Дисертації з теми "Laser imprint"

La fusion par confinement inertiel (FCI) en attaque directe est une méthode envisagée pour obtenir une réaction de fusion nucléaire en irradiant une cible avec plusieurs impulsions laser de haute intensité. Cette cible est une sphère constituée d'un matériau solide appelé ablateur (généralement du polystyrène), entourant un combustible de fusion (généralement du deutérium-tritium (DT) cryogénique). L'énergie apportée par l'irradiation laser provoque l'éjection de l’ablateur et l'implosion de la cible par effet fusée. Le travail mécanique exercé sur le point chaud (le centre de la cible) pendant l'implosion doit permettre de déclencher des réactions de fusion. Actuellement, les codes hydrodynamiques radiatifs utilisés pour simuler les implosions de FCI supposent généralement que l'ablateur est initialement à l'état plasma, bien qu'il soit à l'état solide. Cet état solide pourrait jouer un rôle lors de l'interaction initiale entre les lasers et la cible. En raison de la transparence initiale de l'ablateur, le laser peut pénétrer la cible, ce qui est appelé l'effet de "shine-through", et modifier le dépôt d'énergie laser, ce qui peut conduire à une modification de la dynamique des chocs se propageant dans la cible. De plus, les modifications de l’empreinte laser peuvent influencer l’évolution des instabilités hydrodynamiques au cours de l’implosion.L’objectif de cette thèse est de développer un modèle de transition solide-plasma du polystyrène fondé sur les modèles existants et pouvant être intégré aux codes hydrodynamiques de simulation de FCI. Pour ce faire, il a fallu adapter le modèle aux contraintes spécifiques de ces codes, en tenant compte des dépendances du modèle vis-à-vis de l'évolution de toutes les grandeurs hydrodynamiques, et en optimisant les coûts numériques pour éviter une augmentation excessive du temps de simulation. L'intégration de ces modifications a requis une validation expérimentale du modèle, effectuée grâce à une expérience réalisée sur le laser GCLT du CEA-DIF mesurant l'évolution de la transmittance d'une feuille de polystyrène irradiée par une impulsion laser. Les résultats obtenus ont montré une bonne corrélation entre les simulations et les mesures expérimentales, confirmant ainsi la validité du nouveau modèle couplé. Ce modèle a ensuite été utilisé pour étudier les effets potentiels de l'état solide initial sur les simulations de FCI en attaque directe. Les résultats ont révélé que la prise en compte de la transition solide-plasma influence la croissance des instabilités hydrodynamiques. Nous avons observé une réduction des instabilités de basse fréquence spatiale pour des cibles possédant un ablateur épais, et une augmentation générale des instabilités de haute fréquence spatiale due à la non-linéarité du phénomène de transition solide-plasma
Direct drive inertial confinement fusion (ICF) is a method considered for achieving nuclear fusion reactions by irradiating a target with multiple high-intensity laser pulses. This target is a sphere made of a solid material called an ablator (usually polystyrene), which surrounds a fusion fuel (usually cryogenic deuterium-tritium (DT)). The energy delivered by the laser irradiation causes the ejection of the ablator and the implosion of the target due to the rocket effect. The mechanical work exerted on the hotspot (the center of the target) during the implosion is expected to trigger fusion reactions. Currently, the radiative hydrodynamic codes used to simulate ICF implosions generally assume that the ablator is initially in a plasma state, although it is actually in a solid state. This solid state could play a role during the initial interaction between the lasers and the target. Due to the initial transparency of the ablator, the laser can penetrate the target, leading to the "shine-through" effect, which can modify the laser energy deposition and potentially alter the dynamics of the shocks propagating within the target. Additionally, changes in the laser imprint can influence the evolution of hydrodynamic instabilities during the implosion.The objective of this thesis is to develop a solid-to-plasma transition model for polystyrene based on existing models, that can be integrated into hydrodynamic simulation codes for ICF. To achieve this, the model needed to be adapted to the specific constraints of these codes, taking into account the dependencies of the model on the evolution of all hydrodynamic quantities, and optimizing the numerical costs to avoid an excessive increase in simulation time. The integration of these modifications required experimental validation of the model, which was carried out through an experiment on the GCLT laser at CEA-DIF, measuring the evolution of the transmittance of a polystyrene sheet irradiated by a laser pulse. The results showed a good correlation between simulations and experimental measurements, confirming the validity of the new coupled model. This model was then used to study the potential effects of the initial solid state on direct drive ICF simulations. The results revealed that accounting for the solid-to-plasma transition influences the growth of hydrodynamic instabilities. Specifically, we observed a reduction in low spatial frequency instabilities for targets with a thick ablator, and a general increase in high spatial frequency instabilities due to the non-linearity of the solid-to-plasma transition phenomenon

Identification des modes de propagation a faibles pertes des guides de section circulaire et rectangulaire. Attenuation des guides de geometrie et de materiaux differents, en configuration droite et en flexion. Couplage d'un faisceau gaussien au guide et incidence des defauts de positionnement et d'orientation du guide sur la transmission. La partie experimentale decrit la fabrication du guide et le montage experimental. L'etude montre que le transport de faisceaux laser co::(2) d'une puissance avoisinant le kilowatt avec une transmission totale de 99% est possible au moyen d'un guide creux rectangulaire metallique

Ce mémoire est consacré à l'étude d'empilements multicouches de semi-conducteurs gaas/algaas, et plus particulièrement d'empilements périodiques (réflecteurs de Bragg), étudiés en tant que tels ou comme éléments intégrés à des structures plus complexes. Les structures étudiées sont caractérisées par leur spectre de réflectivité linéaire. Pour interpréter ces résultats, nous développons deux approches théoriques complémentaires: la première, basée sur un formalisme matriciel, permet de décrire exactement la propagation d'une onde optique dans une structure stratifiée quelconque et a servi de support a un programme de calcul. La seconde, en termes de couplage d'ondes, complète utilement la première en fournissant les dépendances explicites du comportement des structures en fonction des indices et des épaisseurs des matériaux choisis. Nous établissons l'expression explicite de la constante de couplage et nous exposons les principes de la synthèse des dispositifs complexes. Nous consacrons tout un chapitre aux microcavités lasers à émission surfacique. Dans un échantillon réalisé par le l.c.r. de Thomson-csf, nous avons validé la possibilité d'une émission laser biraie. Ce composant a été utilisé pour réinjecter une cavité laser saphir dopé au titane. Nous avons par ailleurs pompé la micro cavité par des impulsions optiques ultrabrèves (=100 FS) et analysé son spectre d'émission laser biraie avec une camera à balayage de fente. A l'aide d'un modèle simple, nous montrons qu'il est nécessaire de tenir compte non seulement des porteurs libres photo créés dans les puits quantiques, mais encore de ceux crées dans les barrières, suite à l'absorption par ces dernières d'une partie du flux de pompé. La prise en compte de cet effet dans nos simulations donne des résultats en bon accord avec nos observations expérimentales

La stéréolithographie biphotonique (TPS) est une technique de microfabrication 3D basée sur la polymérisation par absorption biphotonique qui permet d’obtenir en une seule étape des structures 3D complexes avec des détails sub-100nm. Aujourd’hui, en raison des conditions spécifiques de fabrication liées à la TPS (fort flux, confinement spatial de la photoréaction,…), un des enjeux concerne le développement de matériaux fonctionnels compatibles avec ce procédé. Dans ce contexte, l’objectif de cette thèse a été de développer de nouveaux matériaux fonctionnels à base de polymères à empreintes moléculaires (MIP) pour élaborer des capteurs chimiques. Une première partie de ce travail a consisté à mettre en place différentes méthodes dédiées à la caractérisation des propriétés géométriques, chimiques et mécaniques des matériaux élaborés par TPS. Par exemple, la vibrométrie laser a été utilisée pour la première fois afin de sonder de façon non-invasive les propriétés mécaniques de microstructures réalisées par TPS. Dans un second temps, ce travail a été mis à profit pour étudier l’impact du processus de fabrication (i.e. conditions photoniques) ainsi que des paramètres physico-chimiques affectant la photoréaction (i.e. inhibition par oxygène et nature du monomère) sur les propriétés finales des matériaux. Enfin, en s’appuyant sur les résultats obtenus, des microcapteurs chimiques à base de MIP, à lecture optique ou mécanique, ont été fabriqués. Leurs propriétés de reconnaissance moléculaire, ainsi que leurs sélectivités ont été démontrées pour une molécule cible modèle (D-L-Phe)
The two-photon stereolithography (TPS) technique is a micro-nanofabrication method based on photopolymerization by two-photon absorption that allows in a single manufacturing step to obtain complex 3D structures with high-resolution details (sub-100nm). Due to the specific conditions of TPS process (intense photon flux, spatial confinement of the photoreaction…) one of the main concerns today is the development of functional materials compatible with the TPS. According to the aforementioned, the general objective of this thesis was to develop new functional materials based on molecularly imprinted polymers (MIP) to elaborate chemical microsensors. In the first step of this work, different methods were implemented to characterize the geometrical, chemical and mechanical properties of the materials synthesized by TPS. For example, laser-Doppler vibrometry was used for first time to evaluate the mechanical properties of microstructures fabricated by TPS in a non-invasive way. In the second step, the characterization methodology was used to study the impact of the manufacturing process (i.e. photonic conditions) and the physicochemical parameters that affect the photoreaction (i.e. oxygen inhibition and the nature of the monomer) and the final properties of the materials. Finally, the obtained results enabled the prototyping of chemical microsensors based on MIP. Their molecular recognition properties and their selectivity were demonstrated for the molecule (D-L-Phe) by an optical and a mechanical sensing method

Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.
Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.

碩士
國立成功大學
機械工程學系碩博士班
92
The object of this thesis is to study the imprint phenomena of nano-scale nickel substrate using molecular dynamics theory, and the results are explained and compared with actual experiments. The imprint workpiece in the numerical simulation is the material of nickel of the construction of FCC. The Gear’s fifth order predictor-corrector algorithms is adapted to calculate the positions, velocities, and accelerations of atoms under various displacement condition, while the interactions of atoms are dealt with Verlet’s neighbor lists and Morse’s potential. 　　The numerical simulations contain three parts. The first part is to study the difference of force on the compressing molds with various system temperatures. The imprint substrate is made of nickel and the mold is copper. The second part is to study the stress on the imprint substrates with various system temperatures. And the third part is to study the spring-back of substrate atoms under different temperature after imprint. From the numerical simulations, it can be found: (1) the mold will bring substrate atoms away from the workpiece, (2) the loading force is lower while system temperature is higher at the imprint process (3) the high compressing stress can be found at the bottom of the mold and in the corner of imprint area, (4) the spring-back phenomenon was obtained while the deformation and temperature are increased.

The important roles of fluid dynamics in immersion lithography (IL) and step-and-flash imprint lithography (S FIL) are analyzed experimentally and theoretically. In IL there are many challenges with managing a fluid droplet between the lens and the wafer, including preventing separation of the fluid droplet from the lens and deposition of small droplets behind the lens. Fluid management is also critical in S FIL because the imprint fluid creates capillary and lubrication forces, both of which are primarily responsible for the dynamics of the template and fluid motion. The fluid flow and shape of the wafer determine how uniform the gap height between the wafer and the template is, and they affect the resistance during the alignment phase. IL was investigated as a methodology to improve laser lithography for making photomasks. The fluid flow in IL was investigated by building a test apparatus to simulate the motion of the fluid droplet during microlithographic production, and using this apparatus to conduct experiments on various immersion fluids and wafer topcoats to determine what instabilities would occur. A theoretical model was used to predict the fluid separation instabilities. Finite element simulations were also used to model the fluid droplet, and these simulations accurately predict the fluid instabilities and quantitatively agreed with the model and experiments. It is shown that the process is viable: capillary forces are sufficient to keep the fluid droplet stable, heating effects due to the laser are negligible, and other concerns such as evaporation and dissolution are manageable. Euler beam theory and the lubrication equation were used to model the bending of an S FIL template and the flow of the fluid between the template and a non-flat wafer. The template filling time, conformance of the template to the wafer, and the alignment phase are investigated with an analytical model and finite element simulations. Analysis and simulations show that uniformity of the residual film thickness and ease of proper alignment depend greatly on the planarity of the wafer, the properties of the template, and the surface tension of the fluid.
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碩士
國立清華大學
動力機械工程學系
96
In order to improve the utilization ratio of light source in LCD display, we propose to replace the traditional absorption polarizer with the reflection nano-polarizer, and combine with nanoimprint lithography technology to achieve the goal of mass production of nano-polarizer. Accordingly, the nanoimprint mold plays a critical role in nanoimprint process. There are many different methods to fabricate the nanoimprint mold, for example, optical lithography, E-beam lithography and so on. Amount these techniques, laser interference lithography provides an inexpensive, rapid and easy way to fabricate nano-patterns. To fabricate high density and large-area nano-patterns, some ameliorated interference lithography systems have been proposed. However, these interference lithography systems are either complicated or expensive. The objective of this study is aimed at designing a compact and cost-effective interference lithography system and by step-and-tiling method to fabricate large-area nanoimprint mold. Interference lithography is based on the interference of two or more coherent laser beams incident from different directions intersect on a photoresist-coated substrate. The resulting fringes recorded in the photoresist can be used to fabricate 1-D or 2-D period structures. In this study, we first consider the standing wave effect in interference lithography. By establishing a Hardmask design model and combine with the use of ARC, we can reduce the standing wave effect more effectively. The experimental set-up used in this work is Lloyds-mirror . To combine with the two-axis nano-stage and maintain the stability and precision of nano-stage, we designed a horizental-type Lloyd’s-mirror set-up and verified the viability. Besides, to better understand the factors that contribute to the fabrication of nanoimprint mold, we also consider the experiment process recipe, the mask material suit for this set-up, and the optimum condition for tiling. Similarly, a two-dimensional pattern can be generated by superposition of two sinusoidal standing waves with this sep-up. In the consideration of cost-effective condition, the compact interference lithography system not only provides a rapid way to fabricate large-area nanoimprint mold but has the advantage of flexibility in fabricating different dimensional period structures.

碩士
國立中正大學
機械工程所
95
The polymer thin film layer is mainly used in nano imprint process. It is uncommonly applied imprint process to metal thin film due to it needs ultra-high stamp pressure and spring back problems. How to choose working temperature and metal layer structures to reduce the imprint force is the major research topics nowadays. The research works presented in this thesis uses the finite element method to simu-late nano imprint process on Aluminum thin film. The numerical mesh quality problems due to large deformation are improved by adaptive meshing technique. The temperature dependent strain-stress curves of Aluminum wire were given from micro-force tensile test, and modi-fied by compared with real imprint experimental results. Referring to the literature produced metal/polymer bi-layer structures (NIMB) ex-periment; we modified the single metal layer simulation model to bi-layer Aluminum/polymer thin film. Various thickness ratios and form-ing temperatures are studied by bi-layer simulation model to reveal how they affected the imprint force. The results presented in this study could great help to choose better bi-layer structure as well as the imprint parameters.

Recently, laser scribed graphene (LSG) technology has shown great potential for the development of a plethora of sensing platforms due to its high sensitivity, 3D porous structure, and flexibility. Molecularly imprinted polymers (MIPs) have shown high potential as recognition elements for many applications such as biosensing. Hence, we report in this thesis a novel biosensing platform that utilizes nanostructured gold to enhance the performance of LSG sensors coupled with a biomimetic MIP biosensor. To the best of our knowledge, this is the first report of a nanostructured gold modified MIP based LSG biosensor to detect HER-2, which is an important breast cancer biomarker. HER-2 positive breast cancer is more aggressive and does not respond to the same treatment as standard breast cancer. As such, a simple and accurate sensing approach is highly needed for early detection of this type of cancer biomarkers. The LSG sensor platform was fabricated by irradiation of polyimide substrates using a CO2 laser under optimized conditions. Nanostructured gold was electrodeposited onto LSG to enhance its sensitivity and active surface area. Deposition parameters such as deposition voltage, deposition time, and gold chloride (HAuCl4) concentration were optimized to yield complete nanostructured gold coverage and enhanced electrical conductivity of LSG-Au electrodes. A deposition voltage of -0.9 V at 50 mM HAuCl4 for 4 minutes proved to be the optimal condition for gold deposition to yield a 150% peak current enhancement. To fabricate our MIP biosensor, 3,4- ethylenedioxythiophene (EDOT) was chosen from several functional monomers to form PEDOT due to its high conductivity and synergy with nanostructured gold. Electropolymerization of EDOT is performed after adsorbing 0.4mg/mL of HER-2 on the LSG-Au electrode for 20 min. The efficiency of LSG-Au-MIP was optimized by choosing an appropriate extraction agent and HER-2 concentration to be adsorbed on gold. The developed sensing strategy could differentiate between three rebinding concentrations of 10 ng/mL, 100ng/mL, and 200 ng/mL, which is sufficient to determine the HER-2 status of breast cancer since the clinical cut-off is 30.5ng/mL. The developed sensing strategy showed a high degree of novelty and could be useful for the non-invasive detection of cancer biomarkers.

博士
國立清華大學
動力機械工程學系
100
When the dimension of the microelectronic structure decreases, high manufacturing cost is inevitable. A low-cost manufacturing technique for nanostructures is desired. Nano-imprint lithography (NIL) has the potential to meet the expectations. Nano-imprint lithography patterns the resist with physical deformation using a mold at nano-scale. However, the variation of environmental conditions and process parameters seriously affect the reproduction quality. To ensure the quality of the imprinted pattern is essential for industry. In this study, the author applies the surface plasmon resonance (SPR) to develop a functional imprinting mold, which has non-destructive measurement capability for the quality of the imprinted pattern. During measuring process, the excited surface plasmon can penetrate into the interface between mold surface and imprinted material. If there is filling defects in the interface, the SPR behavior will be affected, including the reflectivity spectrum change and resonance angle shift. If the penetration of surface plasmon can reach the substrate, the thickness of residual layer also affects the SPR behavior. Based on the reflectivity spectrum curve and resonance angle, the quality of the imprinted pattern can be told. According to the simulation and experimental results, the developed system can detect the filling defects as low as 1.7 % of the volume of the mold cavity and 8 nm residual layer thickness. This new application of SPR promises to improve NIL performance in the nanofabrication industry.

碩士
國立中央大學
光電科學與工程學系
102
In recent years, the efficiency of organic photovoltaic has increasing dramatically through numerous researchers’ contribution. From single layer organic photovoltaic to tandem organic photovoltaic, both the absorbance of photon and charge collection is increasing gradually. We are looking forward to producing commercial batteries. This thesis focuses on enhancement of electron collection efficiency and photon absorbance in organic photovoltaic through thermal imprint lithography on active layer. The enhancement of photon absorbance is proved with spectrophotometer in this photovoltaic, and collaborated with the FDTD simulation. Finally, we perform optical simulation on varying the structure period from micrometer to nanometer scale. The photocurrent of device is measured under standard AM 1.5G solar spectrum for analyzing electrical property by I-V curve. Basing on the same imprint pressure, the short circuit current of depth of 10 nm grating active layer in OPV is 0.05 mA（relative improvement 6.6%） higher than planar one. The same phenomena can be found under higher imprinted pressure that the short circuit current of depth of 30 nm grating active layer in OPV is 0.118 mA （relative improvement 20%）higher than planar one. Therefore, the contribution of anti-reflection caused from imprinted micro-grating structure in OPV can enhance photocurrent more than planar one.

The Bio J-FIL process has been demonstrated to be a viable method for manufacturing nanoscale, polymeric drug carriers. The process allows for precise control of the size and shape of the drug carriers. While the original process is sufficient for research scale projects, reliability issues have prevented it from being scalable to levels that could potentially be used for mass-production of the drug carriers. In this thesis, a detailed root cause analysis has been conducted to determine the cause of the reliability issues limiting the Bio JFIL process. A series of experiments with varying substrate and imprint fluid combinations were conducted to pinpoint the cause of imprint failure in the Bio J-FIL process. Upon determining the cause of failure, an alternative imprint process was investigated that sought to increase the variety of materials used in the process by utilizing an intermediary layer. This process is referred to in this thesis as the Bio JFIL-I process. The results using Bio JFIL-I indicated increased reliability over the standard Bio J-FIL process. Further refinement of the Bio JFIL-I process could also address additional issues with the Bio J-FIL process unrelated to process reliability. The Bio JFIL-I approach presented in this thesis is complementary to other approaches that have been recently pursued in the literature which are discussed in the thesis.
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