• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 333
  • 53
  • 44
  • 40
  • 17
  • 17
  • 12
  • 11
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 670
  • 161
  • 116
  • 88
  • 86
  • 63
  • 56
  • 55
  • 50
  • 50
  • 45
  • 41
  • 41
  • 41
  • 39
  • 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.
261

Toward sub-10 nm lithographic processes: epoxy-based negative tone molecular resists and directed self-assembly (DSA) of high χ block copolymers

Cheng, Jing 20 September 2013 (has links)
It’s becoming more and more difficult to make smaller, denser, and faster computer chips. There’s an increasing demand to design new materials to be applied in current lithographic process to get higher patterning performance. In this work, the aqueous developable single molecule resists were introduced, synthesized and patterned. A new group of epoxide other than glycidyl ether, cyclohexene oxide was introduced to functionalize a molecular core and 15 nm resolution was obtained. The directed self-assembly (DSA) of block copolymers as an alternative lithographic technique has received growing interest in the last several years for performing higher levels of pitch subdivision. A 3-step simplified process for DSA by using a photodefinable substrate was introduced by using a functionalized polyphenol with an energy switchable group and a crosslinkable group. Two high χ block copolymers PS-b-PAA and PS-b-PHEMA were successfully designed and synthesized via ATRP with controlled Mw and PDI. The size of the same PS-b-PAA polymer was tunable by varying the thermal annealing time. PS-b-PHEMA shows to be a suitable block polymer for the industry-friendly thermal annealing process. A self-complementary hydrogen-bonding urea group as a center group was used to facilitate the self-assembly of polymers. “Click” chemistry is promising for synthesis of PS-Urea-Urea-PMMA.
262

Carbon nanotubes and graphene polymer composites for opto-electronic applications

Boulanger, Nicolas January 2016 (has links)
Carbon nanotubes are carbon based structures with outstanding electronical and mechanical properties. They are used in a wide range of applications, usually embedded in polymer in the form of composites, in order to affect the electronic behavior of the matrix material. However, as the nanotubes properties are directly dependent on their intrinsic structure, it is necessary to select specific nanotubes depending on the application, which can be a complicated and inefficient process. This makes it attractive to be able to reduce the amount of material used in the composites. In this thesis, focus is placed on the electrical properties of the composites. A simple patterning method is presented which allows the use of extremely low amounts of nanotubes in order to increase the electrical conductivity of diverse polymers such as polystyrene (PS) or poly(3-hexylthiophene) (P3HT). This method is called nanoimprint lithography and uses a flexible mold in order to pattern composite films, leading to the creation of conducting nanotube networks, resulting in vertically conducting samples (from the bottom of the film to the top of the imprinted patterns). In parallel, X-ray diffraction measurements have been conducted on thin P3HT polymer films. These were prepared on either silicon substrate or on graphene, and the influence of the processing conditions as well as of the substrate on the crystallinity of the polymer have been investigated. The knowledge of the crystalline structure of P3HT is of great importance as it influences its electronic properties. Establishing a link between the processing conditions and the resulting crystallinity is therefore vital in order to be able to make opto-electronic devices such as transistor or photovoltaic cells.
263

All-Polymer Based Fabrication Process for an All-Polymer Flexible and Parellel Optical Interconnect

Yang, Jilin January 2015 (has links)
This thesis proposed and demonstrated a new all-polymer based fabrication process for an all-polymer flexible and parallel optical interconnect cable having a vertical light coupler, which can not only cut down the cost by eliminating metallization process for alignment but also facilitate both in production and application. Throughout the process, polyimide was used as the substrate, coated by Epoclad as claddings, then AP2210B and WPR 5100 were used to fabricate waveguides and 45 degree mirror couplers, respectively. In addition, precisely aligned mirror couplers to waveguides are fabricated by using polymer-based, non-metallic, and transparent alignment marks. Conventional and metallic alignment marks are easy to be detected by camera, when a layer of high reflective material, generally Cr metal, is patterned. However, transparent polymer material is used in this process, as alignment marks made of it which are actually buried phase structures. Therefore, it is hardly to be observed by conventional microscopy system. Hence, to increase the contrast of the alignment marks, I proposed and tested a feature specific alignment camera system for which the shape and depth of the alignment marks are optimized for phase-based imaging, such as phase contrast and Schlieren imaging. The results showed a contrast enhancement of alignment marks image compared to that of a conventional microscopy system. By using the fabrication and alignment process, process for adding waveguides to the structure is identified by using the polymer based alignment marks on the WPR 5100 layer. Mask was made by etch down process using fused silica wafer plate, Cr and AZ 3312 photoresist. At last, the developed and proposed process provides means of all-polymer based fabrication process for a flexible and parallel optical interconnect.
264

Applications of photolithographic techniques : materials modeling for double-exposure lithography and development of shape-encoded biosensor arrays

Lee, Shao-Chien 19 October 2009 (has links)
Double-exposure lithography has shown promise as potential resolu- tion enhancement technique that is attractive because it is much cheaper than double-patterning lithography and it can be deployed on existing imaging tools. However, this technology is not possible without the development of new materials with nonlinear response to exposure dose. Several materials have been proposed to implement a nonlinear response to exposure including re- versible contrast enhancement layers (rCELs), two-photon materials, interme- diate state two-photon (ISTP) materials, and optical threshold layers (OTLs). The performance of these materials in double-exposure applications was inves- tigated through computer simulation using a custom simulator. The results from the feasibility studies revealed that the ISTP and OTL types of materials showed much more promise than the rCEL and two-photon types of materi- als. Calculations show that two-photon materials will not be feasible unless achievable laser peak power in exposure tools can be signi¯cantly increased. Although rCEL materials demonstrated nonlinear behavior in double-exposure mode, only marginal image quality and process window improvements were ob- served. Using the results from the simulation work described herein, materials development work is currently ongoing to enable potential ISTP and OTL materials for manufacturing. A new biochip platform named \Mesoscale Unaddressed Functional- ized Features INdexed by Shape" (MUFFINS) was developed in the Willson Research Group at the University of Texas at Austin as a potential method to achieve a new low-cost biosensor system. The platform uses poly(ethylene glycol) hydrogels with bioprobes covalently cross-linked into the matrix for detection. Each sensor is shape-encoded with a unique pattern such that the information of the sensor is associated with the pattern and not its position. Large quantities of individual sensors can be produced separately and then self- assembled to form random arrays. Detection occurs through hybridization of the probes with °uorescently labeled targets. The key designs of the system include parallel batch fabrication using photolithography and self-assembly, in- creased information density using multiplexing, and enhanced shape-encoding with automated pattern recognition. The development of two aspects of the platform { self-assembly mechanics and pattern recognition algorithm, and a demonstration of all the key design elements using a single array are described herein. / text
265

Fast and accurate lithography simulation and optical proximity correction for nanometer design for manufacturing

Yu, Peng 23 October 2009 (has links)
As semiconductor manufacture feature sizes scale into the nanometer dimension, circuit layout printability is significantly reduced due to the fundamental limit of lithography systems. This dissertation studies related research topics in lithography simulation and optical proximity correction. A recursive integration method is used to reduce the errors in transmission cross coefficient (TCC), which is an important factor in the Hopkins Equation in aerial image simulation. The runtime is further reduced, without increasing the errors, by using the fact that TCC is usually computed on uniform grids. A flexible software framework, ELIAS, is also provided, which can be used to compute TCC for various lithography settings, such as different illuminations. Optimal coherent approximations (OCAs), which are used for full-chip image simulation, can be speeded up by considering the symmetric properties of lithography systems. The runtime improvement can be doubled without loss of accuracy. This improvement is applicable to vectorial imaging models as well. Even in the case where the symmetric properties do not hold strictly, the new method can be generalized such that it could still be faster than the old method. Besides new numerical image simulation algorithms, variations in lithography systems are also modeled. A Variational LIthography Model (VLIM) as well as its calibration method are provided. The Variational Edge Placement Error (V-EPE) metrics, which is an improvement of the original Edge Placement Error (EPE) metrics, is introduced based on the model. A true process-variation aware OPC (PV-OPC) framework is proposed using the V-EPE metric. Due to the analytical nature of VLIM, our PV-OPC is only about 2-3× slower than the conventional OPC, but it explicitly considers the two main sources of process variations (exposure dose and focus variations) during OPC. The EPE metrics have been used in conventional OPC algorithms, but it requires many intensity simulations and takes the majority of the OPC runtime. By making the OPC algorithm intensity based (IB-OPC) rather than EPE based, we can reduce the number of intensity simulations and hence reduce the OPC runtime. An efficient intensity derivative computation method is also provided, which makes the new algorithm converge faster than the EPE based algorithm. Our experimental results show a runtime speedup of more than 10× with comparable result quality compared to the EPE based OPC. The above mentioned OPC algorithms are vector based. Other categories of OPC algorithms are pixel based. Vector based algorithms in general generate less complex masks than those of pixel based ones. But pixel based algorithms produce much better results than vector based ones in terms of contour fidelity. Observing that vector based algorithms preserve mask shape topologies, which leads to lower mask complexities, we combine the strengths of both categories—the topology invariant property and the pixel based mask representation. A topological invariant pixel based OPC (TIP-OPC) algorithm is proposed, with lithography friendly mask topological invariant operations and an efficient Fast Fourier Transform (FFT) based cost function sensitivity computation. The experimental results show that TIP-OPC can achieve much better post-OPC contours compared with vector based OPC while maintaining the mask shape topologies. / text
266

SELECTIVE GROWTH OF CARBON NANOTUBES AND OXIDE NANOWIRES: APPLICATIONS IN SHADOW LITHOGRAPHY AND FABRICATION OF ALIGNED CARBON NANOTUBE MEMBRANES

Chopra, Nitin 01 January 2006 (has links)
A promising approach investigated here is to utilize thin film multilayer structures where the thickness of a catalyst layer at an exposed edge of photolithographically defined pattern determines the diameter of the nanotubes/nanowires grown from it. This can in turn be incorporated into photolithographically defined post structures resulting in an array of suspended nanowires for line-of-site shadow lithography. Success of the diameter control approach has been shown by selectively growing carbon nanotubes (CNTs) from narrow lines (12-60 nm) of SiO2, Fe, Ni, Co on micron-scale patterned substrates in a ferrocene or nonferrocene catalyzed CVD process. In addition, the concept has been extended to VS growth of CuO nanowires and VLS growth of ZnO nanowires from an exposed edge in a Al2O3/Cu(40-100 nm)/Al2O3 and Al2O3/Au(10 nm)/Al2O3 thin film multilayer structures. The exposed middle layer of patterned thin-film multilayer acts as a nm-scale wide selective growth area. The resultant CNT/nanowire diameter is directly related to the catalyst/catalyst support size. Growth kinetic studies of CuO nanowires from a thin film multilayer structure indicate diffusion controlled process. Dispersion of CNTs between lithographically defined trenches of width of 200 nm and depth of 500 nm when coupled with line-of-site deposition resulted in nm-scale line underneath the suspended CNT. The width of the resulting shadow is nearly a simple function of CNT/nanowire diameter, incident evaporation angle, and height of CNT above the substrate in a line-of-site evaporation geometry. Another promising approach to control the placement of nanotubes/nanowires is the selective functionalization of only their tips followed by selfassembly onto chemically patterned substrates. Towards this goal, arrays of aligned CNTs were impregnated with polystyrene to form aligned CNT membranes. These CNT membranes were also studied for gas and ionic transport studies. Different functionalization chemistry was performed on each side of the membrane. After dissolution of polymer matrix, a suspension of CNTs with different functionality at each tip was formed, allowing for sophisticated selfassembled architectures.
267

Nanofabrication Using Electron Beam Lithography: Novel Resist and Applications

Abbas, Arwa 12 August 2013 (has links)
This thesis addresses nanostructure fabrication techniques based on electron beam lithography, which is the most widely employed nanofabrication techniques for R&D and for the prototyping or production of photo-mask or imprint mold. The focus is on the study of novel resist and development process, as well as pattern transfer procedure after lithography. Specifically, this thesis investigates the following topics that are related to either electron beam resists, their development, or pattern transfer process after electron beam lithography: (1) The dry thermal development (contrary to conventional solvent development) of negative electron beam resists polystyrene (PS) to achieve reasonably high contrast and resolution. (2) The solvent development for polycarbonate electron beam resist, which is more desirable than the usual hot aqueous solution of NaOH developer, to achieve a low contrast that is ideal for grayscale lithography. (3) The fabrication of metal nanostructure by electron beam lithography and dry liftoff (contrary to the conventional liftoff using a strong solvent or aqueous solution), to achieved down to ~50 nm resolution. (4) The study a novel electron beam resist poly(sodium 4-styrenesulfonate) (sodium PSS) that is water soluble and water developable, to fabricate the feature size down to ~ 40 nm. And finally, (5) The fabrication of gold nanostructure on a thin membrane, which will be used as an object for novel x-ray imaging, where we developed the fabrication process for silicon nitride membrane, electroplating of gold, and pattern transfer after electron beam lithography using single layer resist and tri-layer resist stack.
268

Baudelaire et les estampes / Baudelaire and Prints

Chagniot, Claire 26 November 2010 (has links)
L'invention de la photographie bouleverse le monde de l'estampe entre 1850 et 1865. Le burin et la lithographie, pourtant récente, ne sont plus les seuls moyens de reproduire les tableaux, et l'eau-forte renaît. Dès ses premiers Salons, Baudelaire est attentif aux différents procédés. Vers 1859-1862, son action et ses articles en faveur de Charles Meryon et de la Société des aquafortistes font de lui un des principaux défenseurs de l'eau-forte originale. Après avoir acheté dans sa jeunesse des tableaux anciens, Baudelaire constitue alors une collection importante d'estampes, en rapport avec son activité de critique d'art. D'un autre côté, l'essai sur le rire, ceux sur les caricaturistes français et sur les caricaturistes étrangers, ainsi que les projets d'articles sur « L'Art philosophique » et les « Peintres de mœurs » sont entièrement ou en partie inspirés par des estampes. Ces textes donnent à Baudelaire l'occasion de poser des questions de poétique et d'esthétique, – le statut de l'artiste comique, la beauté de l'éphémère et la trivialité en art, par exemple. Comme les poèmes inspirés d'estampes, ils montrent aussi la façon dont le poète met à l'épreuve le sens des images. La dernière partie de notre travail est consacrée à l'histoire des frontispices dont Baudelaire voulut faire orner plusieurs de ses œuvres, et en particulier à celui qu'il projetait de donner à la deuxième édition des Fleurs du mal. / The invention of photography drastically changed the world of printing between 1850 and 1865. Lithography – though recent – and engraving were no longer the only means to reproduce paintings – etching came back to life. Since his first Salons, Baudelaire had been interested in these different techniques. Around 1859-1862, he became one of the key figures in the defense of original etching through his action and his articles in favour of Charles Meryon and the Société des Aquafortistes. After having bought antique paintings in his youth, Baudelaire built up a large collection of prints – in relation to his activity of art critic. Besides, his essay on laughter, the ones on French caricaturists and on foreign caricaturists, as well as his drafts of articles on “L’Art philosophique” and the “Peintres de mœurs” are entirely or partly inspired by prints. These texts gave Baudelaire the opportunity to raise issues of poetics and aesthetics, such as the position of the comic artist, the beauty of transience and triviality in art. Like his poems inspired by prints, they also show how the poet questions the meaning of images. The final part of this work is devoted to the history of frontispieces which Baudelaire wanted to use to illustrate several of his works with, and more particularly the one he planned to illustrate the second edition of Les Fleurs du mal with.
269

Comparação do uso da tirosinase purificada e na forma de extrato bruto enzimático em biossensores amperométricos para a detecção de catecol / Comparison of tyrosinase biosensors from the purified enzyme and in the crude extract form for catechol detection.

Pagliai, Rodrigo Lins 16 February 2009 (has links)
Este trabalho tem como principal objetivo comparar as respostas de biossensores amperomé-tricos preparados a partir do uso de uma enzima, a tirosinase (polifenoloxidase, PFO), quando nas formas purificada e adquirida comercialmente e de extrato bruto enzimático do fruto do abacate (Persea Americana). As soluções de PFO apresentaram valores de atividades enzimá-ticas de 479 unidades de enzimas ativas por mililitro (UA mL-1) (purificada) e 259 UA mL-1 (extrato bruto). A enzima nas duas formas (pura e como extrato bruto) foi imobilizada quimi-camente em substratos de Au modificados com monocamadas automontadas (self-assembly monolayers, SAMs) de ácido mercaptopropiônico (MPA) pela técnica de impressão por mi-crocontato (CP). Os biossensores foram preparados sobre substratos de Au modificados por CP com um molde elastomérico de polidimetilsiloxano (PDMS), cujas trilhas paralelas de 100 m foram produzidas pela cura polimérica sobre um molde mestre de GaAs. A réplica de PDMS se mostrou fiel em relação ao molde mestre nos picos e vales, mas apresentou defeitos na borda dos moldes. Com o objetivo de otimizar o funcionamento dos biossensores, eles fo-ram caracterizados pelas técnicas de voltametria cíclica e cronoamperometria com um sistema de análise de injeção em fluxo (FIA) em meio de catecol a diferentes concentrações. Os po-tenciais de oxidação do catecol nos eletrodos de Au modificados foram observados em 418 e 365 mV, em pHs ótimos de funcionamento de 7,0 e 7,2, e com limites de detecção de 6,65 nmol L-1 e 4,65 nmol L-1 para os biossensores com a enzima purificada e com o extrato bruto, respectivamente. A saturação dos sensores teve início a uma concentração de catecol de 0,02 mol L-1. Com estes resultados, mostramos que é possível o preparo de biosensores com um baixo custo, eficientes e miniaturizadas a partir do uso da PFO na forma extrato bruto do fruto do abacate para a detecção de compostos fenólicos, tal como catecol, abrindo assim a possibi-lidade de uso destes biossensores na análise e no monitoramento de pesticidas presentes no solo e na água. / The main objective of this master thesis is to compare the performance of amperometric biosensors prepared using the purified tirosinase (PPO) enzyme, (commercially acquired) and the PPO present in the enzymatic crude extract from the avocado fruit (Persea Americana). The PPO solutions had 479 units of active enzyme per milliliter (UA mL-1) (purified) and 259 UA mL-1 (crude extract). Both forms of the enzyme (purified and crude extract) were chemically immobilized on gold substrates patterned with 3-mercaptopropionic acid (MPA) self assembled monolayers (SAMs), using the microcontact printing (CP) technique. The biosensors were prepared on gold subtracts patterned using CP with a polydimethylsiloxane (PDMS) elastomeric mold, that was shaped in the form as tracks using a gallium arsenate master mold. The PDMS mold was quite similar to the master mold in its peaks and valleys, but defects were found on the edges. In order to optimize the parameters of the biosensors , they were characterized using cyclic voltammetry and chronoamperometry techniques in a FIA system by cathecol injections at different concentrations. The oxidation potentials for the cathecol analysis using the patterned biosensors were observed at 418 and 365 mV, the optimum pH were 7,0 and 7,0, with detection limits of 6,65 nmol L-1 and 4,65 nmol L-1 for the purified enzyme and crude extract biosensors, respectively. The biosensors saturation point started at 0,02 mol L-1 of cathecol concentration. With this results, we demonstrate that it is possible to use miniaturized, efficient, low cost biosensors based on tyrosine from the avocado´s fruit crude extract to detect phenolic compounds, as the cathecol. This expands the possibility of using this biosensors in the analysis and monitoring pesticides in water and soil.
270

Développement d'une technologie hybride à base de microbilles pour la détection d'anticorps IgE : vers le diagnostic d'allergies / Developement of a hybrid microbead based technology for IgE antibody detection : towards allergy diagnosis

Leonard, Anthony 27 November 2018 (has links)
Les allergies représentent un enjeu sociétal majeur dans nos sociétés modernes. Les outils de diagnostics actuels permettent la mesure de concentration d’anticorps spécifiques IgE responsables des réactions allergiques contenus dans le sérum de patient. L’intégration de nano-micro particules diminue les distances de diffusion permettant de miniaturiser les dispositifs, de diminuer le temps de réaction et d’améliorer l’efficacité du diagnostic. C’est dans cette perspective que cette thèse se positionne en développant une méthode innovante de détection des anticorps IgE par l’utilisation de microbilles polystyrènes 10µm (PS) et superparamagnétiques 1µm (SPM).L’idée explorée dans cette thèse est d’utiliser les microbilles PS comme support d’immunodosage et les propriétés magnétiques des microbilles SPM en réalisant un tri magnétique des microbilles PS. Nous avons développé cette technologie en trois étapes technologiques distinctes. Premièrement, la bio-fonctionnalisation a permis le greffage des allergènes et des anticorps à la surface des microbilles qui réagissent ensuite avec le sérum de patient. Puis, le tri magnétique a été développé pour isoler les microbilles PS en fonction de la présence ou non d’anticorps IgE à leur surface. L’efficacité de ce procédé est proportionnelle à la quantité d’IgE par microbilles. Finalement une technologie d’auto-assemblage de microbilles appelées « assemblage gravitationnel » a été développé en exploitant avantageusement les phénomènes de sédimentation et de capillarité. Il a été montré que cette technologie complémentaire à la technologie d’assemblage capillaire étend le domaine de l’assemblage à des systèmes de suspensions colloïdales denses. De plus, cette technologie permet d’atteindre une limite de détection de 2 microbilles/ml.Des tests cliniques ont été réalisés avec succès à partir de sérums de patient sensibles à l’arachide, à la noisette et à la crevette. Le temps de procédé, la limite de détection et la dynamique de détection ont été optimisés. La preuve de concept de détection des anticorps IgE a été présentée et ouvre la voie vers le diagnostic d’allergies multiplexe. / Allergies represent a major social issue for modern societies. Current diagnostic tools enables to measure the concentration of specific IgE antibodies responsible for allergic response into the patient’s serum. The use of nano-micro particles decreases diffusion distances in order to shrink the size of device, reduce the length of time reaction and improve diagnostic efficiency. In this perspective, the PhD work develop an innovative method to detect IgE antibodies by using both 10µm polystyrene (PS) and 1µm superparamagnetic (SPM) microbeads.The PhD explores the idea of using both PS microbeads as support of immunoassay and magnetic properties of SPM microbeads in order to perform a magnetic sorting of PS microbeads. We have developped this technology in 3 different technological steps. First, biofunctionnalization is used to link allergens and antibodies onto the surface of microbeads intended to react with serum patient. Then, the magnetic sorting has been developped to isolate PS microbeads depending on the presence / absence of IgE antibodies onto their surface. The efficiency of such a process is proportional to IgE quantity per microbeads. Finally, a self-assembly process of microbeads called « gravitational assembly » has been developped by studying sedimentation and capillary phenomenon. It has been shown that this complementary technology to the capillary assembly technology extend the scope of assembly to dense system of colloidal suspension. I addition, this technology reaches a detection limit of 2 microbeads per ml.Clinical trials have been succesfully performed from serum patient allergic to peanut, hazelnut or shrimp. The process time, detection limit and dynamic range of the detection system have been studied and optimized. The proof of concept of IgE antibodies detection have been presented and points the way towards the multiplex diagnosis of allergies.

Page generated in 0.0353 seconds