This study investigates relaxation polarization in some dielectric components of tester UNISPOT S40 developed by company UNITES Systems a.s. Relaxation polarization in the PCB substrates and in tester’s cable insulation causes undesirable deceleration of some test steps. Relaxation polarization in selected PCB substrates and various cables are examined by method of dielectric relaxation spectroscopy in the frequency domain and by measurement of polarization or depolarization current.

Multifunctional Dielectric Elastomer (DE) devices are well established as actuators, sensors and energy harvesters. Since the invention of the Dielectric Elastomer Switch (DES), a piezoresistive electrode that can directly switch charge on and off, it has become possible to expand the wide functionality of DE structures even more. We show the application of fully soft DE subcomponents in biomimetic robotic structures. It is now possible to couple arrays of actuator/switch units together so that they switch charge between themselves on and off. One can then build DE devices that operate as self-controlled oscillators. With an oscillator one can produce a periodic signal that controls a soft DE robot { a DE device with its own DE nervous system. DESs were fabricated using a special electrode mixture, and imprinting technology at an exact pre-strain. We have demonstrated six orders of magnitude change in conductivity within the DES over 50% strain. The control signal can either be a mechanical deformation from another DE or an electrical input to a connected dielectric elastomer actuator (DEA). We have demonstrated a variety of fully soft multifunctional subcomponents that enable the design of autonomous soft robots without conventional electronics. The combination of digital logic structures for basic signal processing, data storage in dielectric elastomer ip-ops and digital and analogue clocks with adjustable frequencies, made of dielectric elastomer oscillators (DEOs), enables fully soft, self-controlled and electronics-free robotic structures. DE robotic structures to date include stiff frames to maintain necessary pre-strains enabling sufficient actuation of DEAs. Here we present a design and production technology for a first robotic structure consisting only of soft silicones and carbon black.

Dans cette thèse, une étude approfondie sur des matériaux et des solutions pratiques est réalisée afin de répondre aux difficultés rencontrées dans la propagation des ondes à des fréquences térahertz (THz). Deux matériaux ont été identifiés comme étant prometteur: le graphène et le silicium à haute résistivité (HR-Si). Une première solution, basée sur des guides d’ondes à plaques parallèles (parallel plate waveguide-PPWG) avec des conditions de fermetures conducteur parfait (perfect electric conductor-PEC) -- graphène et graphène -- graphène a été analysée dans un premier temps. En considérant l'excitation du graphène par un champ électrique seulement, puis par un champ électromagnétique statique, les équations de Maxwell ont été résolues sous ces deux conditions et les constantes de propagations des différents modes ont été extraites. La démonstration de l'existence d'un mode propagatif hybride à l'intérieur du guide est faite dès que le graphène est excité par un champ magnétique. De plus, il est montré que l'intensité de chaque type de modes, transverse électrique (TE) ou transverse magnétique (TM), peut être ajustée suivant les champs d'excitation du graphène. Bien que le guide à plaques parallèles utilisant du graphène permette d'avoir des propriétés agiles, soit le contrôle des modes selon l'excitation du graphène, il n'en reste pas moins vrai que la faible conductivité intrinsèque au graphène conduit à un problème d'atténuation importante de l'onde. De plus, la difficulté d'obtenir des couches de graphène de taille adéquate entrave le développement de composants et de circuits fonctionnels, utilisables et à un coût raisonnable. La thèse porte ensuite sur l’étude du silicium haute résistivité pour guider des ondes aux fréquences térahertz. Tout d’abord, un guide composé d'une couche de HR-Si, de section rectangulaire dont la largeur est très grande par rapport à la hauteur, est caractérisé en utilisant un système de spectroscopie dans le domaine du temps, système permettant d'obtenir un large spectre de fréquences dans le domaine THz. Par cette caractérisation, les faibles pertes et la faible dispersion du HR-Si est démontrée. Cependant, il est aussi démontré que la géométrie du guide n'est pas optimale, conduisant à des pertes par dispersion de l'onde à l'intérieur du guide au fur et à mesure de sa propagation. Aussi, pour éviter cette dispersion, un confinement de l'onde est proposé en réduisant la largeur de la couche HR-Si pour la rendre de l'ordre de la hauteur (confinement en x et y, propagation en z) conduisant ainsi à la réalisation d'un guide d’ondes diélectrique en ruban (dielectric ribbon waveguide-DRW). Une analyse approfondie de la propagation d'une telle structure a conduit à concevoir un guide à faibles pertes d'une part, mais également à propagation monomode sur une large bande de fréquence. Une méthode de fabrication simple a été développée pour réaliser ce type de guide et un banc de mesure spécifique a été mis en place pour caractériser ce nouveau guide. Les mesures réalisées utilisent un analyseur de réseaux vectoriel (un PNA-X d'Agilent) auquel est branché deux têtes de mesure de la compagnie Virginia Diode Inc's (VDI) pour obtenir les bandes de fréquences désirées. Les sorties sont alors en guide rectangulaire standard, soit WR-8, soit WR-5 selon la plage de fréquence visée. Les résultats des mesures se comparent très bien avec les simulations réalisées avec un logiciel utilisant la méthode des éléments finis en trois dimensions (HFSS de la compagnie ANSYS) permettant d'obtenir les paramètres de la matrice de diffraction (S) mesurée par l'analyseur de réseau vectoriel. Finalement, dans le chapitre 6, un filtre passe-bande est développé comme preuve de concept pour l'utilisation du guide DRW utilisant le matériau HR-Si. Outre les faibles pertes et la propagation monomode d'un tel guide DRW, il est aussi montré dans cette thèse la facilité du processus de fabrication, le faible coût de ce procédé ainsi que la possibilité d'intégration avec d'autres composants passifs et actifs. Avec toutes ces caractéristiques très intéressantes sur différents plans, le guide DRW en HR-Si apparaît comme une solution très compétitive pour devenir un standard dans la bande de fréquence des THz.

De nos jours, l'essor des produits électroniques nomades requièrent une capacité de stockage de données croissante et imposent la fabrication de composants mémoire performants, denses et fiables. Cela implique une grande robustesse des cellules mémoires élémentaires dont les dimensions caractéristiques sont régulièrement réduites. L'objectif principal de la thèse est d'appréhender les mécanismes de claquage d'oxydes minces voire ultraminces intégrés dans des empilements métal/oxyde/semiconducteur. Un intérêt particulier a été porté à la croissance d'îlots cristallins épitaxiés se formant lors de certaines sollicitations électriques et associée aux mécanismes de DBIE (Dielectric Breakdown Induced Epitaxy). L'étude des différents dispositifs (cellules mémoires à grille continue ou discrète, transistors, condensateur) a permis de proposer des corrélations entre la défaillance électrique de ces dispositifs et les défauts microstructuraux générés. Ce travail a été réalisé selon une méthodologie intégrant (i) la sollicitation électrique ; (ii) une préparation d'échantillons adaptée ; (iii) l'identification, l'observation et la caractérisation des défauts par microscopie électronique en transmission (TEM). L'ensemble des études menées a permis d'isoler deux paramètres électriques principaux ayant un rôle prépondérant sur la formation d'îlots de silicium épitaxiés, en lien avec le mécanisme de DBIE : la charge injectée et le courant de compliance. Ces deux paramètres apparaissent comme des facteurs limitant l'emballement thermique qui conduit, en général, à un claquage diélectrique franc de l'oxyde et semblent, par conséquent, retarder la défaillance irréversible d'un dispositif. / Nowadays, the microelectronic industry had to take up ambitious challenges to satisfy the strong economic demand because of the mobile electronic products booming like smartphones, tablets, or more recently "phablets". These high added value products requires the growth of data storage capacity and, subsequently, to produce high-performance, dense and reliable components. That implies a great cell memories robustness whose critical dimensions are regularly reduced. In this context, the thesis issue is to better understand the breakdown mechanisms of the thin and ultra-thin oxides embedded in metal/oxide/semiconductor stacks. Actually, epitaxial growth of crystalline silicon hillocks was pinpointed. These hillocks grown under electrical stresses and were associated to DBIE mechanisms (Dielectric Breakdown Induced Epitaxy). Device studies allowed to correlate electrical stress conditions and microstructural defects thanks to a 3-steps methodology : (i) electrical stresses leading to microstructural defects ; (ii) sample preparation including defect localization and extraction ; (iii) identification, observation and characterization of defects by transmission electron microscopy (TEM). Two main electrical parameters were identified with factors responsible for hillocks growth linked to DBIE : the injected charge and the compliance current. These parameters seem to limit the thermal runaway inducing hard breakdown. Consequently, it is possible that delays the irreversible device degradation. In addition, hillocks seem to grow preferentially under polysilicon grain boundaries over the SiO2/Si stacks.

After nearly 100 years of particle acceleration, particle accelerator experiments continue providing results within the field of high energy physics. Particle acceleration is used worldwide in practical applications such as radiation therapy and materials science research. Unfortunately, these accelerators are large and expensive. Dielectric Laser Acceleration (DLA) is a promising technique for accelerating particles with high acceleration gradients, without requiring large-scale accelerators. DLA utilizes the electric field of a high energy laser to accelerate electrons in the proximity of a nanostructured dielectric surface.The aim of this project was limited to laser beam routing and imaging techniques for a DLA experiment. The goal was to design the laser beam pathway between the laser and the dielectric sample, and testing a proposed imaging system for aiming the laser. This goal was achieved in a test setup using a low-energy laser. In the main setup including a femtosecond laser, the result indicated lack of focus. For a full experimental setup, a correction of this focus is essential and the beam path would need to be combined with a Scanning Electron Microscope (SEM) as an electron source.

Este trabalho de pesquisa apresenta uma nova abordagem para calibrar uma sonda helicoidal TDR, usada para medir o teor de umidade do solo. Foi empregada uma aproximação tomando em consideração a interpretação física dos valores de constantes dielétricas. As equações de calibração foram determinadas mediante um modelo dielétrico misto, quais relacionam a constante dielétrica da mistura multifase com a constante dielétrica e frações de volumes dessas componentes. Ensaios realizados em laboratório permitirem o desenvolvimento de duas equações de calibração para a avaliação de teor de umidade volumétrico e gravimétrico dos solos. A calibração foi executada com medições de constante dielétrica em diferentes líquidos e solos, usando uma sonda convencional TDR e a sonda helicoidal TDR. As leituras realizadas com as duas sondas foram depois comparadas. O modelo dielétrico das duas fases permitiu descrever a contribuição dos materiais dielétricos do corpo da sonda helicoidal e os materiais investigados. Mostrou-se que o conhecimento das características físicas e geométricas da sonda TDR usada nos ensaios é de crucial para garantir a qualidade das constantes dielétricas lidas, e conseqüentemente a determinação do teor de umidade in situ. / The objective of this work was to calibrate a coiled TDR probe used to measure the water content of soil. It was used an approach that takes into account a physical interpretation of the values of the dielectric constants. The calibration equations were determined by means of a mixed dielectric model, which relates the dielectric constant of a multi-phase mixture with the dielectric constants and volume fractions of its components. Tests carried out in the laboratory allowed development of two calibration equations for the assessment of the volumetric and gravimetric soil water content. Calibration was performed with measurements of dielectric constants in different liquids and soils, using a conventional TDR probe and a coiled TDR. The readings performed with the two probes were then compared. The dielectric model of two phases permitted describing the contribution of the dielectric material of the body of the probe coil and the materials investigated. It has been shown that knowledge of the physical and geometrical characteristics of the TDR probe used in the tests is crucial for the quality of the dielectric constant readings, and consequently the determination of water content in situ.

This thesis concerns partial discharge (PD) diagnostics withvariable frequency of applied voltage in the frequency range 1mHz - 400 Hz. The exploration of a new type of spectroscopythat combines partial discharge analysis and dielectricresponse is demonstrated. A question addressed is if and howthe PD activity varies with the frequency of the appliedvoltage. The nature of an existing frequency dependence couldbe useful in the classification of different defects and tojudge the degree of progressive ageing. A Variable-Frequency Phase Resolved Partial DischargeAnalysis (VF-PRPDA) technique is developed for the appliedvoltage frequency range 1 mHz - 400 Hz. The VF-PRPDA techniqueis combined with a system for high voltage dielectricspectroscopy that allows simultaneous measurements. TheVF-PRPDA technique is used for studying the frequencydependence of PD. The PD activity is for example measured byintegrated measures like total charge per cycle and totalnumber of discharges per cycle. Statistical measures like mean,standard deviation, skewness, kurtosis etc. are applied tomeasure the frequency dependence of the phasedistributions. High voltage dielectric spectroscopy is supplemented withharmonic analysis for studying non-linear dielectric responsecurrents. The VF-PRPDA technique is demonstrated on defined objectslike point-plane gaps and artificial voids, but also on aninsulated stator bar and a paper insulated cable. Surfacedischarges on insulating surfaces are studied in an environmentwith a controlled relative humidity and temperature. Theadsorption of moisture on the insulating surface alters thesurface conductivity of the surface and the frequencydependence of the PD activity. The influence of temperature upon the PD activity is studiedfor a oil paper insulated cable. The results of the measurements show that the partialdischarge activity in general is frequency dependent over thefrequency range 1 mHz - 400 Hz. The reasons behind thefrequency dependence are linked to surface- and bulk-conducting mechanisms, frequency dependent field distributionsand statistical effects of the supply of start electrons. An algorithm is developed that relates the phase resolved PDcurrent measured with the PRPDA technique to the non-linearcurrent measured with dielectric spectroscopy. The algorithm isexperimentally verified by simultaneous measurements of PRPDAand dielectric spectroscopy on defined objects. The resultsexplain the contribution of PD to the apparent capacitance andloss. Moreover, the harmonics of the fundamental currentcomponent yield information about, for example, polaritydependent discharge sources. Keywords:diagnostic methods, partial discharges, phaseresolved, variable frequency, dielectric spectroscopy,dielectric response, harmonics, insulation / QC 20100527

THz and mm-wave technology has become increasingly significant in a very diverse range of applications such as spectroscopy, imaging, and communication as a consequence of a plethora of significant advances in this field. However to achieve a mass production of THz systems, all the commercial aspects should be considered. The main concerns are attributed to the robustness, compactness, and a low cost device. In this regard, research efforts should be focused on the elimination of obstacles standing in the way of commercializing the THz technology. To this end, in this study, low cost fabrication technologies for various parts of mm-wave/THz systems are investigated and explored to realize compact, integrated, and rugged components. This task is divided into four phases. In the first phase, a robust fiber-based beam delivery configuration is deployed instead of the free beam optics which is essential to operate the low cost THz photomixers and photoconductive antennas. The compensation of different effects on propagation of the optical pulse along the optical fiber is achieved through all-fiber system to eliminate any bulky and unstable optical components from the system. THz measurements on fiber-coupled systems exhibit the same performance and even better compared to the free beam system. In the next phase, the generated THz wave is coupled to a rectangular dielectric waveguide through design of a novel transition with low insertion loss. The structure dimensions are reported for various range of frequencies up to 650GHz with insertion loss less than 1dB. The structure is fabricated through a standard recipe. In third phase, as consequence of the advent of high performance active device at mm-wave and THz frequency, a transition is proposed for coupling the electromagnetic wave to the active devices with CPW ports. Different approaches are devised for different frequencies as at higher frequencies any kind of metallic structure can introduce a considerable amount of loss to the system. The optimized structures show minimum insertion loss as low as 1dB and operate over 10% bandwidth. The various configurations are fabricated for lower frequencies to verify the transition performance. The last phase focuses on the design, optimization, fabrication and measurements of a new dielectric side-grating antenna for frequency scanning applications. The radiation mechanism is extensively studied using two different commercial full-wave solvers as well as the measured data from the fabricated samples. The optimized antenna achieves a radiation efficiency of 90% and a gain of 18dB. The measured return loss and radiation pattern show a good agreement with the simulation results.

Metal oxides crystallized in perovskite structure are generally modified in two different ways. According to the general structural formula ABO3, the two ways are A-site modification and B-site modification. The primary significance of perovskite metal oxides rests on their importance in electronic devices. A particular class of perovskites, namely Lead Zirconate or modified Lead Zirconate has received a special attention because of their unique antiferroelectricity and various applications in devices. Among the other modifications, A-site modification of PbZrO3 by La is rare and not much explored. Chapter 1 describes various applications of antiferroelectric thin films along with the synthesis and characterization of pure and La modified PbZrO3, which are relevant to the work presented in this thesis. Sol-gel processing and spin coating technique to deposit solid oxide thin films are well known for their low cost of deposition as well as for their ability to achieve better stoichiometric chemical composition. Common crack formation problem of sol-gel grown films can be prevented by ‘drying control chemical adhesive’ like polyvinylpyrrolidone (PVP). Heat treatment of sol-gel derived thin films is generally determined by TGA and DTA. Crystalline phase of deposited solid thin films is determined by XRD whereas effect of modification can be ascertained by XRD peak assignment and relative crystalline peak shifting. Sol-gel grown film thickness is measured by common cross sectional SEM whereas AFM can detail the surface morphology. Chapter 2 summarizes the deposition and characterization of pure and La modified PbZrO3 thin films. Any nonmetal, which is insulator, is dielectric material and show dielectric dispersion in a frequency domain of low field alternative current. Among the most common feature of dielectric dispersion, Maxwell – Wagner type dispersion is well known. Similar kind of dielectric dispersion, named Maxwell – Wagner like dispersion, can be observed while the equivalent circuit consists of parallel G – C along with a series R. Universal power law of ac conductivity is the deciding factor to distinguish the nature of dispersion. Structural phase transition can be determined by dielectric response and it is widely known as dielectric phase transition. Effect of La modification on dielectric phase transition of PbZrO3 thin films depends on stabilization or destabilization of antiferroelectricity. Maximum dielectric constants of pure and modified PbZrO3 thin films depend on the crystallographic orientations of the growth. Chapter 3 presents dielectric properties of pure and La modified PbZrO3 thin films and these properties are correlated to the stabilization or destabilization of antiferroelectricity, relative integrated intensity of (202)O film orientation and trapped electron charge due to oxygen vacancies. Charge storage property of a capacitor is determined by the polarization of the capacitor on application of electric field whereas field dependent integrated area of polarization on withdrawal of electric field determines the recoverable capacitive energy storage. Among the three kinds of capacitors like linear or paraelectric, ferroelectric and antiferroelectric capacitors, antiferroelectric capacitor is known to be best for their ability to store huge amount of recoverable energy. The recoverable energy in antiferroelectrics can be increased by increasing squareness of the P – E hysteresis loop, applicable electric field, polarization or by the all possible combinations of them. Chapter 4 describes the correlation of relative integrated intensity of (202)O [RI(202)O] with critical applied electric field of P – E saturation to provide enhanced squareness of the hysteresis loops. This chapter also describes the variation of charge and recoverable energy storage properties with respect to RI(202)O. Like magnetocaloric effect, electrocaloric effect is capable to alter the temperature of a system by adiabatic polarization or depolarization. From the Maxwell’s relation of thermodynamics, assuming, (∂p ) = (∂s )electrocaloric effect can be calculated from temperature dependent polarization value of a paraelectric, ferroelectric or an antiferroelectric. Chapter 5 presents the electrocaloric effect of pure and La modified PbZrO3 thin films. Summary of present study and discussion have been delineated in Chapter 6 along with the future work which can give more insight into the understanding of antiferroelectric PbZrO3 thin films with respect to Pb and Zr site modification and with respect to different electrodes. (For formulas pl see the pdf file of the thesis)

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