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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
601

Implantação iônica de baixa energia em polímero para desenvolvimento de camadas compósitas nanoestruturadas condutoras litografáveis. / Low energy ion implantation into polymers to develop conductive composite layers for lithography.

Teixeira, Fernanda de Sá 28 June 2010 (has links)
Eletrônica utilizando polímero em substituição ao silício é uma área de pesquisa recente com perspectivas econômicas promissoras. Compósitos de polímeros com partículas metálicas apresentam interessantes propriedades elétricas, magnéticas e ópticas e têm sido produzidos por uma grande variedade de técnicas. Implantação iônica de metais utilizando plasma é um dos métodos utilizados para obtenção desses compósitos condutores. Neste trabalho é realizada implantação de íons de ouro de baixa energia em PMMA utilizando plasma. O PMMA tem grande importância tecnológica sendo largamente utilizado como resiste em litografias por feixe de elétrons, raios-X, íons e deep-UV. Como resultado da implantação iônica de baixa energia em PMMA há formação de uma camada nanométrica de material condutor. Esse novo material, denominado compósito isolante-condutor, permite criar micro e nanodispositivos através de técnicas largamente utilizadas em microeletrônica. Medidas elétricas são realizadas in situ em função da dose de íons metálicos implantada, o que permite um estudo das propriedades de transporte desses novos materiais, que podem ser modeladas pela teoria da percolação. Simulações utilizando o programa TRIDYN permitem obter a profundidade e o perfil da implantação dos íons. São mostradas caracterizações importantes tais como Microscopia Eletrônica de Transmissão, Microscopia de Varredura por Tunelamento, Espalhamento de Raios-X a Baixos Ângulos, Difração de Raios-X e Espectroscopia UV-vis. Essas técnicas permitem visualizar e investigar o caráter nanoestruturado do compósito metal-polímero. Ainda como parte deste projeto, as camadas condutoras formadas no polímero são caracterizadas quanto à manutenção das suas características de elétron resiste. / Electronics using polymers instead of silicon is a recent research area with promising economic perspectives. Polymer with metallic particles composites presents interesting electrical, magnetic and optical properties and they have been produced by a broad variety of techniques. Metal ion implantation using plasma is one of the used methods to obtain conductor composites. In this work it is performed low energy gold ion implantation in PMMA by using plasma. PMMA has great technological importance once it is broadly used as resist in electron-beam, X-ray, ion and deep UV lithography. As a result of low energy ion implantation in PMMA, a nanometric conducting layer is formed. This new material, named insulator-conductor composite, can allow the creation of micro and nanodevices through well known microelectronics techniques. Electrical measurements are performed in situ as a function of metal ions implanted dose, which allows the investigation of electrical transport of these new materials, which can be modeled by the percolation theory. Simulations using TRIDYN computer code provide the prediction of depth profile of implanted ions. Important characterizations are showed such as Transmission Electron Microscopy, Scanning Tunneling Microscopy, Small Angle X-Ray Scattering, X-Ray Diffraction and UV-vis Spectroscopy. These techniques allow to visualize and to investigate the nanostructured character of the metal-polymer composite. Still as a part of this project, the conducting layers formed are characterized in relation to the maintenance of their characteristics as electron-beam resist.
602

Implantação iônica de baixa energia em polímero para desenvolvimento de camadas compósitas nanoestruturadas condutoras litografáveis. / Low energy ion implantation into polymers to develop conductive composite layers for lithography.

Fernanda de Sá Teixeira 28 June 2010 (has links)
Eletrônica utilizando polímero em substituição ao silício é uma área de pesquisa recente com perspectivas econômicas promissoras. Compósitos de polímeros com partículas metálicas apresentam interessantes propriedades elétricas, magnéticas e ópticas e têm sido produzidos por uma grande variedade de técnicas. Implantação iônica de metais utilizando plasma é um dos métodos utilizados para obtenção desses compósitos condutores. Neste trabalho é realizada implantação de íons de ouro de baixa energia em PMMA utilizando plasma. O PMMA tem grande importância tecnológica sendo largamente utilizado como resiste em litografias por feixe de elétrons, raios-X, íons e deep-UV. Como resultado da implantação iônica de baixa energia em PMMA há formação de uma camada nanométrica de material condutor. Esse novo material, denominado compósito isolante-condutor, permite criar micro e nanodispositivos através de técnicas largamente utilizadas em microeletrônica. Medidas elétricas são realizadas in situ em função da dose de íons metálicos implantada, o que permite um estudo das propriedades de transporte desses novos materiais, que podem ser modeladas pela teoria da percolação. Simulações utilizando o programa TRIDYN permitem obter a profundidade e o perfil da implantação dos íons. São mostradas caracterizações importantes tais como Microscopia Eletrônica de Transmissão, Microscopia de Varredura por Tunelamento, Espalhamento de Raios-X a Baixos Ângulos, Difração de Raios-X e Espectroscopia UV-vis. Essas técnicas permitem visualizar e investigar o caráter nanoestruturado do compósito metal-polímero. Ainda como parte deste projeto, as camadas condutoras formadas no polímero são caracterizadas quanto à manutenção das suas características de elétron resiste. / Electronics using polymers instead of silicon is a recent research area with promising economic perspectives. Polymer with metallic particles composites presents interesting electrical, magnetic and optical properties and they have been produced by a broad variety of techniques. Metal ion implantation using plasma is one of the used methods to obtain conductor composites. In this work it is performed low energy gold ion implantation in PMMA by using plasma. PMMA has great technological importance once it is broadly used as resist in electron-beam, X-ray, ion and deep UV lithography. As a result of low energy ion implantation in PMMA, a nanometric conducting layer is formed. This new material, named insulator-conductor composite, can allow the creation of micro and nanodevices through well known microelectronics techniques. Electrical measurements are performed in situ as a function of metal ions implanted dose, which allows the investigation of electrical transport of these new materials, which can be modeled by the percolation theory. Simulations using TRIDYN computer code provide the prediction of depth profile of implanted ions. Important characterizations are showed such as Transmission Electron Microscopy, Scanning Tunneling Microscopy, Small Angle X-Ray Scattering, X-Ray Diffraction and UV-vis Spectroscopy. These techniques allow to visualize and to investigate the nanostructured character of the metal-polymer composite. Still as a part of this project, the conducting layers formed are characterized in relation to the maintenance of their characteristics as electron-beam resist.
603

Litografiskt Allehanda 1859-1865 : Konsten att skapa ett album för svensk konst

Lidman, Charlotte January 2016 (has links)
The aim of my thesis is to study the release and the project of Litografiskt Allehanda, an art magazine covering contemporary Swedish art and artists, published from 1859 to 1865. My purpose is to look at the choice of the published material for Litografiskt Allehanda, the influence the contributing artists, how the work with advertisement and subscriptions was made and if it fulfilled its own purpose. Through a social and communicative perspective I am studying the relations between the different actors like the publicists, the artists, the subscribers and also the interaction between the lithographs and the texts.  Litografiskt Allehanda was the first successful lithographic work produced in Sweden, and the release lasted for six years. The printer and lithographer Axel Jacob Salmson, who was the founder of the magazine, led the printing work for two years before Sigfrid Flodin, a bookseller, took over and continued the work for another four years. The idea with Litografiskt Allehanda was to reach out to people all over Sweden and give everyone an opportunity to enjoy art, something that usually was exclusively for the upper class in the big cities. The analysis shows that there were people in smaller cities that subscribed to the magazine and also that the amount increased every year. Every volume contained 48 lithographic posters with a diversity of genres, from portraits and landscapes to some with more ethnographic character and ancient Nordic motives. The content became more Swedish with every year and letters show that the participating artists had quite a big influence over the published material. Every poster was accompanied by a text, which didn’t necessary had anything to do with the image, but was meant to create some entertainment for the reader. Some of these essays were written by special authors, while some were written by the artists themselves. Even if Litografiskt Allehanda is mentioned in almost every reference as being of great importance for the development of lithography and its proliferation in Sweden, there is nothing written that is just about the magazine.
604

Nanolithographie par sonde locale catalytique : une approche bottom-up pour la nanostructuration de surfaces organominérales / Catalytic scanning probe lithography : a bottom-up approach allowing the nanostructuration of organomineral surfaces

Botton, Julien 17 December 2015 (has links)
Face à la quête constante de miniaturisation, les nanosciences ont connu un essor fulgurant lors de la dernière décennie. Au sein de ces dernières, les procédés lithographiques – clé de voûte de l’industrie des semi-conducteurs – permettent désormais d’accéder à des nanomatériaux fonctionnels. Malgré les récents développements technologiques, l’obtention de nanostructures possédant une résolution inférieure à 100 nm reste un défi majeur pour la communauté scientifique.Devant l’intérêt grandissant de développer des méthodes alternatives en nanolithographie, notre groupe s’est tourné vers une approche chimique, nommée nanolithographie par sonde locale catalytique (cSPL). Combinant la robustesse de la catalyse organométallique et la flexibilité offerte par la microscopie à sonde locale, notre stratégie permet la nanostructuration de surfaces organominérales par la création de liaisons covalentes dans des conditions douces. Cette approche innovante constitue le premier exemple d’immobilisation d’un catalyseur homogène à la surface d’une pointe d’un microscope à force atomique (AFM), dans l’optique de contrôler spatialement une réactivité chimique, l’époxydation localisée d’alcènes terminaux. Ces fonctions époxydes ont été employées comme points d’ancrage dans la nanostructuration à façon de surfaces de silicium avec une large variété de nucléophiles. De plus, l’optimisation des paramètres physico-chimique influant sur la réaction, a permis d’atteindre des résolutions latérales de l’ordre de 40 nm et laisse entrevoir de nombreuses perspectives dans la nanostructuration tridimensionnelle de matériaux organiques. / In regard to the constant quest for miniaturization, the field of nanosciences has known a tremendous expansion over the last decade. More precisely, lithographic technologies - key processes for the semi-conductor industry – allow to access to functional nanomaterials. Despite recent technological developments, the synthesis of nanostructures with a sub-100 nm resolution remains a major challenge for the scientific community.Due to the growing interest in the design of new nanolithographic methods, our group has focused its efforts on the development of a chemical approach, named catalytic scanning probe lithography (cSPL). Unifying the robustness of organometallic catalysis and the flexibility offered by scanning probe microscopy, our strategy allows the nanostructuration of organomineral surfaces in a soft controlled manner by the formation of covalent bonds. This innovative approach represents the first example of the immobilization of an homogeneous catalyst on the edge of an atomic force microscope (AFM) tip, in order to spatially control a chemical reaction: the localized epoxidation reaction of terminal alkenes. Those epoxides were then used as anchoring sites, in the nanostructuration of silicon wafers with a broad range of nucleophiles. Moreover, the different physico-chemical parameters influencing the reaction were optimized, allowing us to reach lateral resolutions down to 40 nm and opening new perspectives in the field of 3D-nanostructuration of organic materials.
605

Etude du tissage de filaments de très faibles diamètres : conception d'une machine de micro tissage / Study of very small diameter filaments weaving : design of a micro weaving machine

Farra, Fadi 21 December 2009 (has links)
Le but du travail est de montrer la faisabilité du tissage de filament de très faible diamètre (de l'ordre de 10 à 25 -tm) et de matières différentes (cuivre, or, polyester...). Les essais du comportement mécanique (traction, fatigue) du micro filament de cuivre ont montré la possibilité du tissage de ce type du filament à cette échelle. A partir de ces résultats, il est possible d'entrevoir des solutions techniques de tissage pour réaliser des tissus à partir de ces filaments. Ce travail a permis donc de concevoir les différentes parties de la machine de micro tissage : système d'alimentation des fils de chame, système de formation de la foule, système d'insertion du fil de trame, système de mouvement du peigne, système d'appel et de stockage du tissu. Le système de formation de la foule de type Jacquard représente le cœur de la machine à tisser. Il lève un verrou technologique persistant depuis de très nombreuses années. Les résultats prometteurs des micros actionneurs fluidiques ont permis de montrer la faisabilité du micro tissage. Ils ont permis également de valider le procédé de la fabrication d'un bloc des plusieurs actionneurs capable de séparer les filaments de chaîne pour former la foule. Le logiciel de contrôle et de dessin conçu permet à la fois de réaliser des armures et de les compiler en format convenable pour pouvoir les transmettre à la carte de contrôle. Cette dernière permet de contrôler les différentes parties de la machine à tisser. / The aim of this work is to demonstrate the feasibility ofweaving filaments of very small diameter (about 10 to 25 -tm) made ofvarious materials (copper, gold, polyester, etc...). The possibility of weaving copper micro filaments at this scale has been proved via the fatigue and traction mechanical tests. According to these results, it was possible to foresee weaving technical solutions to produce fabrics from these micro filaments. This work has permitted the design of the different parts of the micro weaving machine: warp let-off system, warp shedding system, filling insertion system, beat-up system and take-up system. Warp shedding system of Jacquard type represents the heart of the weaving machine. It solved the complicated technical problem ofweaving materials that persists since many years. The positive results of micro fluidic actuators have demonstrated the feasibility of micro weaving. They have also validated the process of manufacturing a block of severa! actuators capable of separating the warp filament's to form the shed. The created software of control and design allows to make weaves and to compile them into a convenient format to be transmitted to the control card. This card controls the different parts of the weaving machine.
606

Lithographie par division de pas de réseau pour les circuits logiques avancés / Lithography pitch division network for advanced logic circuits

Moulis, Sylvain 20 November 2014 (has links)
Aujourd'hui, les outils de lithographie utilisés dans l'industrie arrivent à leur limite de résolution en simple exposition. Pour continuer à diminuer les dimensions, il faut utiliser des techniques de double exposition, mais cela entraîne une explosion des coûts de fabrication. Cette thèse se focalise sur les aspects de modélisation de deux techniques, Sidewall Image Transfer et Directed Self-Assembly, qui sont pressenties pour permettre à l'industrie de continuer la réduction des dimensions des transistors, tout en minimisant les coûts. / Today, the lithographic tools used in industry came to their resolution limit in single patterning. In order to continue the reduction of dimensions, it is necessary to use double patterning, but this increase drastically the cost of manufacturing. This thesis focus on the modelisation aspects of two techniques, Sidewal Image Transfer and Directed Self-Assembly, that can help the industry continuing making transistors even smaller, while keeping the costs manageable.
607

Two-Dimensional Photonic Crystals in InP-based Materials

Mulot, Mikaël January 2004 (has links)
Photonic crystals (PhCs) are structures periodic in thedielectric constant. They exhibit a photonic bandgap, i.e., arange of wavelengths for which light propagation is forbidden.Engineering of defects in the PhC lattice offers new ways toconfine and guide light. PhCs have been manufactured usingsemiconductors and other material technologies. This thesisfocuses on two-dimensional PhCs etched in InP-based materials.Only recently, such structures were identified as promisingcandidates for the realization of novel and advanced functionsfor optical communication applications. The primary focus was on fabrication and characterization ofPhC structures in the InP/GaInAsP/InP material system. Thedemands on fabrication are very high: holes as small as100-300nm in diameter have to be etched at least as deep as 2µm. Thus, different etch processes had to be explored andspecifically developed for InP. We have implemented an etchingprocess based on Ar/Cl2chemically assisted ion beam etching (CAIBE), thatrepresents the state of the art PhC etching in InP. Different building blocks were manufactured using thisprocess. A transmission loss of 10dB/mm for a PhC waveguide, areflection of 96.5% for a 4-row mirror and a record qualityfactor of 310 for a 1D cavity were achieved for this materialsystem. With an etch depth of 4.5 µm, optical loss wasfound to be close to the intrinsic limit. PhC-based opticalfilters were demonstrated using (a) a Fabry-Pérot cavityinserted in a PhC waveguide and (b) a contra-directionalcoupler. Lag effect in CAIBE was utilized positively to realizehigh quality PhC taper sections. Using a PhC taper, a couplingefficiency of 70% was demonstrated from a standard ridgewaveguide to a single line defect PhC waveguide. During the course of this work, InP membrane technology wasdeveloped and a Fabry-Pérot cavity with a quality factorof 3200 was demonstrated. Keywords:photonic crystals, photonic bandgap materials,indium phosphide, dry etching, chemically assisted ion beametching, reactive ion etching, electron beam lithography,photonic integrated circuits, optical waveguides, resonantcavities, optical filtering, finite difference time domain,plane wave expansion.
608

Functional Tissue Engineering of Myocardium Through Cell Tri-culture

Iyer, Rohin 22 August 2012 (has links)
Cardiac tissue engineering promises to create therapeutic tissue replacements for repair of diseased native myocardium. The main goals of this thesis were four-fold: 1) to evaluate cardiac tissues engineered using multiple cell types including endothelial cells (EC), fibroblasts (FB), and cardiomyocytes (CM); 2) to spatiotemporally track cells in organoids and optimize their seeding percentages for improved function; 3) to enhance vascular cord formation through sequential versus simultaneous seeding of ECs and FBs; and 4) to perform mechanistic studies to elucidate the role of soluble factors in cell-cell communication. Microscale templates fabricated from photocrosslinkable poly(ethylene glycol) diacrylate (PEG-DA) were used for all studies for rapid screening. When ECs and FBs were precultured for two days prior to seeding enriched CMs, cells self-assembled into three-dimensional, beating organoids, compared to simultaneously tricultured EC/ FB / CM which formed non-contractile clusters. Fluorescent dyes were used to label and track each cell type for up to 4 days, demonstrating an even distribution of cells within precultured organoids versus EC clustering in simultaneous triculture. When ECs were seeded first, followed by FBs 24 hours later and CMs 48 hours later, vascular-like cords formed that persisted with time in a seeding density-dependent manner. Vascular endothelial growth factor (VEGF) signaling was quantified, showing higher endogenous VEGF secretion rates in sequential preculture (16.6 ng/mL/hr) compared to undetectable VEGF secretion in simultaneous triculture. Blocking of endogenous VEGF signaling through addition of VEGF antibody / VEGFR2 inhibitor resulted in a significant decrease in mRNA and protein expression of the key cardiac gap junctional marker connexin-43. These findings provide a foundation for future work into the mechanisms governing functional cardiac tissue engineering performance and may aid in the development of novel therapies for heart failure based on growth factor signaling and engineering of vascularized, clinically relevant cardiac tissue patches.
609

Functional Tissue Engineering of Myocardium Through Cell Tri-culture

Iyer, Rohin 22 August 2012 (has links)
Cardiac tissue engineering promises to create therapeutic tissue replacements for repair of diseased native myocardium. The main goals of this thesis were four-fold: 1) to evaluate cardiac tissues engineered using multiple cell types including endothelial cells (EC), fibroblasts (FB), and cardiomyocytes (CM); 2) to spatiotemporally track cells in organoids and optimize their seeding percentages for improved function; 3) to enhance vascular cord formation through sequential versus simultaneous seeding of ECs and FBs; and 4) to perform mechanistic studies to elucidate the role of soluble factors in cell-cell communication. Microscale templates fabricated from photocrosslinkable poly(ethylene glycol) diacrylate (PEG-DA) were used for all studies for rapid screening. When ECs and FBs were precultured for two days prior to seeding enriched CMs, cells self-assembled into three-dimensional, beating organoids, compared to simultaneously tricultured EC/ FB / CM which formed non-contractile clusters. Fluorescent dyes were used to label and track each cell type for up to 4 days, demonstrating an even distribution of cells within precultured organoids versus EC clustering in simultaneous triculture. When ECs were seeded first, followed by FBs 24 hours later and CMs 48 hours later, vascular-like cords formed that persisted with time in a seeding density-dependent manner. Vascular endothelial growth factor (VEGF) signaling was quantified, showing higher endogenous VEGF secretion rates in sequential preculture (16.6 ng/mL/hr) compared to undetectable VEGF secretion in simultaneous triculture. Blocking of endogenous VEGF signaling through addition of VEGF antibody / VEGFR2 inhibitor resulted in a significant decrease in mRNA and protein expression of the key cardiac gap junctional marker connexin-43. These findings provide a foundation for future work into the mechanisms governing functional cardiac tissue engineering performance and may aid in the development of novel therapies for heart failure based on growth factor signaling and engineering of vascularized, clinically relevant cardiac tissue patches.
610

Quantum Coherence Effects in Novel Quantum Optical Systems

Sete, Eyob Alebachew 2012 August 1900 (has links)
Optical response of an active medium can substantially be modified when coherent superpositions of states are excited, that is, when systems display quantum coherence and interference. This has led to fascinating applications in atomic and molecular systems. Examples include coherent population trapping, lasing without inversion, electromagnetically induced transparency, cooperative spontaneous emission, and quantum entanglement. We study quantum coherence effects in several quantum optical systems and find interesting applications. We show that quantum coherence can lead to transient Raman lasing and lasing without inversion in short wavelength spectral regions--extreme ultraviolet and x-ray--without the requirement of incoherent pumping. For example, we demonstrate transient Raman lasing at 58.4 nm in Helium atom and transient lasing without inversion at 6.1 nm in Helium-like Boron (triply-ionized Boron). We also investigate dynamical properties of a collective superradiant state prepared by absorption of a single photon when the size of the sample is larger than the radiation wavelength. We show that for large number of atoms such a state, to a good approximation, decays exponentially with a rate proportional to the number of atoms. We also find that the collective frequency shift resulting from repeated emission and reabsorption of short-lived virtual photons is proportional to the number of species in the sample. Furthermore, we examine how a position-dependent excitation phase affects the evolution of entanglement between two dipole-coupled qubits. It turns out that the coherence induced by position-dependent excitation phase slows down the otherwise fast decay of the two-qubit entanglement. We also show that it is possible to entangle two spatially separated and uncoupled qubits via interaction with correlated photons in a cavity quantum electrodynamics setup. Finally, we analyze how quantum coherence can be used to generate continuous-variable entanglement in quantum-beat lasers in steady state and propose possible implementation in quantum lithography.

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