The newly discovered iron based superconductors have captivated the attention of the scientific community due to the unusual mechanism behind their superconductivity and their promise as the next generation high temperature superconductors. After a century of superconductor research, the physical mechanism behind high temperature superconductivity is still not understood. These new materials bring renewed hope in elucidating the pairing mechanism responsible with high temperature superconductors and achieving the ultimate goal of the field, room temperature superconductivity. Consequently, a deeper understanding of the intriguing properties of iron based materials is essential. A great deal about the pairing mechanism of Cooper electron pairs can be inferred from the symmetry of their pairing wave function or order parameter. One of the most involved probes for studying the pairing symmetry is the London penetration depth. The low temperature behavior of London penetration depth in superconductors is directly related to the density of states and provides a powerful tool for investigating low-lying quasiparticle energy and, for this very reason, can give valuable hints on superconducting gap symmetry. The work presented focuses on investigating the pairing symmetry in the Fe1+y(Te1−xSex) system using a radio-frequency tunnel diode oscillator (TDO) technique for precise measurements of the temperature dependence of their in-plane penetration depth. The TDO technique, based on an original concept involving the use of planar inductors in an novel configuration, was implemented on a dilution refrigerator to investigate a significant number of single crystal samples, with nominal Se concentrations of 36%, 40%, 43% and 45% respectively, down to temperatures as low as 50 mK. A systematic study together with a comprehensive analysis regarding the order parameter symmetry in the Fe1+y(Te1−xSex) system is presented. In many cases we found that London penetration depth shows an upturn below at low temperatures, indicative of a paramagnetic-type contribution. Also the low-temperature behavior of penetration depth is best described by a quadratic power law with no systematic dependence on the Se concentration. Most importantly, in the limit of T → 0, in some samples we observed a narrow region of linear temperature dependence, suggestive of nodes in the superconducting gap of Fe1+y(Te1−xSex).

Nesta tese desenvolveram-se projetos e modelos de indutores planares para circuitos integrados de radiofrequência nas arquiteturas espiral e cross para as tecnologias CMOS AMS 0,35 ?m e IBM 0,13 ?m, visando representar o desempenho destes na faixa de frequências de corrente contínua até 90% da frequência de ressonância. A modelagem empregada utiliza um circuito elétrico equivalente com nove elementos para representar indutores, para o qual é apresentado um processo para extração dos valores dos seus componentes a partir de dados simulados ou medidos. Foi apresentada uma versão estendida da arquitetura cross original, mais flexível e tratável por algoritmos, com uma indutância 25% maior que a arquitetura espiral de mesma área. Utilizou-se planejamento de experimentos para elaborar conjuntos de amostras de indutores com dimensões geométricas variadas nas arquiteturas e tecnologias estudadas, para os quais desenvolveu-se um conjunto de algoritmos específicos para o projeto dos indutores a partir de suas dimensões. A simulação eletromagnética do layout de cada amostra gerou os resultados empregados no desenvolvimento do processo de extração dos valores dos componentes do circuito equivalente, os quais foram relacionados às dimensões geométricas dos indutores através de equações de projeto elaboradas por meio de análise de regressão multivariada e modelos lineares generalizados. Tanto o processo de extração dos valores dos componentes, como as equações de projeto foram validados estatisticamente pela comparação dos resultados das simulações dos respectivos circuitos equivalentes com os resultados das simulações eletromagnéticas dos layouts dos indutores em cada arquitetura e tecnologia, demonstrando a correspondência entre estes. Discrepâncias observadas em alta frequência entre os resultados de simulação eletromagnética dos indutores e seus respectivos circuitos equivalentes são associados a limitações do modelo de circuito usado, que não considera os fenômenos de correntes de Foucault (correntes de turbilhonamento) e efeito pelicular. O processo de modelagem desenvolvido, devido a sua generalidade, pode ser aplicado ao desenvolvimento de outros modelos de circuito elétrico para indutores, ou mesmo para modelagem de outros componentes passivos para circuitos integrados, como capacitores, resistores e transformadores. / In this thesis were developed designs and models for planar inductors for radiofrequency integrated circuits in the spiral and cross architectures for AMS 0.35 ?m and IBM 0.13 ?m CMOS technologies, aiming to represent the inductors performance in the frequency range of direct current up to 90% of resonant frequency. The employed modeling used an equivalent circuit for inductors with nine elements, for which a process for extracting the values of its components from simulated or measured data is presented. An extended version of the original cross architecture was presented, more flexible and treatable by algorithms, with an inductance 25% larger than the spiral architecture of the same area. Design of experiments was used to elaborate sets of inductor samples with different geometric dimensions in the studied architectures and technologies. Algorithms were developed to design the layout of each inductor considering its architecture and specific dimensions. The layout electromagnetic simulation of each sample generated the results used in the process developed for extracting the values of the components of the equivalent circuit model, which were related to the geometric dimensions of the inductors through design equations elaborated by multivariate regression analysis and generalized linear models. Both the component extraction process and the design equations were statistically validated by comparing the simulation results of the respective equivalent circuit models with the results of the electromagnetic simulations of the inductor layouts in each architecture and technology, demonstrating matching between them. Observed discrepancies at high frequency between the electromagnetic simulation results for the inductors and their respective equivalent circuits are associated with limitations of the circuit model used, which does not consider eddy currents and skin effect phenomena. The modeling process developed, due to its generality, can be applied to the development of other electric circuit models for inductors, or even to model other passive components for integrated circuits, such as capacitors, resistors and transformers.

Nesta tese desenvolveram-se projetos e modelos de indutores planares para circuitos integrados de radiofrequência nas arquiteturas espiral e cross para as tecnologias CMOS AMS 0,35 ?m e IBM 0,13 ?m, visando representar o desempenho destes na faixa de frequências de corrente contínua até 90% da frequência de ressonância. A modelagem empregada utiliza um circuito elétrico equivalente com nove elementos para representar indutores, para o qual é apresentado um processo para extração dos valores dos seus componentes a partir de dados simulados ou medidos. Foi apresentada uma versão estendida da arquitetura cross original, mais flexível e tratável por algoritmos, com uma indutância 25% maior que a arquitetura espiral de mesma área. Utilizou-se planejamento de experimentos para elaborar conjuntos de amostras de indutores com dimensões geométricas variadas nas arquiteturas e tecnologias estudadas, para os quais desenvolveu-se um conjunto de algoritmos específicos para o projeto dos indutores a partir de suas dimensões. A simulação eletromagnética do layout de cada amostra gerou os resultados empregados no desenvolvimento do processo de extração dos valores dos componentes do circuito equivalente, os quais foram relacionados às dimensões geométricas dos indutores através de equações de projeto elaboradas por meio de análise de regressão multivariada e modelos lineares generalizados. Tanto o processo de extração dos valores dos componentes, como as equações de projeto foram validados estatisticamente pela comparação dos resultados das simulações dos respectivos circuitos equivalentes com os resultados das simulações eletromagnéticas dos layouts dos indutores em cada arquitetura e tecnologia, demonstrando a correspondência entre estes. Discrepâncias observadas em alta frequência entre os resultados de simulação eletromagnética dos indutores e seus respectivos circuitos equivalentes são associados a limitações do modelo de circuito usado, que não considera os fenômenos de correntes de Foucault (correntes de turbilhonamento) e efeito pelicular. O processo de modelagem desenvolvido, devido a sua generalidade, pode ser aplicado ao desenvolvimento de outros modelos de circuito elétrico para indutores, ou mesmo para modelagem de outros componentes passivos para circuitos integrados, como capacitores, resistores e transformadores. / In this thesis were developed designs and models for planar inductors for radiofrequency integrated circuits in the spiral and cross architectures for AMS 0.35 ?m and IBM 0.13 ?m CMOS technologies, aiming to represent the inductors performance in the frequency range of direct current up to 90% of resonant frequency. The employed modeling used an equivalent circuit for inductors with nine elements, for which a process for extracting the values of its components from simulated or measured data is presented. An extended version of the original cross architecture was presented, more flexible and treatable by algorithms, with an inductance 25% larger than the spiral architecture of the same area. Design of experiments was used to elaborate sets of inductor samples with different geometric dimensions in the studied architectures and technologies. Algorithms were developed to design the layout of each inductor considering its architecture and specific dimensions. The layout electromagnetic simulation of each sample generated the results used in the process developed for extracting the values of the components of the equivalent circuit model, which were related to the geometric dimensions of the inductors through design equations elaborated by multivariate regression analysis and generalized linear models. Both the component extraction process and the design equations were statistically validated by comparing the simulation results of the respective equivalent circuit models with the results of the electromagnetic simulations of the inductor layouts in each architecture and technology, demonstrating matching between them. Observed discrepancies at high frequency between the electromagnetic simulation results for the inductors and their respective equivalent circuits are associated with limitations of the circuit model used, which does not consider eddy currents and skin effect phenomena. The modeling process developed, due to its generality, can be applied to the development of other electric circuit models for inductors, or even to model other passive components for integrated circuits, such as capacitors, resistors and transformers.

Le développement des dispositifs embarqués visant des applications telles que la téléphonie mobile, l’avionique ou encore les véhicules électriques est en très forte croissance. Les contraintes liées à ces applications sont principalement la réduction du volume, du poids, et ainsi que le coût de production des composants actifs et passifs. C’est ainsi que le Laboratoire Telecom Claude Chappe de l’Université Jean Monnet de Saint Etienne, s’est positionné sur le développement de composants passifs magnétiques dans le but de réduire leur dimension tout en optimisant leur performance. Ce travail de doctorat avait pour but de développer des modèles « type circuit » comportant peu de paramètres pour des composants inductances planaires à couches magnétiques. Les modèles développés doivent prendre en compte les propriétés des couches magnétiques, à savoir la tangente de perte (tanδ) et la perméabilité relative (μr) en fonction de la fréquence, ainsi que les phénomènes haute fréquence : effets de peau et de proximité dans les conducteurs d’une part, couplage capacitif entre spire et entre spires et plan de masse d’autre part. L’étude bibliographique a montré qu’il existe plusieurs modèles d’inductances, avec et sans couche de matériau magnétique. Ces modèles traduisent bien le comportement de l’inductance, mais ne prennent pas en compte certaines propriétés telles que l’évolution de la perméabilité relative et de la tangente de perte en fonction de la fréquence. La simulation nous a permis de mettre au point nos modèles. Nous avons simulé des structures à air, avec une couche de YIG dont la perméabilité relative variait en fonction de la fréquence (avec et sans perte) et enfin des structures à deux couches avec une perméabilité relative et une tangente de perte variable en fonction de la fréquence. Le logiciel nous a également permis de vérifier ainsi le bon comportement des modèles. Afin de valider et de compléter les résultats obtenus en simulation nous avons réalisé les mêmes dispositifs que ceux simulés en utilisant les techniques de micro-électronique. La caractérisation des dispositifs réalisés a été conduite en basse fréquence à l’aide d’un LCRmétre et en haute fréquence à l’aide d’un analyseur vectoriel de réseaux. Les paramètres des modèles ont été obtenus à partir de la simulation ou de la mesure en utilisant un programme d’optimisation. Afin de vérifier l’exactitude des valeurs obtenues, nous avons recalculé les paramètres Yij à partir des éléments extraits et les avons comparés avec les paramètres Yij de mesures ou de simulation. Une bonne corrélation entre les différents paramètres Yij a été constatée sur une large bande de fréquence. Ce travail de thèse a permis de mettre au point trois modèles : modèle d’inductance à air ; modèle d’inductance à une couche et à deux couches tout en prenant en compte les propriétés magnétiques constituant l’inductance / The development of embarked devices used in mobile phone, avionics or electrical vehicles is in very strong growth. Constraints connected to these applications are mainly the reduction of volume, weight and as well as the production cost of the active and passive components. So, Telecom Claude Chappe Laboratory of the Saint Etienne University is positioned on the development of magnetic passive components with the aim of reducing their size while optimizing their performance. This PhD thesis work aimed at developing models "like circuit" containing few parameters for planar inductor components with magnetic layers. The developed models must take into account the magnetic layer properties, as the loss tangent (tanδ) and the relative permeability (μr) according to the frequency, as well as the skin and proximity effects in the conductors, capacity between turn and capacities between turns and ground plan. The bibliographical study showed that there are several inductors models with and without magnetic layer. These models translate well the inductor behavior but do not take into account some properties such as the variation of the loss tangent and the magnetic permeability according to the frequency. The simulation allowed to work out our models. Inductors structures with air, with one magnetic layer and with two magnetic layers when the magnetic permeability and the loss tangent varied according to the frequency have been simulated. The software allowed to verify the good behavior of the models. In order to validate results obtainedin simulation, devices have been realized by using microelectronics techniques. The devices characterization has been carried out at lower frequency by using an LCRmeter and at high frequency by using a vector network analyzer. The model parameters are obtained from simulation and measurement by using an optimization algorithm. To verify the values accuracy, Yij parameters are been recalculated from the extracted parameters and compared with the Yij simulated or measured parameters. A good correlation between everyYij parameters has been noticed on a broad band frequency. This PhD thesis allowed to work out three inductors models: with air, with one magnetic layer, with two magnetic layers while taking into account the magnetic properties constituting the inductor

No description available.

Dans les applications de l’électronique de puissance, les inductances sont généralement utilisées avec des formes d’ondes triangulaire et rectangulaire. Dans ces conditions, les inductances ne peuvent pas être caractérisées avec des formes d’ondes sinusoïdales. Il existe dans la littérature plusieurs méthodes de caractérisation des inductances. Aucune de ces méthodes ne permet de caractériser les composants magnétiques intégrés dans des conditions compatibles avec les formes d’onde de l’électronique de puissance. Une nouvelle méthode de caractérisation en temps réel convenable aux composants magnétiques planaires intégrées est développée dans cette thèse. Le composant sous test est utilisé dans un convertisseur DC-DC. A partir du courant i(t) et de la tension u(t) relevés à ses bornes, il est possible de déterminer la caractéristique φ(i) du composant. Connaissant le cycle d’hystérésis φ(i), les principaux paramètres du composant tels que la valeur de l’inductance, le niveau de saturation du matériau magnétique, les pertes fer peuvent être déterminées. Il convient de préciser qu’après l’enregistrement de u(t) et de i(t), un traitement des données approprié est effectué pour obtenir des signaux exploitables. L’approche a été testée avec succès sur des inductances discrètes et planaires intégrées pour des fréquences de mesure allant jusqu’au MHz. Nous avons ainsi montré que cette méthode permet de relever des cycles mineurs jusqu’à la saturation du matériau magnétique et de tracer l’évolution de l’inductance en fonction de la composante continue du courant. Les résultats montrent que pour de très faibles courants, on a des fortes valeurs de l’inductance qui sont quasiment constantes, en revanche à des courants moyens, l’inductance diminue fortement et à des forts courants, le circuit magnétique se sature et la valeur de l’inductance devient donc très faible. Cette méthode permet également d’étudier l’évolution des pertes fer dans les mêmes conditions d’utilisation que celles rencontrées en électronique de puissance / In applications of power electronics, inductors are generally used with triangular and rectangular waveforms. In these conditions, inductors cannot be characterized with sinusoidal waveforms. Many methods of characterization are developed, but none of them allow the characterization of integrated magnetic components under conditions compatible with power electronics waveforms. A new real-time characterization method suitable for integrated magnetic components is developed in this thesis. The Device under test is inserted in a DC-DC converter. From u(t) voltage and i(t) current recordings, it is possible to determine the φ(i) hysteresis loop that allows main inductor parameters to be determined: inductance value, core losses, and saturation of the magnetic material. It should be made clear when u(t) and i(t) are recorded, suitable signal processing is completed in order to obtain usable signals. The method has been successfully tested on discrete and integrated inductors with measurement frequencies up to MHz. We have thus shown that this method makes it possible to determine minor loops up to the saturation of the magnetic material and to plot the evolution of the inductance versus the DC bias current.The results show that for very low current values, we have obtained strong values of inductor and these values are constant. However, for the mean current, the inductance value decreases drastically and for strong current values, the magnetic material is saturated which causes very small values of inductor. This method also makes it possible to study the evolution of iron losses under the same conditions of use as those encountered in power electronics