is possible to design DMS materials possessing ferromagnetic transitions (FM-Tc) above room temperature by doping a magnetic element into a host wide bandgap semiconductor (e. G. , Co-doped ZnO). However, the origin of ferromagnetism in these DMS materials is still subject of controversy, and questions remain : - is ferromagnetism in DMS intrinsic or extrinsic ? and - what is the mechanism relative to the magnetic interactions ? To address these questions, we have developed a novel strategy for the pulsed laser deposition of Co-doped ZnO films that utilizes metallic targets as the source of cationic elements. First, the growth conditions for ZnO films were optimized, and then subsequently utilized to deposit Co-doped ZnO films. Second, because this method allows for the precise control of the Co/Zn composition the growth conditions for certain amounts of cobalt doped into ZnO also were systematically studied. As a result, we have correlated the presence of ferromagnetism to film defects, results which have supported by recent theoretical calculations. Moreover, these results were corroborated by a comparative study between Co-doped ZnO films grown by ceramic and metallic targets
Coulon, Jérôme. "Films manganites orientés présentant une transition métal-isolant : dépôt par ablation laser, intégration sur silicium". Tours, 2003. http://www.theses.fr/2003TOUR4028.
Pełny tekst źródłaIn function of substitutions, the manganites oxydes with perovskite structure present a dramatic evolution of the electric properties. This shows the possibilities of making a limitor of current and voltage. The technique chooses to grown the films and preserves the cristallinity, is the pulsed laser deposition. The La0. 8Sr0. 2MnO3 grown without preferential orientation on Si substrate. A part of this study point on the development of a buffer layer. A original method of manganite fine powder synthesis have been used and it sintering have been optimized. The conductivity properties of the bulk nickelate are equivalent of the film only when the growth conditions are under control. The films of manganite are oriented but the properties near of the crystal are finding again for the lanthane aluminate substrate, which have the biggest mismatch with the manganite. The result shows the dramatic sensibility of manganite layer to the strains due to the grown and the mismatch
Bieber, Herrade. "Couches minces de ZnCoO déposées par ablation laser pulsée : effet de dopage sur les propriétés structurales et magnétiques". Strasbourg, 2009. http://www.theses.fr/2009STRA6134.
Pełny tekst źródłaThe combination of the charge and the spin of the electron giving rise to the new field of spintronics, has led to the realization of new devices amongst others in the field of data storage. Till now, the major difficulty to realize such devices was to obtain spin injection of controlled spin direction into a semi-conductor. Indeed the spin injection from a ferromagnetic metal into a semi-conductor is restrained by the difference of resistivity in both materials. One solution consisted in making the semi-conductor ferromagnetic. Such diluted magnetic semi-conductors (DMS) are composed of a semi-conducting matrix, in which a part of the ions is replaced by magnetic ions. Co-doped zinc oxide is a promising DMS, as it is predicted a Curie temperature above room temperature for this material when doped with transition metals thus giving additional charge carriers. Nevertheless, the origin of the observed ferromagnetism in literature remains controversial. We have thus studied thin films of ZnCoO deposited by pulsed laser deposition. The study has then been focused on the influence of the polarity of charge carriers on the structural and magnetic properties of the thin films by additional doping with silver and aluminum. We have evidenced the importance of the presence of defects on the origin of the observed ferromagnetism in the thin films
Chaoui, Nouari. "Ablation laser d'oxydes : apport de la spectrométrie de masse à la compréhension des mécanismes d'élaboration de films minces". Metz, 1998. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1998/Chaoui.Nouari.SMZ9842.pdf.
Pełny tekst źródłaQuerré, Madec. "Couches minces de V2O3:Cr et réalisation de mémoires résistives de Mott". Nantes, 2016. https://archive.bu.univ-nantes.fr/pollux/show/show?id=6066e6b4-1b11-45c9-9449-65add4440ea3.
Pełny tekst źródłaVanadium sesquioxide substituted with chromium (V1-xCrx)2O3 is a narrow gap Mott insulator in which the application of electric pulses induces a resistive switching of several orders of magnitude related to an insulator to metal transition. Initially observed in single crystals, such reversible non-volatile transitions arise from an electronic avalanche breakdown phenomenon which is universal to all Mott insulators. This resistive switching is very interesting for applications in a new type of non-volatile resistive memory ReRAM, the Mott memory. However, using these materials for memory applications requires a critical step of thin films deposition. We synthesized (V1-xCrx)2O3 thin films, first by pulsed laser deposition in order to validate that the resistive switching initially observed in single crystals also appears in thin films. Then, we developed the reactive DC magnetron co-sputtering technique under Ar/O2, which requires a more important optimization process, while being easily transferable to microelectronic industry. By both techniques, we synthesized (V1-xCrx)2O3 Mott insulator thin films well controlled in terms of purity, crystallinity, chromium content and oxygen stoichiometry. We implemented then Mott memories micro devices based on a symmetrical TiN/(V1-xCrx)2O3 /TiN MIM architecture. The memory performances of such devices, namely amplitude, voltage and pulse duration, endurance, retention, appear as very promising compared to those of other emerging non-volatile memories
Rousseau, Anthony. "Couches minces d'oxydes ferroélectriques pour les dispositifs agiles en hyperfréquences : croissance par ablation laser et caractérisations". Rennes 1, 2005. http://www.theses.fr/2005REN1S123.
Pełny tekst źródłaAl, Khawwam Anas. "Dépôt de nitrure de carbone par ablation laser IR sous atmosphère de post-décharge d'azote". Lille 1, 2002. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2002/50376-2002-179.pdf.
Pełny tekst źródłaSuwardi. "Modélisation thermique du traitement de surface par faisceau laser : application au traitement thermique superficiel". Vandoeuvre-les-Nancy, INPL, 1991. http://www.theses.fr/1991INPL038N.
Pełny tekst źródłaAISENFARB, JEAN-CHARLES. "Traitement des troubles du rythme ventriculaire d'origine ischemique par laser". Lille 2, 1989. http://www.theses.fr/1989LIL2M249.
Pełny tekst źródłaBrizé, Virginie. "Elaboration de céramiques CaCu3Ti4O12 à haute constante diélectrique et réalisation de condensateurs "tout oxyde" par ablation laser pulsé". Tours, 2006. http://www.theses.fr/2006TOUR4026.
Pełny tekst źródłaThe oxide CaCu3Ti4O12 (CCTO) shows a very high permittivity (~ 105) in a large range of temperature (100-60K) and frequencies (10Hz-1MHz). A part of this study is an atttempt to deposit "all oxide" capacitors based on CCTO using the laser on CCTO using the laser ablation technique. At first, epitaxial films of CCTO were deposited on single crystal LaA1O3(100) (LAO) after optimisation of the target sintering. Capacitors LSNO/CCTO/LSNO/LAO with LaSrNiO4 (LSNO) as electrodes were then structured in-situ by shadow-masking. In an attempt to reduce the diffusion of La and Cu and to improve the quality interface with electrode, LSNO was replaced by CaCu3Ru4O12 which was isostructural of CCTO. In a second part, CCTO in the form of pure and doped powder and thin film was studied by electron spin resonance. New results are important to understand the mechanisms giving rise to the high permittivity value
Yang, Fan. "Bruit en 1/f de films minces de manganite La0,7Sr0,3MnO2 pour application en bolométrie / par Fan Yang". Caen, 2005. http://www.theses.fr/2005CAEN2001.
Pełny tekst źródłaCastignolles, Patrice. "Cinétique de la polymérisation radicalaire des acrylates par polymérisation par LASER pulsé et chromatographie d'exclusion stérique multi-détection (PLP-SEC) : analyse critique". Paris 6, 2003. http://www.theses.fr/2003PA066045.
Pełny tekst źródłaFix, Thomas. "Couches minces de Sr2FeMoO6 élaborées par ablation laser pour des jonctions tunnel magnétiques". Université Louis Pasteur (Strasbourg) (1971-2008), 2006. https://publication-theses.unistra.fr/public/theses_doctorat/2006/FIX_Thomas_2006.pdf.
Pełny tekst źródłaWhen two ferromagnetic layers are separated by a thin insulator (or semiconductor), the electronic transport is enabled by tunnelling. This type of stack, called magnetic tunnel junction, is very promising for applications. The magnetoresistance observed in this case is called tunnel magnetoresistance. It is related to the spin polarization of the electrodes, in other words to the asymmetry of the density of states of the electrodes at Fermi energy for the two spin directions. A solution to obtain a higher spin polarization and thus a high magnetoresistance is to use half-metallic ferromagnetic oxides, for which the Fermi energy crosses an energy band for one spin direction and a band gap for the other direction. The challenge is to obtain a half-metal at room temperature. We focus on the half-metal double perovskite Sr2FeMoO6, which offers a relatively high Curie temperature, and is therefore potentially half-metallic at room temperature. The powder synthesis and the thin film deposition by pulsed laser deposition are studied using various techniques. Finally, magnetic tunnel junctions based on Sr2FeMoO6 are grown and the transport properties are examined
Duclere, Jean-René. "Croissance épitaxiale par ablation laser et caractérisations de couches minces du matériau ferroélectrique SrBi2Nb2O2". Rennes 1, 2002. http://www.theses.fr/2002REN10072.
Pełny tekst źródłaPeter, Sandrine. "Etude des mécanismes de la pyrolyse flash et de la pyrolyse laser par spectrométrie de masse : application aux polymères synthétiques et naturels". Metz, 1996. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1996/Peter.Sandrine.SMZ9638.pdf.
Pełny tekst źródłaThe purpose of this work is to compare the flash pyrolysis and the laser ablation/pyrolysis, connected to the gaz chromatography/mass spectrometry (gc/ms). The final aim is to microcharacterize synthetic and natural polymers such as hairs and fibers. After the explanation of the principles and the mechanisms of the thermal pyrolysis, we describe the apparatus involved in this work, in particular pyrolysis ovens, laser pyrolysis device and connections with gc/ms. In order to compare different pyrolysis modes, experimental results are displayed in two manners : characterization of the volatile molecules formed during pyrolysis and the compared study of the different mechanisms occuring in the three pyrolysis methods. First, two synthetic polymers were studied by flash pyrolysis ; the relative proportions of each monomer have been determined. From the results with the organic acids (MALDI), we draw the role of the decarboxilation and of the vaporization of the intact molecule as a function of the wavelength used. The same approach has been made concerning the amino-acids constituting human hair. Then, we have been in order to separate the thermal effects of the laser irradiation from laser desorption. Finally, we applied the three pyrolysis modes to human hair. Comparing the results with the amino-acids and polypeptides analysed in the same conditions, we characterized the pyrolysates from human hair. We identified the mechanisms involved in the breaking of the peptidic chain. For the first time, the laser ablation of a human hair been attempted
Erel, Eric. "Etude et caractérisation de silicates et d'aluminosilicates par spectrométrie de masse couplée à l'ablation laser : Application à la différentiation de gemmes naturelles et synthétiques". Metz, 2003. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2003/Erel.Eric.SMZ0318.pdf.
Pełny tekst źródłaSollier, Arnaud. "Etude des plasmas générés par interaction laser-matière en régime confiné : application au traitement des matériaux par choc laser". Phd thesis, Université de Versailles-Saint Quentin en Yvelines, 2002. http://tel.archives-ouvertes.fr/tel-00089243.
Pełny tekst źródłaAfin de mieux comprendre les phénomènes physiques mis en jeu dans ce régime d'interaction particulier, une modélisation originale du procédé a été développée. Un code numérique traitant les processus de claquage dans l'eau de confinement permet dans un premier temps de déterminer les caractéristiques (intensité crête et durée à mi-hauteur) de l'impulsion laser transmise à travers la fenêtre de confinement. Un modèle hydrodynamique auto-consistant traitant les plasmas confinés (plasmas froids et denses, corrélés et partiellement dégénérés) utilise ensuite ces paramètres pour calculer les chargements mécaniques et thermiques induits à la surface de la cible traitée. Pour terminer, ces chargements sont utilisés en entrée du code aux éléments finis ABAQUS afin de simuler les contraintes résiduelles d'origine mécanique et thermique induites par le traitement.
Les résultats de ces simulations ont été validés par comparaison avec différentes mesures expérimentales réalisées pour des conditions d'irradiation laser (longueurs d'ondes de 1064 nm et de 532 nm, durées d'impulsion de 3 ns et 10 ns) typiques des conditions opératoires réelles utilisées au niveau industriel.
Ces résultats montrent que les petites taches focales permettent de limiter fortement le chauffage de la cible par le plasma confiné, et donc de s'affranchir des effets thermiques induits par le traitement. Ils ouvrent donc de nouvelles perspectives quant à la réalisation du traitement par choc laser sans utiliser de revêtement thermo-protecteur. Par ailleurs, ils permettant d'expliquer les résultats obtenus avec la configuration de traitement développée par Toshiba (très petites taches focales, haute cadence, pas de revêtement protecteur), qui demeuraient incompris jusqu'alors.