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Ye, Fan. "Surface plasmon polaritons along metal surfaces with novel structures." Thesis, Boston College, 2014. http://hdl.handle.net/2345/bc-ir:103747.
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Thesis advisor: Michael J. NaughtonSurface plasmon polaritons (SPPs) are hybridized quasiparticles of photons and electron density waves. They are confined to propagate along metal-dielectric interfaces, and decay exponentially along the direction perpendicular to the interfaces. In the past two decades, SPPs have drawn intensive attention and undergone rapid development due to their potential for application in a vast range of fields, including but not limited to subwavelength imaging, biochemical/biomedical sensing, enhanced light trapping for solar cells, and plasmonic logic gates. These applications utilize the following intrinsic properties of SPPs: (1) the wavelength of SPPs is shorter (and can be much shorter) than that of free photons with the same frequency; (2) the local electric field intensity associated with SPPs can be orders of magnitude larger than that of free photons; and (3) SPPs are bound to metal surfaces, and are thus easily modulated by the geometry of those surfaces. Here, we present studies on SPPs along metal surfaces with novel structures, including the following: (1) SPP standing waves formed along circular metal surfaces that lead to a "plasmonic halo" effect; (2) directional reflectionless conversion between free photons and SPPs in asymmetric metal-insulator-metal arrays; and (3) broadband absorbance enhancement of embedded metallic nanopatterns in a photovoltaic absorber layer. These works may prove useful for new schemes for SPP generation, plasmon-photon modulation, ultrasensitive dielectric/bio sensing, and high efficiency thin film solar cells
Thesis (PhD) — Boston College, 2014
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
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Takami, Akinori. "Laser induced desorption of molecules from surfaces." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334926.
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Vander, Wielen Lorraine C. "Dielectric barrier discharge-initiated fiber modification." Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/ipstetd-1054/.
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Raghu, Prashant. "Interaction of molecular contaminants with high-k dielectric surfaces." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280445.
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As the device feature size shrinks, films of silicon oxide (SiO₂) will become unsuitable for MOSFET gate dielectric applications and have to be replaced by thicker films of a high-k dielectric material. Among the high-k materials, hafnium oxide (HfO₂) and zirconium oxide (ZrO₂) are the most promising candidates. Molecular contamination can affect the quality of the new gate dielectric films in a manner similar to ultrathin SiO2 films. Therefore, characterization of contaminant adsorption behavior of these high-k films should assist in deciding their potential for successful integration in silicon MOS technology. The interactions of moisture and organic (in particular IPA) contamination with ALCVD(TM) deposited 5-nm HfO₂ and ZrO₂ films were investigated using mass spectrometry. HfO₂ and ZrO₂ were found to have similar moisture adsorption loadings, but significantly higher than that of SiO₂. The new high-k materials also retained a higher portion of the adsorbed moisture after an isothermal nitrogen purge. Almost all the adsorbed moisture could be removed from SiO₂ and HfO₂ after a 300°C bake under nitrogen purge, whereas ZrO₂ surfaces retained significant amounts of the adsorbed moisture. Experiments with ppb-levels of IPA showed that the adsorption loading on the three surfaces had the following order: ZrO₂ > HfO₂ > SiO₂. The relatively slow desorption kinetics of H2O and IPA highlighted the difficulty in removal of these contaminants from HfO₂ and ZrO₂ surfaces. Presence of pre-adsorbed moisture increased IPA adsorption on SiO₂, but reduced adsorption on HfO₂ and ZrO₂. Isotope labeling studies with D₂O showed that IPA reacted with surface hydroxyl groups to form a chemisorbed alkoxy species on all oxides. A multilayer model for adsorption of water and IPA was developed to understand the mechanism of interactions of contaminants with these surfaces. Results indicated that ZrO₂ formed the strongest surface-hydroxyl bond and also physisorbed IPA stronger than HfO₂ and SiO₂. The practical application of the adsorption model is also demonstrated. The results of this work should aid in the selection of the most appropriate dielectric film and design of process/equipment so that it can be more readily integrated into silicon technology.
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Gili, Valerio flavio. "All-dielectric nonlinear nanophotonics." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCD012/document.
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La méta-optique non linéaire tout diélectrique suscite un vif intérêt, grâce à la faisabilité de nanostructures à contraste élevé et indice de réfraction disponible avec la lithographie à semi-conducteurs. Alors que des effets nonlinéaires au troisième ordre ont été rapportés dans les nanoantennes silicium sur isolant, la plate-forme AlGaAs-sur-isolant a récemment permis la démonstration de la génération de la seconde harmonique, dû à la noncentrosymétrie de ce matériel. Cette thèse illustre notre activité récente sur les nanoantennes non linéaires AlGaAs-sur-AlOx, où AlOx est obtenu par attaque chimique sélective par voie humide d'une couche épitaxiale d'AlGaAs riche en aluminium d'une épaisseur de quelques micromètres. Un tel substrat à faible indice de réfraction permet de découpler efficacement les modes nanoantenna de la tranche de GaAs (100) sous-jacent. La thèse présente d'abord les méthodes numériques, expérimentales et technologiques utilisées. Une analyse des résultats obtenus dans la génération de signaux non linéaires dans des nanoantennes simples et dans des structures complexes est ensuite présentée. Tous nos résultats expérimentaux ouvrent la voie à la génération et à la manipulation de signaux non linéaires à l'échelle nanométrique et pointent vers des applications telles que l'holographie non linéaire, la goniométrie sans fond et la vision nocturneAll-dielectric nonlinear meta-optics is attracting a great deal of interest thanks to the feasibility of high refractive-index contrast nanostructures available with semiconductor lithography. While third order nonlinear effects have been reported in silicon-on-insulator nanoantennas, the AlGaAs-on-insulator platform has recently enabled the demonstration of second harmonic generation, owing to the non-centrosymmetry of this material. This PhD thesis illustrates our recent activity on AlGaAs-on-AlOx nonlinear nanoantennas, where AlOx is obtained from selective wet etching of micrometer-thick aluminium-rich AlGaAs epitaxial layer. Such a low refractive index substrate allows to effectively decouple the nanoantenna modes from the underlying GaAs (100) wafer. The thesis first introduces the numerical, experimental and technological methods employed. Afterwards, a review of the results obtained in nonlinear signal generation in single nanoantennas and in complex structures is given. All our experimental results pave the way towards nonlinear signal generation and manipulation at the nanoscale, and point towards applications such as nonlinear holography, background-free goniometry and night vision
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Petrishchev, Vitaly. "Kinetics and Chemistry of Ionization Wave Discharges Propagating Over Dielectric Surfaces." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469100848.
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Iqbal, Asad. "Interaction of Molecular Contaminants with Low-k Dielectric Films and Metal Surfaces." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/196143.
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Ultra low-k dielectric films are expected to widely replace SiO2 as the interlayer dielectric for the next-generation microelectronic devices. A challenge facing the integration of these dielectrics in manufacturing is their interactions with gaseous contaminants, such as moisture and isopropanol, and the resulting change in their properties. Moisture retained in the film not only has detrimental effect on the k value of the film but also causes reliability and adhesion problems due to gradual outgassing. The physical and chemical interactions of moisture with porous spin-on and chemical vapor deposited (CVD) dielectrics are investigated using temperature- and concentration-programmed exposure and purge sequence together with trace moisture analysis, using atmospheric pressure ionization mass spectrometry.The model compounds in this study are porous Methylsilsesquioxane and Black Diamond II films, deposited and treated under typical manufacturing conditions. Transmission Electron Microscope (TEM) studies showed that etching and ashing processes resulted in the formation of two layers, a damaged layer and non-damaged layer, which significantly changed moisture interaction properties.Moisture sorption and desorption studies showed that as compared to SiO2 these films not only have a higher uptake capacity but also a slower and more activated moisture removal process. This could be a significant problem in successful integration of these films in IC manufacturing process.A process model was developed that provided information on the mechanism and kinetics of moisture uptake and release in thin porous films. The model elucidated the effect of film properties on the contamination uptake as well as outgassing. The model is a valuable tool for designing an optimum process for contamination control and removal in porous films.Another concern in IC manufacturing is the outgassing of impurities of electropolished stainless steel (EPSS) surfaces used in UHP gas distribution system. Moisture interaction with EPSS surface is studied in sub ppb range. A fundamental model was developed to study the mechanism and kinetics of moisture uptake and release from EPSS. The model developed would be a valuable tool for designing an optimum process for contamination control and to predict the moisture dry down performance of large-scale, systems.
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Pechereau, François. "Numerical simulation of the interaction of atmospheric pressure plasma discharges with dielectric surfaces." Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00978523.
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In this Ph.D. thesis, we have carried out 2D numerical simulations to study the influence of dielectric surfaces on the propagation dynamics of plasma discharges at atmospheric pressure. First we have improved the computational efficiency of the discharge code used in this work in implementing parallelization techniques and more efficient numerical schemes. Second we have studied the dynamics of an air discharge at atmospheric pressure in a point-to-plane geometry with a dielectric layer on the cathode plane. Then, we have studied the influence of a dielectric layer obstacle in the inter-electrode gap. We have shown that depending on the characteristics of the dielectric layer and the amplitude and polarity of the applied voltage, a second discharge may reignite or not below the dielectric in the second air gap. The comparison of simulation results with experiments has shown that in a point-to-plane geometry with a sharp point and a high over-voltage, a single conical discharge structure is observed. A good agreement on the discharge diameter and propagation velocity has been obtained. With a dielectric obstacle in the gap, the simulated reignition dynamics is faster than in the experiments. To improve the agreement, we have studied the influence of several physico-chemical processes. Finally, we have studied the dynamics of discharges in dielectric tubes at atmospheric pressure. For a He -N2 mixture, we have put forward the importance of three body reactions. Last, the influence of the tube radius on the structure of discharges in He - N2 and air is discussed.
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Bennett, Robert. "Quantum electrodynamic shifts of mass and magnetic moment near dielectric or conducting surfaces." Thesis, University of Sussex, 2013. http://sro.sussex.ac.uk/id/eprint/46447/.
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Quantum electrodynamics is the spectacularly successful theory of the interaction of light and matter. Its consequences are well-understood, and have been experimentally verified to extreme precision. What is not generally known is how these predictions change when the theory is considered in anything other than free space - near a surface, for example. A material boundary causes vacuum fluctuations of the electromagnetic field to be different from their counterparts in free space, causing the electromagnetic environment of a microscopic system sitting near the boundary to differ from that if the surface were not present. This causes a variety of surface-dependent shifts in the properties of the microscopic system - this work investigates these shifts for a free electron. First using explicit normal mode expansion and analytic continuation of the wave-vector in the complex plane, and then using a semi-phenomenological `noise current' approach, the work presents derivations of formulae for the shifts in the mass and magnetic moment of an electron near a dispersive and absorbing surface. The formalism is also extended to the case where the electron is subject to a harmonic potential. It is noted that results for different models of the surface do not agree in the expected limiting cases due to their differing behaviour at low frequency, which leads to the conclusion that one must be very careful to use an appropriate model of a particular surface when considering quantum electrodynamic surface effects. Analysis of the results shows that use of a realistic model of the surface can make these shifts orders of magnitude larger than previous calculations had suggested, since they all relied on the somewhat unrealistic assumption that the surface is perfectly reflecting. This is shown to be particularly relevant to experiments which aim to measure the anomalous magnetic moment of an electron.
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Li, Qin. "Numerical simulations of interactions of electromagnetic waves with lossy dielectric surfaces using fast computational methods /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/5848.
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Boon, Dirk Francois. "The link between daily rainfall and satellite radar backscatter data from the ERS-2 scatterometer in the Free State Province, South Africa." Diss., Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-10272008-132211.
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Joshua, Nihal E. "Direct Immersion Cooling Via Nucleate Boiling of HFE-7100 Dielectric Liquid on Hydrophobic and Hydrophilic Surfaces." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699916/.
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This study experimentally investigated the effect of hydrophobic and hydrophilic surfaces characteristics on nucleate boiling heat transfer performance for the application of direct immersion cooling of electronics. A dielectric liquid, HFE – 7100 was used as the working fluid in the saturated boiling tests. Twelve types of 1-cm2 copper heater samples, simulating high heat flux components, featured reference smooth copper surface, fully and patterned hydrophobic surface and fully and patterned hydrophilic surfaces. Hydrophobic samples were prepared by applying a thin Teflon coating following photolithography techniques, while the hydrophilic TiO2 thin films were made through a two step approach involving layer by layer self assembly and liquid phase deposition processes. Patterned surfaces had circular dots with sizes between 40 – 250 μm. Based on additional data, both hydrophobic and hydrophilic surfaces improved nucleate boiling performance that is evaluated in terms of boiling incipience, heat transfer coefficient and critical heat flux (CHF) level. The best results, considering the smooth copper surface as the reference, were achieved by the surfaces that have a mixture of hydrophobic/hydrophilic coatings, providing: (a) early transition to boiling regime and with eliminated temperature overshoot phenomena at boiling incipience, (b) up to 58.5% higher heat transfer coefficients, and (c) up to 47.4% higher CHF levels. The studied enhanced surfaces therefore demonstrated a practical surface modification method for heat transfer enhancement in immersion cooling applications.
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Sutcliffe, Ronald David. "Aluminum and Copper Chemical Vapor Deposition on Fluoropolymer Dielectrics and Subsequent Interfacial Interactions." Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc279304/.
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Tokarz, Frederick A. "An investigation of dichroic surfaces of staggered tuned arrays in an infinite medium and a stratified dielectric medium /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487676261009385.
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Lin, I.-Ting. "Dielectric elastomer actuators in electro-responsive surfaces based on tunable wrinkling and the robotic arm for powerful and continuous movement." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289711.
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Dielectric elastomer actuators (DEAs) have been used for artificial muscles for years. Recently the DEA-based deformable surfaces have demonstrated controllable microscale roughness, ease of operation, fast response, and possibilities for programmable control. DEA muscles used in bioinspired robotic arms for large deformation and strong force also become desirable for their efficiency, low manufacturing cost, high force-to-weight ratio, and noiseless operation. The DEA-based responsive surfaces in microscale roughness control, however, exhibit limited durability due to irreversible dielectric breakdown. Lowering device voltage to avoid this issue is hindered by an inadequate understanding of the electrically-induced wrinkling deformation as a function of the deformable dielectric film thickness. Also, the programmable control and geometric analysis of the structured surface deformation have not yet been fully explored. Current methods to generate anisotropic wrinkles rely on mechanical pre-loading such as stretching or bending, which complicates the fabrication and operation of the devices. With a fixed mechanical pre-loading, the device can only switch between the flat state and the preset wrinkling state. In this thesis, we overcome these shortcomings by demonstrating a simple method for fabricating fault-tolerant electro-responsive surfaces and for controlling surface wrinkling patterns. The DEA-based system can produce different reversible surface topographies (craters, irregular wrinkles, structured wrinkles) upon the geometrical design of electrode and application of voltage. It remains functional due to its ability to self-insulate breakdown faults even after multiple high voltage breakdowns, and the induced breakdown punctures can be used for amplification of local electric fields for wrinkle formation at lower applied voltages. We enhance fundamental understanding of the system by using different analytical models combined with numerical simulation to discuss the mechanism and critical conditions for wrinkle formation, and compare it with the experimental results from surface topography, critical field to induce wrinkles in films of different thickness, and wrinkling patterns quantitatively analysed by different disorder metrics. Based on the results, we demonstrate its wide applicability in adjustable transparency films, dynamic light-grating filter, molding for static surface patterns, and multi-stable mirror-diffusor-diffraction grating device. For DEAs used for macroscopic-scale deformation in robotic arms, the main issue that undermines the performance of DEA muscles is the trade-off between strong force and large displacement, which limits the durability and range of potential robotic and automation applications of DEA-driven devices. In this thesis, this challenge is tackled by using DEAs in loudspeaker configuration for independent scaling-up of force and displacement, developing a theoretical prediction to optimise the operation of such DEAs in bioinspired antagonistic system to maximise speed and power of the robotic arm, and designing a clutch-gear-shaft mechanical system collaborating with the muscles to decouple the displacement and output force. Therefore, the trade-off between force and displacement in traditional DEA muscles can be resolved. The mechanical system can also convert the short linear spurt to an unlimited rotary motion. Combining these advantages, continuous movement with high output force can be accomplished.
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Jiang, Tingming. "Adsorption of chalcogen-based aromatic organic molecules on metal and dielectric surfaces by self-assembly and molecular beam expitaxy." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS581.
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Dans cette thèse, on a étudié la formation de monocouches auto-assemblées de différentes molécules de chalcogénure et de films minces de semiconducteurs organiques. Leurs caractéristiques électroniques et structurelles ont été étudiées principalement par la spectroscopie de photoélectron à rayons X à base de rayonnement synchrotron, la spectroscopie d’adsorption de rayons X à proximité de seuil, la microscopie à force atomique et la diffraction d'électrons à faible énergie. En outre, les caractéristiques d'adsorption du sélénium et du soufre ont été étudiées comme complément à l'étude des adsorptions des molécules comportant des atomes de chalcogène. Le XPS à haute résolution a été utilisé pour enquêter sur les monocouches auto-assemblées de benzèneselénol et de sélénophène sur Cu (111). L'étude détaillée des pics caractéristiques des niveaux du coeur a démontré l'existence de différents sites d'absorption des molécules et aussi avec les mesures NEXAFS l'apparition du clivage de la liaison Se-C. Ces conclusions sont étayées par l'étude de l’adsorption de sélénium atomique montrant également différents sites d'absorption pour le sélénium atomique avec différents environnements chimiques basés sur une étude XPS haute résolution des spectres caractéristiques Se3d, Se3p et l'imagerie LEED. On a étudié les adsorptions de molécules de polythiophène (nT, n = 1-4, 6) ainsi que pour le α, ω-diquaterthiophène (DH4T) et le dihexylsexithiophène (DH6T) sur les films Au (111) et films de Au sur le mica. Les résultats indiquent que les pics XPS S2p ont des contributions de molécules intactes sur différents sites d'adsorption et des molécules cassées. Ces conclusions sont étayées par les calculs DFT existants. La dissociation spontanée apparaît dans une mesure variable dans différents cas, ce qui pourrait être lié à différentes morphologies de surface, à l'existence de défauts et à la réactivité différentes liés a ces défauts. Des films ultra-minces d'α-sexithiophène (6T) ont été déposés sur des surfaces planes de CaF2 (111) / Si (111) et sur des surfaces striées de CaF2 (110) / Si (001) par épitaxie par faisceau moléculaire. L'image AFM de 6T sur CaF2 (111) montre de grandes îles avec des terrasses plates sans préférence dans le plan, tandis que des îlots étroits et allongés suivant l'ondulation du substrat sont formés pour 6T sur CaF2 (110). Les spectres XPS et NEXAFS indiquent que les interactions entre 6T et les surfaces sont négligeables et que les molécules s'alignent avec leur long axe perpendiculaire aux surfaces pour les deux casIn this thesis, formation of self-assembled monolayers of different chalcogenide molecules and organic semiconductor thin films was investigated. Their electronic and structural characteristics have been investigated primarily by synchrotron based X-ray photoelectron, near edge X-ray absorption fine structure spectroscopy, Atomic force microscopy and low energy electron diffraction. In addition, the adsorption characteristics of selenium and sulfur were studied as a complement to the study of adsorptions of chalcogen headgroup molecules. The high resolution XPS was employed to investigate the self assembled monolayers of benzeneselenol and selenophene on Cu(111). The detailed study of characteristic core level peaks demonstrated the existence of different absorption sites of the molecules and also along with NEXAFS measurements the occurrence of Se-C bond cleavage. These conclusions are supported by the study of atomic selenium adsorptions showing also different absorption sites for the atomic selenium with different chemical environments based on high resolution XPS study of characteristic Se3d, Se3p spectra and LEED imaging. The adsorptions of polythiophene molecules (nT, n=1-4, 6) as well as for α, ω-diquaterthiophene (DH4T) and dihexylsexithiophene (DH6T) on Au(111) and Au films grown on mica was studied. The results indicate that the XPS S2p peaks have contributions from intact molecules on different adsorption sites and broken molecules complemented. These conclusions are supported by existing DFT calculations. Spontaneous dissociation appears to a variable extent in different cases, which could be related to different surface morphologies, existence of defects and ensuing differences reactivity.α-Sexithiophene (6T) ultrathin films were grown on CaF2(111)/Si(111) planar surfaces and on CaF2(110)/Si(001) ridged surfaces by molecular beam epitaxy. The AFM image of 6T on CaF2(111) shows large islands with flat terraces without in-plane preference, while narrow and elongated islands following the substrate corrugation are formed for 6T on CaF2(110). XPS and NEXAFS spectra indicate that the interactions between 6T and surfaces are negligible, and the molecules align with their long axis perpendicular to the surfaces for both cases
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Barrios, Carlos A. "Modified Scanning Probes for the Analysis of Polymer Surfaces." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1249315424.
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Albina, Audrey. "Etude et assemblage d'un condensateur diélectrique hybride utilisant des électrodes de grandes surfaces spécifiques." Toulouse 3, 2006. http://www.theses.fr/2006TOU30101.
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Notre but est d’augmenter la capacité volumique par une méthode originale. Pour ce faire, une nouvelle approche qualifiée d’hybride, inspirée par les techniques de réalisation des électrodes de supercondensateurs et utilisant un matériau isolant, est proposée pour développer de nouveaux condensateurs diélectriques. Les électrodes de supercondensateurs présentent de très grandes surfaces : Elles sont élaborées à partir de nano-matériaux carbonés, conducteurs et poreux tels que le charbon actif et les nanotubes de carbone. La rugosité de ces matériaux offre des surfaces telles que 500 à 2000 m2/g. L’objectif est donc d’associer un isolant présentant une grande rigidité diélectrique à ces électrodes de grandes surfaces spécifiques. Les rugosités de surface que présentent les matériaux carbonés impliquent une répartition inhomogène du champ électrique. Les conditions locales n’étant pas connues, la formule classique de la capacité en fonction de la surface, de la permittivité et de la distance inter-électrodes ne peut plus être appliquée. Nous avons utilisé un logiciel d’éléments finis (FEMLAB) afin de calculer la capacité à partir de la densité d’énergie électrique. La suite de notre travail a consisté à élaborer une structure de condensateur permettant au diélectrique d’exploiter au mieux la surface de l’électrodeOur objective is to increase the capacitance by an original method. It deals with a hybrid approach where two advantages of both systems, the dielectric capacitor and the ultracapacitor, are used. The high geometric aspect of the electrodes of the ultracapacitor and the high dielectric strength of a polymer material are associated. The surface roughness of the electrodes is given by carbonaceous materials (activated carbon and carbon nanotubes). These conductive materials offer high specific surface from 500 to 2000 m2/g. The first part concerns a work of simulation which permits to determine some trends of the influence of an inhomogeneous surface area on the capacitance value. Since the local conditions of electrical field are unknown, the classical analytic formulations of the capacitance cannot be applied. A finite element method is used to calculate the capacitance values from the density of electrical energy. The second and the most important part consists to elaborate the capacitor with the highest capacitance. The final purpose is to improve the electrical energy stored by the capacitor
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Chen, Qianqian. "Synthesis of Photocatalytic Titanium Dioxide and Nitrogen Doped Titanium Dioxide Coatings Using an Atmospheric Dielectric Barrier Discharge." Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/276815.
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In this thesis, we focused on understanding the synthesis of titanium dioxide (TiO2) films and nitrogen doped TiO2 films using an atmospheric pressure Dielectric Barrier Discharge (DBD). The first part of the work was dedicated to the deposition of TiO2 films by cold plasma DBD with titanium tetraisopropoxide as precursor in a single-step process at room temperature. The deposition rate was about 70 nm·min-1. The photocatalytic degradation rate for the degradation of methylene blue (MB) under ultra violet (UV) irradiation of the TiO2 film after annealing was close to a reference anatase TiO2 spin coated film. Moreover, the TiO2 films showed a good photocatalytic stability. The second part of the study focused on the optimization and the understanding of the effect of the plasma parameters (gas flow rate and power) on the morphology of the TiO2 films and on the investigation of the deposition mechanisms. The morphology of the film changed from granular to compact film by either increasing the total flow rate or decreasing the plasma power. In other words, adapting the energy density in the plasma allowed the control of the morphology of the TiO2 films. To our knowledge, it was the first time that the energy density parameters of the plasma were used to control the morphology of TiO2 films. The photocatalytic degradation rate for the degradation of MB under UV irradiation of the annealed TiO2 film turned out to be about 2 and 15 times higher than the one of the commercial TiO2 film and the as-deposited TiO2 films, respectively. In order to extend the light utilization to the visible light range, TiO2 films were doped with nitrogen using a room temperature argon/ammonia plasma discharge. XPS and SIMS results confirmed that the nitrogen has been incorporated in the TiO2 lattice mostly in Ti-N state. This was further confirmed by Raman spectroscopy and XRD. The plasma properties and the doping mechanism were studied by Optical Emission Spectroscopy. It is suggested that the NH radicals played a key role in the doping of TiO2. The concentration of nitrogen in the N-TiO2 coatings could be tuned by adapting the ratio of NH3 in the plasma or the plasma power. The band gap of our N-TiO2 coatings is lower than the one of undoped TiO2 coating. The photocatalytic degradation rate for N-TiO2 coating was more than 4 times higher than the one of the undoped TiO2 coating.Doctorat en Sciences
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Mohamed, Imran. "The application of negative refractive index metamaterials to mm and sub-mm wavelength instrumentation." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/the-application-of-negative-refractive-index-metamaterials-to-mm-and-submm-wavelength-instrumentation(2f650eb9-27bb-4865-81a5-d7f086c6cf22).html.
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The manipulation of electromagnetic radiation via the use of periodic arrays of sub-wavelength metallic structures (unit cells), nowadays named "metamaterials", has been known of in the microwave engineering community for over fifty years. In the last decade interest in such sub-wavelength structures grew, mainly due to their ability to interact with radiation in ways natural materials could not e.g. by producing a negative refractive index (NRI). This project sought to see whether NRI metamaterials could provide benefits to the mm and sub-mm wavelength astronomical instrumentation currently in use. To aid rapid design and optimisation of devices made from a cascaded set of metamaterial unit cells, a hybridised Transmission Line (TL) model was developed where the matrix components used in the TL model were "seeded" with data taken from a Finite Element Method (FEM) model of a simpler structure. A comparison between the two found that the TL model was capable of providing results that differed from the FEM model by no more than ~10E−4 for the transmitted intensity, |S21|^2, and <1° for transmitted phase, arg(S21). A slab of material with a refractive index, n = −1, can exhibit an effect known as "superlensing". A three unit cell thick NRI slab was designed, manufactured and experimentally tested. It was found to be capable of producing an NRI across a fractional band of at least 21%, producing a refractive index value of n = −1 at around 90 GHz. The experimental and simulated transmission and reflection data show good match with each other. A highly birefringent air gap Half Wave Plate (HWP) was designed, manufactured and experimentally tested. Defining its useful bandwidth as the region where the phase difference, is equal to (−180 ± 3)° a single HWP had a fractional bandwidth of 0.3%. The bandwidth was extended by using the Pancharatnam method, developed in the 1950's to produce highly achromatic optical wave plates. The method however is applicable to other frequencies and polarisation control technologies. Optimising a three HWP TL-based Pancharatnam model, the HWP's modelled fractional bandwidth increased to 6.6%. Experimental data agrees with the model showing a plateauing of the phase difference at −180°. A highly birefringent polypropylene embedded Quarter Wave Plate (QWP) was also designed, manufactured and tested. Defining its useful bandwidth as the region where the differential phase is (90 ± 2)° a single QWP produced a fractional bandwidth of 0.6%. By optimising a four QWP TL-based Pancharatnam model, the QWP's performance was improved to 7.8%. Experimental data, whilst not in complete agreement with the model does show a reduction in the gradient of phase difference where it crossed 90°. It was found that current designs for NRI metamaterials fall short of the standards required to be used in quasi-optical astronomical instrumentation due to high dispersion and absorption. The high dispersion limits NRI metamaterials to uses in instruments built for narrowband applications. Whilst the Pancharatnam method can increase bandwidths where a flat differential phase response is required, this comes at the cost of increased absorption. To reach their full potential, NRI metamaterials' lossiness must be reduced e.g. possibly by cryogenic means or the use of "active" metamaterials.
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Dureault, Valérie. "Vieillissement de surfaces d'isolateurs en résine époxy-anhydride : rôles respectifs des UV et du champ électrique." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10003.
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L'objectif principal de l'etude est de determiner les roles respectifs de deux types de contraintes climatiques et electrique dans la phase precoce du vieillissement des isolateurs electriques, en l'absence de decharges electriques detectables. Deux systemes epoxy-anhydride bisphenoliques differents et un systeme cycloaliphatique ont ete etudies. Les resultats obtenus montrent que le vieillissement climatique est domine par la photo-degradation dans le cas des systemes bisphenoliques et par l'hydrolyse dans le cas du systeme cycloaliphatique. L'analyse des fonctions chimiques attaquees et des produits formes a permis l'elaboration des schemas reactionnels de degradation les plus probables. Concernant les proprietes electriques, le vieillissement climatique se traduit par une augmentation de conduction de surface en presence d'eau attribuable a la formation de produits tres hydrophiles. Des phenomenes de vieillissement purement electriques appeles cheminements ont ete observes uniquement dans une atmosphere protegee des uv et de la pluie. Ces phenomenes n'ont par contre jamais ete constates lorsqu'une augmentation de conduction de surface due au vieillissement climatique etait permise. Seules des reactions electrochimiques a l'interface resine-insert sont alors observees. De ces resultats nous avons pu deduire le role-cle joue par l'augmentation de conduction de surface: par ce biais, le vieillissement climatique retarde les manifestations violentes du champ electrique. Cette etude a egalement permis de repousser l'idee d'utiliser les uv pour simuler ou accelerer le vieillissement electrique d'isolateurs. Par contre, l'effet benefique d'une legere conduction de surface pourrait etre utilise pour ameliorer la tenue a long terme des isolations
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Osorio, Ruy Sebastian Bonilla. "Surface passivation for silicon solar cells." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:46ebd390-8c47-4e4b-8c26-e843e8c12cc4.
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Passivation of silicon surfaces remains a critical factor in achieving high conversion efficiency in solar cells, particularly in future generations of rear contact cells -the best performing cell geometry to date. In this thesis, passivation is characterised as either intrinsic or extrinsic, depending on the origin of the chemical and field effect passivation components in dielectric layers. Extrinsic passivation, obtained after film deposition or growth, has been shown to improve significantly the passivation quality of dielectric films. Record passivation has been achieved leading to surface recombination velocities below 1.5 cm/s for 1 Ωcm n-type silicon covered with thermal oxide, and 0.15 cm/s in the same material covered with a thermal SiO2/PECVD SiNx double layer. Extrinsic field effect passivation, achieved by means of corona charge and/or ionic species, has been shown to decrease by 3 to 10 times the amount of carrier recombination at a silicon surface. A new parametrisation of interface charge, and electron and hole recombination velocities in a Shockley-Read-Hall extended formalism has been used to model accurately silicon surface recombination without the need to incorporate a term relating to space-charge or surface damage recombination. Such a term is unrealistic in the case of an oxide/silicon interface. A new method to produce extrinsic field effect passivation has been developed in which charge is introduced into dielectric films at high temperature and then permanently quenched in place by cooling to room temperature. This approach was investigated using charge due to one or more of the following species: ions produced by corona discharge, Na+, K+, Cs+, Mg2+ and Ca2+. It was implemented on both single SiO2 and double SiO2/SiNx dielectric layers which were then measured for periods of up to two years. The decay of the passivation was very slow and time constants of the order of 10,000 days were inferred for two systems: 1) corona-charge-embedded into oxide grown on textured FZ-Si, and 2) potassium ions driven into an oxide on planar FZ-Si. The extrinsic field effect passivation methods developed in this work allow more flexibility in the combined optimisation of the optical properties and the chemical passivation properties of dielectric films on semiconductors. Increases in cell Voc, Jsc and η parameters have been observed in simulations and obtained experimentally when extrinsic field effect passivation is applied to the front surface of silicon solar cells. The extrinsic passivation reported here thus represents a major advancement in controlled and stable passivation of silicon surfaces, and shows great potential as a scalable and cost effective passivation technology for solar cells.
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Kim, Philseok. "Surface modification of nanoparticles for polymer/ceramic nanocomposites and their applications." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31651.
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Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Perry, Joseph W.; Committee Member: Kippelen, Bernard; Committee Member: Lyon, L. Andrew; Committee Member: Marder, Seth R.; Committee Member: Whetten, Robert L. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Ling, Li. "Plasma etching of dielectirc [dielectric] materials using inductively and capacitively coupled fluorocarbon discharges: mechanistic studies of the surface chemistry." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3455.
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Thesis (Ph. D.)--University of Maryland, College Park, 2006.Thesis research directed by: Material Science and Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Vander, Wielen Lorraine C. "Dielectric barrier discharge-initiated fiber modification." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7091.
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Fauché, Pierre. "Plasmonic superradiance in metallo-dielectric nanohybrids." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0281/document.
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Hybridization of quantum emitters and plasmonic nanostructures has attracted much attention over the last years, due to their potential use as plasmon-based nanolasersor to achieve long-range quantum bit entanglement. Recent theoretical studies suggest that the plasmonic field can induce efficient cross-talking between emitters and lead to the formation of collective superradiant states. In this thesis, we developed a theoretical modelable to analyse collective effects in large ensemble of dipoles coupled by an electromagnetic nanoresonator. We experimentally investigated the plasmon-mediated superradiance of organic emitters grafted at a well-controlled distance from a metal nanosphere at room temperature. We report on the measured decay rates of these hybrid structures at the ensemble and single object levels. We find that the decay rate increases i) with the number ofemitters and ii) as the spacing between the emitters and the metal core decreases, a direct and clear evidence of plasmonic superradiance. This trend was observed for two types of hybrid structures, differing both by the size of the metal core and the type of organic dye used as emitter. The observation of plasmonic superradiance at room temperature opens questions about the robustness of these collective states against decoherence mechanisms.This robustness is of major interest for potential applications of quantum systems at room temperaturePlacer des nanostructures plasmoniques à proximité d’émetteurs quantiques est une approche prometteuse pour concevoir des nanolasers plasmoniques ou réaliser l’intrication de bits quantiques à longue distance. Des études théoriques récentes suggèrent que le champ plasmonique peut induire un couplage efficace entre émetteurs et mener à la formationd’états collectifs superradiants. Dans ce travail de thèse, nous avons développé un modèle théorique afin d’analyser les effets collectifs pour un ensemble de dipoles couplés à un nanorésonateur électromagnétique. Nous avons étudié expérimentalement la superradiance plasmonique d’émetteurs organiques greffés à une distance contrôlée d’une nanosphère metallique,à température ambiante. Nous avons mesuré le taux de relaxation de ces structures hybrides, en ensemble et à l’échelle de l’objet unique. Nous observons que le taux de relaxation augmente i) avec le nombre d’émetteurs et ii) lorsque la distance entre les émetteurs et le coeur métallique diminue, une preuve directe et claire de la superradiance plasmonique.Cette tendance a été observée pour deux types de structure hybride, différentes par la taille du coeur métallique et par le type de molécule utilisée comme émetteur. L’observation de la superradiance plasmonique à température ambiante ouvre des questions sur la robustesse d’un état superradiant contre des mécanismes de décohérence. Cette robustesse présente un intérêt majeur pour des applications potentielles de systèmes quantiques à température ambiante
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Nessim, Christine. "Surface modification of powders using dielectric barrier discharges." Thèse, Université de Sherbrooke, 2008. http://savoirs.usherbrooke.ca/handle/11143/1832.
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Le traitement de surface des poudres par plasma hors-équilibre est un outil rapide et indispensable au développement de nouvelles applications pour les poudres traitées. Dans un domaine tel que la synthèse des poudres pyrophoriques métalliques, ou l'ignition est instantanée en cas de non passivation et de contact avec l'air, un traitement par un plasma hors-équilibre permet de modifier les propriétés de surface des poudres afin d'obtenir des poudres moins réactives à basse température tout en gardant leur caractéristique énergétique à haute température. Autre domaine, comme le changement de la mouillabilité des poudres est très recherché. L'objectif de ce travail est de développer des nouvelles techniques pour le traitement de surface des poudres micro ou nanométriques en utilisant les techniques de plasma hors-équilibre. L'avantage de cette approche est de pouvoir modifier les propriétés de surface de ses dites poudres sans affecter les propriétés globales comme par exemple la structure cristalline, taille des poudres et composition chimiques. En fait, les décharges à barrière diélectrique opérant à pression atmosphérique sont idéales pour traiter la surface des poudres sans changer leur structure car ils produisent des electrons énergétiques pour exciter les espèces moléculaires et atomiques à basse température. Aussi, l'opération à pression atmosphérique permet l'integration de l'unité de traitement de surface avec l'unité de synthèse en évitant l'utilisation des systèmes de vide assez dispendieux et difficile à maintenir. Dans ce travail, des expériences sur la déposition ainsi que sur la fonctionnalisation ont été menés en utilisant deux designs de torche à barrière diélectrique. Pour la déposition, des précurseurs tels que l'éthylène, butadiène, pyrrole et acétylène ont été utilisé pour former des couches organiques sur des poudres micro ou nanométriques. D'autres précurseurs à base de silicium comme le tétraéthyloxysilicates ou l'hexaméthyldisiloxane ont été utilisés pour former des dépôts de nature inorganiques ( SiO[indice]x ) ou organiques ( SiO[indice]x C[incice]y H[indice]z ) sur des poudres métalliques ou d'oxydes. Pour les tests de fonctionnalisation, la surface a été modifiée par des décharges, d'hélium-air, hélium-oxygène et hélium-azote. Dans les experiences de déposition, les effets de temps de résidence, de la densité de puissance, de l'injection en mode pulsé ou dans la région après plasma ont été étudié. Quelques tests ont été réalisés pour établir l'effet de la température des gaz et des poudres sur le dépôt. Quand à la fonctionnalisation, l'effet de la densité de puissance, des types de gaz et de temps de résidence ont été examinés. Pour les dépôts réalisés en utilisant des précurseurs organiques ou à base de silicium, l'utilisation de mode pulsé ainsi que l'injection dans la région après plasma ont formé des dépôts dense. Dans la plupart des autres dépôts effectués dans la décharge, des poudres ont été formées. Le faite de chauffer les poudres avant leur injection a augmenté leur dispersion. Finalement, la fonctionnalisation des poudres de polymères ont permis leur mouillabilité pour un débit assez élevé (20g/min) Le vieillissement des poudres n'ont pas dépassé le 25% pour une période de 60 jours dépendamment de leur méthode d'entreposage. Il ressort donc de ce travail que les décharges à barriere diélectriques sont capables de modifier les surfaces des poudres selon les conditions et le design appliqués.
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Croze, Ottavio. "Charged surface interactions in solutions of dielectric macromolecules." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/13502.
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Using a simple mean field model, we have explored how the interactions between charged surfaces are modified when they interact across an electrolytic solution of dielectric spheres, considering these must electrostatically couple to the surfaces. The coupling arises from the intra-surface electric fields, which polarise low permittivity species (oil) dissolved in a high permittivity solvent (water). The model, which already predicts a reduction of surface forces due to the spheres, was extended to describe, more realistically, “dielectric polymers” between surfaces and account for the possibility of depletion. In this case, our results indicate that an account of the coupling between charged surfaces and the polymers modifies both the polymer depletion, the electrostatics and the surfaces forces which result from them. Building on these results, it was possible to adapt a description accounting for coupling to predict phase behaviour of polymer doped smectics. This was contrasted to one which ignores the coupling, as is often assumed in the literature (though some researchers have pointed out the potential effect that polymers could have on the electrostatics of lamellar phases). Our phase diagrams predict that a neglect of coupling is not always a good approximation: particular experimental conditions will lead to qualitatively different phase behaviour between coupled and uncoupled approaches. No consistent investigation of the electrostatic effects just described has been carried out to the best of our knowledge. Since the theory we have developed applies generally to any situation where neutral polymer-like solutes are described in the vicinity of charged surfaces, the relevance of our findings to other interesting experimental situations will be discussed.
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Lin, Ling. "Optical Manipulation Using Planar/Patterned Metallo-dielectric Multilayer Structures." Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/1249.
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Tailoring surface plasmon (SP) resonances using metallic nanostructures for optical manipulation has been widely investigated in recent years; and there are many puzzles yet to be solved in this relatively new area. This thesis covers the study of the interaction of light with SP-supporting planar/patterned metallo-dielectric multilayer structures. Two separate, but closely related subjects were investigated using such structures, which are: SP-assisted optical transmission and optical metamaterials. The physical mechanisms of the SP-assisted transmission phenomenon were studied using planar/grating and planar/hole-array multilayer structures. Extraordinary light transmission has been demonstrated through experimental work and simulations for both arrangements; and the effects of different structural parameters on the transmission efficiencies of the structures were analyzed systematically. The interplays of the surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs) in the extraordinary optical transmission (EOT) phenomenon were identified. The potential of the planar/hole-array multilayer structures as optical magnetic metamaterials was evaluated using two independent electromagnetic simulation techniques. The ability of such structures to produce strong magnetic resonances from infrared down to visible side of spectrum was revealed. The methods of tuning the magnetic response of the structures were suggested. A novel design of optical metamaterial based on high-order multipolar resonances in a single-layer plasmonic structure was also proposed. Numerical results from two different computation methods indicate that a simultaneously negative permittivity and permeability can be achieved in such a structure.
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Kchaou, Marwa. "Influence de la méthode de préparation sur la dynamique de relaxation des polymères en films minces." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1017.
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L'objectif principal de cette thèse est de mettre en évidence l'effet de la méthode de préparation sur la dynamique de relaxation des polymères en films minces. Nous nous sommes focalisés en particulier sur l'importance de la maîtrise du taux d'évaporation du solvant lors de la préparation des films, en termes de contrôle de la magnitude des contraintes résiduelles et les conséquences engendrées sur les propriétés physiques. Dans un premier temps, nous exposons la problématique de déviation des propriétés de polymères en films minces et le lien avec la technique de préparation. Nous décrivons un moyen simple permettant de contrôler le taux d'évaporation du solvant en ajustant la concentration de la solution et la vitesse de rotation de la tournette. Les expériences de démouillage nous ont permis de suivre l'effet du taux d'évaporation du solvant sur les propriétés viscoélastiques des polymères près de la Tg. Les résultats obtenus sur des films minces de polystyrène mettent en évidence le rôle de la méthode de préparation sur la probabilité de rupture des films, les temps caractéristiques de relaxation, la dynamique de démouillage et la magnitude des contraintes résiduelles. Dans une seconde partie, nous présentons également une expérience basée sur la propagation des fissures dans les films minces vitreux. Une simple observation microscopique, ainsi que des imageries en AFM permettent de prouver le rôle du taux d'évaporation du solvant lors de la préparation. Enfin, nous explorons une nouvelle approche expérimentale portant sur la possibilité d'investigations en temps réel et lors de démouillage la relaxation moléculaire des chaînes dans les films minces par des mesures diélectriques directes. Nous avons réussi à prouver non seulement un rôle de la méthode de préparation des films mais également que la restauration du comportement du polymère en volume « bulk » est possible en fonction du temps quelques soient les paramètres du film. Nous confirmons ainsi que les propriétés anormales observées dans les films minces spin-coatés sont dictées par l'état métastable provoqué par la méthode de préparationThe aim of this work is to highlight the influence of the sample preparation on the relaxation dynamics of supported polymer thin films. We focus in particular on the importance of tuning the solvent evaporation rate during films preparation, in terms of controlling the magnitude of residual stresses, and the impact on the physical properties. Firstly, we expose the deviation of the polymer behavior in thin polymer films related to the preparation technique. Then, we describe how the solvent evaporation rate can be precisely tuned by varying the concentration of the solution and the rotation rate of the spin coater. Dewetting experiments allowed us to investigate the effect of the solvent evaporation rate on the viscoelastic behavior of the polymers near the Tg. The probability of films rupture, the characteristic time, dewetting dynamics and the magnitude of residual stresses are deduced to prove the impact of sample preparation. In the second part, we present cracks propagation experiments in glassy thin films. A simple microscopic observation, as well as AFM imaging are used to emphasize the role of the solvent evaporation rate during the preparation. Finally, we present a new experimental approach to investigate in real time and during dewetting the dynamics of polymers in thin films by direct dielectric measurements. We have successfully proved not only the impact of sample preparation but also the restoration of the bulk behavior of polymers is possible during the time whatever the film parameters. We therefore confirm that the anomalous properties observed in spin-coated films are governed by the metastable state induced by the sample preparation
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Bleckmann, Felix [Verfasser]. "Controlling surface plasmon polaritons with dielectric nanostructures / Felix Bleckmann." Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/1124540326/34.
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Heinisch, Rafael Leslie [Verfasser]. "Surface electrons at dielectric plasma walls / Rafael Leslie Heinisch." Greifswald : Universitätsbibliothek Greifswald, 2013. http://d-nb.info/1043793488/34.
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Mathew, Anoop. "Interfacial phenomena in high-kappa dielectrics." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 118 p, 2009. http://proquest.umi.com/pqdweb?did=1654501721&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Dahal, Arjun. "Surface Science Studies of Graphene Interfaces." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5820.
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Interfaces between graphene and dissimilar materials are needed for making devices, but those interfaces also modify the graphene properties due to charge transfer and/or symmetry breaking. In this dissertation we investigate the technology of preparing graphene on different substrates and how the substrate influences the electronic properties of graphene.
Synthesizing large area graphene on late transition metals by chemical vapor deposition is a promising approach for many applications of graphene. Among the transition metals, nickel has advantages because the good lattice match and strong interaction between graphene/Ni(111) enables the synthesis of a single domain of graphene on Ni(111). However, the nickel substrate alters the electronic structure of graphene due to substrate induced symmetry breaking and chemical interaction of the metal d-band with graphene. Similar chemical interactions are observed for other transition metals with a d-band close to the Fermi-level. On the other hand, graphene mainly physisorbs on transition metals with a lower lying d-band center. In this thesis we investigate the growth of graphene on nickel by vacuum chemical vapor deposition (CVD). In particular, we present our studies of graphene synthesis on Ni(111) substrates. We demonstrate the self-limiting monolayer of single domain of graphene can be grown on single crystal Ni(111). Our studies also show that selective twisted bilayer graphene can be grown by carbon segregation on Ni(111)-films. To modify the interaction between graphene and the nickel substrate we investigated the intercalation of tin. In the case of graphene physisorbed on weakly interacting metals, some charge doping of graphene occurs due to work function differences between graphene and the metal. Using x-ray photoemission spectroscopy (XPS) we correlate the charge doping of graphene on different metals with the C-1s binding energy. This study demonstrate that XPS can be used to determine the Fermi-level in graphene. While metal intercalation can alter the interaction with the substrate it does not avoid overlap of electronics states at the Fermi-level. Therefore a band gap material should be inserted between the graphene and the metal growth substrate (in this case Pt(111)). This is accomplished by oxidation of intercalated iron at elevated oxygen pressure. We demonstrate that a 2D-FeO layer can be formed in between graphene and the Pt(111) surface. We discuss the role of the 2D-FeO moiré-structure on the nanoscale electronic properties of graphene.
To date good quality graphene can only be grown by CVD on late transition metals. To obtain graphene on other substrates the graphene can be transferred mechanically from a growth substrate to various other materials. We demonstrate that this transfer can also be achieved to tungsten, an early transition metal that easily forms a carbide. In our studies to avoid oxidation of the tungsten substrate and reaction of the graphene with the tungsten substrate under thermal treatment, protection of the W(110) surface with sulfur has been explored.
For the integration of graphene into device architectures, graphene has to be interfaced with high-κ dielectrics. However, because of the inert nature of graphene, most high-κ do not wet graphene and thus preventing formation of contiguous dielectric layers. Yttrium oxide (Y2O3) has been demonstrated to be an exception and we characterized the growth of Y2O3 on various metal supported graphene and graphene transferred to SiO2. We showed that such a Y2O3 layer can also act as seeding layer for the growth of alumina, which is the preferred dielectric material in many applications. Finally, we investigate the charge doping of graphene in a metal/graphene/dielectric stack and find that the charge doping of graphene is a function of both the work function of the metal as well as the covering dielectric. Thus the dielectric layer can modify the charge doping of graphene at a metal contact.
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Hasegawa, Keisuke. "The effect of geometry and surface morphology on the optical properties of metal-dielectric systems /." Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2008. http://hdl.handle.net/1794/8581.
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Thesis (Ph. D.)--University of Oregon, 2008.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 127-133). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.
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Kjelgaard, Khin. "Radiation-induced desorption and surface modification in dielectric single crystal materials." Online access for everyone, 2004. http://www.dissertations.wsu.edu/Dissertations/Fall2004/K%5FKjelgaard%5F110204.pdf.
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Tillin, Martin David. "Dielectric response of metals using optically excited surface plasmon-polaritons." Thesis, University of Exeter, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236520.
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Martini, David M. "Metallization and Modification of Low-k Dielectric Materials." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9754/.
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Aluminum was deposited onto both Teflon AF and Parylene AF surfaces by chemical vapor deposition of trimethylaluminum. This work shows that similar thin film (100 Angstroms) aluminum oxide adlayers form on both polymers at the low temperature dosing conditions used in the studies. Upon anneal to room temperature and above, defluorination of the polymer surfaces increased and resulted in fluorinated aluminum oxide adlayers; the adlayers were thermally stable to the highest temperatures tested (600 K). Angle-resolved spectra showed higher levels of fluorination toward the polymer/adlayer interface region. Copper films were also deposited at low temperature onto Teflon AF using a copper hexafluoroacetylacetonate-cyclooctadiene precursor. Annealing up to 600 K resulted in the loss of precursor ligands and a shift to metallic copper. As with aluminum adlayers, some polymer defluorination and resulting metal (copper) fluoride was detected. Parylene AF and polystyrene films surfaces were modified by directly dosing with water vapor passed across a hot tungsten filament. Oxygen incorporation into polystyrene occurred exclusively at aromatic carbon sites, whereas oxygen incorporation into parylene occurred in both aromatic and aliphatic sites. Oxygen x-ray photoelectron spectra of the modified polymers were comparable, indicating that similar reactions occurred. The surface oxygenation of parylene allowed enhanced reactivity toward aluminum chemical vapor deposition. Silicon-carbon (Si-Cx) films were formed by electron beam bombardment of trimethylvinylsilane films which were adsorbed onto metal substrates at low temperatures in ultra-high vacuum. Oxygen was also added to the films by coadsorbing water before electron beam bombardment; the films were stable to more than 700 K, with increasing silicon-oxygen bond formation at elevated temperatures. Copper metal was sputter deposited in small increments onto non-oxygenated films. X-ray photoelectric spectra show three-dimensional copper growth (rather than layer-by-layer growth), indicating only weak interaction between the copper and underlying films. Annealing at elevated temperatures caused coalescence or growth of the copper islands, with spectra indicating metallic copper rather than copper oxide.
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Erman, Marko. "L'éllipsométrie spectroscopique à haute résolution latérale : modélisation, application aux surfaces, interfaces et puits quantiques dans le matériaux semi-conducteur III-V." Paris 6, 1986. http://www.theses.fr/1986PA066400.
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Etude théorique et expérimentale de l'application de la méthode aux semi-conducteurs III-V et en particulier à l'analyse des interfaces. Etude des systèmes GaAlAs/GaAs et GaInAs/InP. Détermination simultanée de l'épaisseur des couches et de l'énergie de localisation pour les différentes transitions optiques, dans le cas de puits quantiques et de super-réseaux; effets dus au couplage entre les puits quantiques. Obtention de cartographies avec une résolution optique de 10mu m. Le traitement théorique des images ellipsométriques est base sur le concept de trajectoires.
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Mechaik, Mehdi Mohamad 1963. "Surface wave propagation on a perforated ground plane with dielectric coating." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277877.
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In this thesis, the surface wave propagation along a periodically perforated conducting ground plane with dielectric coating has been studied for frequencies low enough for the ground plane to be approximated accurately by two bonded wire arrays. The field components have been obtained by using the z-directed electric and magnetic Hertz potentials which greatly simplify the application of the boundary conditions at the interfaces. The application of the appropriate boundary conditions on both sides of the plane of the wire mesh has resulted in a doubly infinite system of equations which, when truncated, can be solved for the wire currents and the propagation characteristics of the surface wave supported by the perforated ground plane. The plane is then modeled by a tensor impedance matrix relating the tangential components of the electric field to the components of the current density in the plane of the mesh. It has been shown that the surface wave propagation constant and the impedance matrix do not significantly depend on the direction of propagation for electrically small wire spacings. For such cases, it is shown that the components of the electric field can be directly related to the second order derivatives of the components of the current density flowing along the perforated ground plane.
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McPhee, Graeme. "Surface-Bound Plasmonic and Leaky Electromagnetic Modes of Metal-Dielectric Structures." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517370.
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Wilde, Nicholas David. "Optimization of surface dielectric barrier discharge ion sources for electroaerodynamic propulsion." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127106.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 33-34).
Surface dielectric barrier discharges (SDBDs) are a type of asymmetric dielectric barrier discharge (DBD) that can be used to generate ions and produce aerodynamic forces in air. They have been studied for aerodynamic flow control and proposed for small aircraft propulsion as both direct sources of thrust and as ion sources for "decoupled" electroaerodynamic (EAD) propulsion, in which decoupling ionization from ion-acceleration provides performance and control advantages. SDBDs can also be integrated into aircraft surfaces without introducing additional drag. A challenge for these aerospace applications is minimizing the power draw (or maximizing the efficiency) of these actuators. Optimizing SDBD actuators requires a robust model for SDBD electrical power draw as a function of geometric, material, and electrical properties.
Existing approaches use empirical power law fits to estimate the power of a specific DBD configuration at certain electrical operating points; they are challenging to use in engineering design and optimization as they require experimental measurements for each individual configuration. This thesis proposes the first physics-based model for surface DBD power consumption. The proposed model is based on established models for parallel-plate or "volume" DBDs, and it incorporates the effect of changing plasma length that is specific to SDBDs. This thesis examines SDBDs of three materials, eleven thicknesses, and 394 unique electrical operating points and finds a correlation with R² = 0.99 (n = 394) between experimentally-measured power and model-predicted power. SDBD power measurements extracted from four other experiments from the literature are analyzed with a correlation of R² = 0.97 (n = 101), demonstrating that the model is generalizable to other SDBD constructions.
Ionization rate is also measured to facilitate optimization for use in decoupled EAD thrusters. This work enables the quantitative design and optimization of SDBDs for EAD propulsion and other applications in aerospace and beyond.
by Nicholas David Wilde.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics
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Stanfield, Scott Alan II. "A SPECTROSCOPIC INVESTIGATION OF A SURFACE-DISCHARGE-MODE, DIELECTRIC BARRIER DISCHARGE." Wright State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=wright1261582116.
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Seidelmann, Lukas Josef Wilfried. "Atmospheric pressure dielectric barrier discharges for the surface modification of polypropylene." Thesis, Manchester Metropolitan University, 2015. http://e-space.mmu.ac.uk/608794/.
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Polypropylene films are widely used as packaging materials for foodstuffs, since they offer excellent barrier properties against polar substances, high elasticity, mechanical strength, transparency and chemical stability. However, the relatively low surface energy of polypropylene represents a major issue for the adhesion of printing inks and labels. To improve printability it is necessary to perform a surface activation process. In the presented work, the atmospheric pressure dielectric barrier discharge (DBD) in nitrogen is investigated as a surface treatment method to increase the surface energy of biaxially orientated polypropylene foils. This technology creates a non-thermal plasma by applying strong electrical fields to a gas between two electrodes. The reactive species of the plasma forms new electronegative chemical groups on the surface and also etches the surface of the substrate. Both effects lead to an increase of the surface energy of the plasma treated polymer films. The crosslinking of polymer chains is also a possible effect caused by the plasma treatment. A new plasma rig was designed for this project, including a closed plasma chamber, two different parallel electrode configuration (flat or sawtooth electrodes) and a reel-to-reel system for the transport of the polypropylene foil. The designed system allows to adjust the sizes of the gas gap and the thickness of the dielectric. In addition, the plasma chamber can be filled with every gas or gas mixture wanted. A D-optimal design of experiments approach was utilised to study the influence of the power applied to the electrodes, the size of the gas gap and the thickness of the dielectric on the wettability of the treated polymer films. Furthermore, a flat electrode and a sawtooth electrode configuration are compared to each other. The findings of this work clearly indicate that the sawtooth electrode configuration is superior regarding the consumed electrical power and the wettability of the treated films. The optimal setting for the plasma treatment with the sawtooth electrode configuration are a low gas gap and a high power applied to the electrodes. The thickness of the dielectric has no influence on the wettability of the treated film. However, the increase of the dielectric thickness leads to an increase of the consumed power. These findings were transferred to an industrial process, where the polymer foils were treated in a nitrogen atmosphere with admixtures of CO2, N2O and C2H2 in the ppm range under the founded optimal conditions. A significant difference in the surface energies of these samples could not be identified by contact angles measurement, but all samples showed a significantly reduced hydrophobic recovery rate in comparison to samples treated by the in the industry more conventional plasma treatment in air. The DBD surface treatment in nitrogen is therefore an important improvement for the industrial production, because the treated packaging foils can be stored longer before they are processed further without the need to refresh the surface treatment. The low hydrophobic recovery of the samples treated in the nitrogen plasma is connected to an intensified crosslinking of the polymer chains on the surface of the treated polypropylene films.
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Ceballos, Sanchez Oscar. "Stabilité thermique de structures de type TiN/ZrO2/InGaAs." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY027/document.
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Les semiconducteurs composés III-V, et en particulier l’InGaAs, sont considéréscomme une alternative attractive pour remplacer le Silicium (Si) habituellement utilisépour former le canal dans les dispositifs Métal-Oxide-Semiconducteur (MOS). Sa hautemobilité électronique et sa bande interdite modulable, des paramètres clés pourl’ingénierie de dispositifs à haute performance, ont fait de l’InGaAs un candidatprometteur. Cependant, la stabilité thermique et la chimie des interfaces desdiélectriques high-k sur InGaAs est beaucoup plus complexe que sur Si. Tandis que laplupart des études se concentrent sur diverses méthodes de passivation, telles que lacroissance de couches passivantes d’interface (Si, Ge, et Si/Ge) et/ou le traitementchimique afin d’améliorer la qualité de l’interface high-k/InGaAs, les phénomènes telsque la diffusion d’espèces atomiques provenant du substrat dus aux traitementsthermiques n’ont pas été étudiés attentivement. Les traitements thermiques liés auxprocédés d’intégration de la source (S) et du drain (D) induisent des changementsstructurels qui dégradent les performances électriques du dispositif MOS. Unecaractérisation adaptée des altérations structurelles associées à la diffusion d’élémentsdepuis la surface du substrat est importante afin de comprendre les mécanismes defaille. Dans ce travail, une analyse de la structure ainsi que de la stabilité thermiquedes couches TiN/ZrO2/InGaAs par spectroscopie de photoélectrons résolue en angle(ARXPS) est présentée. Grâce à cette méthode d’analyse non destructive, il a étépossible d’observer des effets subtils tels que la diffusion d’espèces atomiques àtravers la couche diélectrique due au recuit thermique. A partir de la connaissance dela structure des couches, les profils d’implantation d’In et de Ga ont pu être estiméspar la méthode des scenarios. L’analyse de l’échantillon avant recuit thermique apermis de localiser les espèces In-O et Ga-O à l’interface oxide-semiconducteur. Aprèsrecuit, les résultats démontrent de façon quantitative que le recuit thermique cause ladiffusion de In et Ga vers les couches supérieures. En considérant différents scénarios,il a pu être démontré que la diffusion d’In et de Ga induite par le recuit atteint lacouche de TiO2. Dans le cas où l’échantillon est recuit à 500 °C, seule la diffusion d’Inest clairement observée, tandis que dans le cas où l’échantillon est recuit à 700 °C, onobserve la diffusion d’In et de Ga jusqu’à la couche de TiO2. L’analyse quantitative~ viii ~montre une diffusion plus faible de Gallium (~ 0.12 ML) que d’Indium (~ 0.26 ML) à 700°C /10 s. L’analyse quantitative en fonction de la température de recuit a permisd’estimer la valeur de l’énergie d’activation pour la diffusion d’Indium à travers leZircone. La valeur obtenue est très proche des valeurs de diffusion de l’Indium àtravers l’alumine et l’hafnia précédemment rapportées. Des techniquescomplémentaires telles que la microscopie électronique en transmission à hauterésolution (HR-TEM), la spectroscopie X à dispersion d’énergie (EDX) et laspectrométrie de masse à temps de vol (TOF-SIMS) ont été utilisés pour corréler lesrésultats obtenus par ARXPS. En particulier, la TOF-SIMS a révélé le phénomène dediffusion des espèces atomiques vers la surfaceIII-V compound semiconductors, in particular InGaAs, are considered attractivealternative channel materials to replace Si in complementary metal-oxidesemiconductor(MOS) devices. Its high mobility and tunable band gap, requirementsfor high performance device design, have placed InGaAs as a promising candidate.However, the interfacial thermal stability and chemistry of high-k dielectrics on InGaAsis far more complex than those on Si. While most studies are focused on variouspassivation methods, such as the growth of interfacial passivation layers (Si, Ge, andSi/Ge) and/or chemical treatments to improve the quality of high-k/InGaAs interface,phenomena such as the out-diffusion of atomic species from the substrate as aconsequence of the thermal treatments have not been carefully studied. The thermaltreatments, which are related with integration processes of source and drain (S/D),lead to structural changes that degrade the electrical performance of the MOS device.A proper characterization of the structural alterations associated with the out-diffusionof elements from the substrate is important for understanding failure mechanisms. Inthis work it is presented an analysis of the structure and thermal stability ofTiN/ZrO2/InGaAs stacks by angle-resolved x-ray photoelectron spectroscopy (ARXPS).Through a non-destructive analysis method, it was possible to observe subtle effectssuch as the diffusion of substrate atomic species through the dielectric layer as aconsequence of thermal annealing. The knowledge of the film structure allowed forassessing the In and Ga depth profiles by means of the scenarios-method. For the asdeposited sample, In-O and Ga-O are located at the oxide-semiconductor interface. Byassuming different scenarios for their distribution, it was quantitatively shown thatannealing causes the diffusion of In and Ga up to the TiO2 layer. For the sampleannealed at 500 °C, only the diffusion of indium was clearly observed, while for thesample annealed at 700 °C the diffusion of both In and Ga to the TiO2 layer wasevident. The quantitative analysis showed smaller diffusion of gallium (~ 0.12 ML) thanof indium (~ 0.26 ML) at 700 °C/10 s. Since the quantification was done at differenttemperatures, it was possible to obtain an approximate value of the activation energyfor the diffusion of indium through zirconia. The value resulted to be very similar topreviously reported values for indium diffusion through alumina and through hafnia.~ vi ~Complementary techniques as high resolution transmission electron microscopy (HRTEM),energy dispersive x-ray spectroscopy (EDX) and time of flight secondary ion massspectrometry (TOF-SIMS) were used to complement the results obtained with ARXPS.Specially, TOF-SIMS highlighted the phenomenon of diffusion of the substrate atomicspecies to the surface
Compuestos semiconductores III-V, en particular InxGa1-xAs, son consideradosmateriales atractivos para reemplazar el silicio en estructuras metal-oxidosemiconductor(MOS). Su alta movilidad y flexible ancho de banda, requisitos para eldiseño de dispositivos de alto rendimiento, han colocado al InxGa1-xAs como uncandidato prometedor. Sin embargo, la estabilidad térmica en la interfazdieléctrico/InxGa1-xAs es mucho más compleja que aquella formada en la estructuraSiO2/Si. Mientras que la mayoría de los estudios se centran en diversos métodos depasivación tales como el crecimiento de las capas intermedias (Si, Ge y Si/Ge) y/otratamientos químicos para mejorar la calidad de la interfaz, fenómenos como ladifusión de las especies atómicas del sustrato como consecuencia del recocido no hansido cuidadosamente estudiados. Los tratamientos térmicos, los cuales estánrelacionados con los procesos de integración de la fuente y el drenador (S/D) en undispositivo MOSFET, conducen a cambios estructurales que degradan el rendimientoeléctrico de un dispositivo MOS. Una caracterización apropiada de las alteracionesestructurales asociadas con la difusión de los elementos del substrato hacia las capassuperiores es importante para entender cuáles son los mecanismos de falla en undispositivo MOS. En este trabajo se presenta un análisis de la estructura y laestabilidad térmica de la estructura TiN/ZrO2/InGaAs por la espectroscopía defotoelectrones por rayos X con resolución angular (ARXPS). A través de un método deanálisis no destructivo, fue posible observar efectos sutiles tales como la difusión delas especies atómicas del sustrato a través del dieléctrico como consecuencia delrecocido. El conocimiento detallado de la estructura permitió evaluar los perfiles deprofundidad para las componentes de In-O y Ga-O por medio del método deescenarios. Para la muestra en estado como se depositó, las componentes de In-O yGa-O fueron localizadas en la interfaz óxido-semiconductor. Después del recocido, semuestra cuantitativamente que éste causa la difusión de átomos de In y Ga hacia a lascapas superiores. Asumiendo diferentes escenarios para su distribución, se muestraque el recocido provoca la difusión de In y Ga hasta la capa de TiO2. Para la muestrarecocida a 500 °C, se observó claramente la difusión de indio, mientras que para lamuestra recocida a 700 °C tanto In y Ga difunden a la capa de TiO2. El análisis~ iv ~cuantitativo mostró que existe menor difusión de átomos de galio (0.12 ML) que deindio (0.26 ML) a 700 °C/10 s. Puesto que el análisis sobre la cantidad de materialdifundido se realizó a diferentes temperaturas, fue posible obtener un valoraproximado para la energía de activación del indio a través del ZrO2. El valor resultóser muy similar a los valores reportados previamente para la difusión de indio a travésde Al2O3 y a través de HfO2. Con el fin de correlacionar los resultados obtenidos porARXPS, se emplearon técnicas complementarias como la microscopía electrónica detransmisión (TEM), la espectroscopía de energía dispersiva (EDX) y la espectrometríade masas de iones secundarios por tiempo de vuelo (SIMS-TOF). Particularmente, TOFSIMSdestacó el fenómeno de difusión de las especies atómicas sustrato hacia lasuperficie
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Tsuchiya, Kenji, Hitoshi Okubo, Tsugunari Ishida, Naoki Hayakawa, and Hiroki Kojima. "Development Process of Impulse Surface Flashover on Alumina Dielectrics in Vacuum." IEEE, 2011. http://hdl.handle.net/2237/20729.
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MISHRA, AWANISH KUMAR. "DESIGN OF A NOVEL SAPPHIRE BASED DIELECTRIC RESONATOR TO MEASURE THE SURFACE RESISTANCE OF HIGH TEMP SUPER CONDUCTORS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1061222730.
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Innes, R. A. "Surface plasmon-polaritons and thermally-induced optical nonlinearities in liquid crystals." Thesis, University of Exeter, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380733.
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Shieh, Kuen-Wey. "Least-squares electromagnetic analysis of thin dielectrics using surface equivalence." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/NQ53725.pdf.
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Hickey, Michael A. "Reduced surface-wave twin arc-slot antennas on electrically thick dielectric substrates." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58794.pdf.
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