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Matz, John E. (John Edward) 1968. "Carbide formation in a nickel-based superalloy during electron beam solid freeform fabrication." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9540.
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Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999.Vita.
Includes bibliographical references (leaves 90-93).
The Electron Beam Solid Freeform Fabrication process involves the use of an electron beam to make near-net-shape metal parts without the need for tooling. Material in wire form is fed into a melt pool maintained on the surface of the part by the electron beam and a positioning system causes the deposition to occur in a line-by-line, layer-by-layer fashion. Solidification occurs at a high rate, forming a fine dendritic microstructure and fine dispersion of primary carbides. This structure is believed to be optimal for the manufacture and safe use of certain nickel-base superalloy parts, notably turbine disks. The growth of carbide particles from the liquid during EBSFF processing of Alloy 718 has been modeled assuming diffusion control and isolated spherical carbides. The driving force for growth is assumed to increase in a linear manner throughout the temperature range of carbide precipitation. The model predicts the maximum carbide size as a function of EBSFF operating parameters and the alloy niobium and carbon levels. For the material and conditions used experimentally in this work, the model predicts a maximum diameter of approximately I .0 [mu]m. The maximum carbide size will become an important determining factor for turbine disk performance when oxide and nitride inclusions have been eliminated through improved melt practices. To illustrate this, the low-cycle fatigue life as a function of carbide size for a standard specimen geometry was calculated. Extraction replica transmission electron microscopy of EBSFF samples identified carbides in the 300-600 nm range, consistent with a population having the predicted maximum size. Another dispersion of carbides larger than 3 [mu]m was also observed in the EBSFF samples. These are believed to be original carbides that survived the EBSFF thermal cycle without completely dissolving. More thorough dissolution can probably be obtained with EBSFF process modifications. Control material from a conventional vacuum arc remelted ingot with similar composition was also examined and plate-like carbides up to 40 [mu]m in length were noted. This is an indication of the enormous potential of the EBSFF process to refine the carbide morphology and size distribution without the need for a reduction in carbon content.
by John Edward Matz.
Sc.D.
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Nelson, Erik Walter. "Combined Compression and Shear Structural Evaluation of Stiffened Panels Fabricated Using Electron Beam Freeform Fabrication." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/43583.
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Unitized aircraft structures have the potential to be more efficient than current aircraft structures. The Electron Beam Freeform Fabrication (EBF3) process can be used to manufacture unitized aircraft structures. The structural efficiency of blade stiffened panels made with EBF3 was compared to panels made by integrally machining from thick plate. The panels were tested under two load cases in a combined compression-shear load test fixture. One load case tested the panels' responses to a higher compressive load than the shear load. The second load case tested the panels' responses to an equal compressive and shear load. Finite element analysis was performed to compare with the experimental results. The EBF3 panels failed at a 18.5% lower buckling load than the machined panels when loaded mostly in compression but at an almost two times higher buckling load than the machined panels when the shear matched the compressive load. The finite element analysis was in good agreement with the experimental results prior to buckling. The results demonstrate that the EBF3 process has the capabilities of manufacturing stiffened panels that behave similarly to machined panels prior to buckling. Once the EBF3 panels buckled, the buckled shape of the EBF3 panels was different from the machined panels, generally buckling in the opposite direction of what was observed with the machined panels. This was also expected based on the finite element analysis. The different post-buckling response between the two manufacturing techniques was attributed to the residual stress and associated distortion induced during the EBF3 manufacturing process.Master of Science
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Waters, Brent R. "Mechanical Properties of Inconel 718 Processed Using Electron Beam Free Form Fabrication (EBF3)." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6717.
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Electron beam freeform fabrication (EBF3) is a rapid metal deposition process that works efficiently with the wieldable alloy Inconel 718 (IN 718). EBF3 is a developing additive manufacturing (AM) process that can manufacture IN 718 parts directly from computer aided design (CAD) data. EBF3 can produce parts significantly faster and more energy efficient than competing IN 718 AM technologies. The EBF3 process utilizes metal wire feedstock which is induced into a molten pool using a focused electron beam in a vacuum environment. This allows parts to be built layer by layer, creating intricate shapes that can be produced cheaper and faster than traditionally manufactured IN 718 parts. Furthermore, it allows traditionally manufactured parts to be modified as additional form is added to them using EBF3. Multiple industries rely on IN 718 parts and can utilize this technology including aerospace engineering, oil refinery, nuclear power generation, and food processing.A main drawback of EBF3 is the lack of knowledge of the effect different EBF3 build techniques will have on the properties of the deposited materials. Most of the reliable data on the mechanical properties relate to a linear build-up strategy and focus on the mechanical properties in the deposition direction (DD). There is no data related to other build-up techniques such as rotation build-up or transitional builds from forged material to EBF3 material. Reliable data on the behavior and microstructure of EBF3 material in a direction other than the DD is also difficult to find. Previous studies showed build-up height influenced mechanical properties but its role is not fully understood yet. This paper presents the mechanical properties and microstructure of an IN 718 plate built using a EBF3 rotational build-up strategy through utilizing a forged plug in the center. The tensile properties of samples at the transition from forged to EBF3 material showed higher ductility and reduced strength than pure EBF3 material. This is likely due the influence of the forge material in one half of the specimen. Samples taken at approximately 15 degree increments from 0 to 90 degrees rotation to the DD in the additive portion of the plate were subjected to tensile testing. Along the build height, or the transverse direction (TD), the lowest strength was demonstrated and the TD aligned strongly to a <001> texture. Samples 45 degrees to the DD showed the greatest strength due to their preference for aligning to a <111> texture. Samples low on the build height demonstrated a higher strength than those on the top and displayed grain structures along the TD which were long, linear, and narrow across multiple deposition layers.
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Gaytan, Guillen Sara Marisela. "Additive layer manufacturing of TI-6AL-4V by electron beam melting from powder particles solid, mesh and foam components study /." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Kottman, Michael Andrew. "Additive Manufacturing of Maraging 250 Steels for the Rejuvenation and Repurposing of Die Casting Tooling." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1416854466.
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Davé, Vivek Ramesh. "Electron beam (EB)-assisted materials fabrication." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11505.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1995.Vita.
Includes bibliographical references (v. 2, leaves 277-279).
by Vivek Ramesh Davé.
Ph.D.
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Onyeako, Isidore. "Resolution-aware Slicing of CAD Data for 3D Printing." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34303.
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3D printing applications have achieved increased success as an additive manufacturing (AM) process. Micro-structure of mechanical/biological materials present design challenges owing to the resolution of 3D printers and material properties/composition. Biological materials are complex in structure and composition. Efforts have been made by 3D printer manufacturers to provide materials with varying physical, mechanical and chemical properties, to handle simple to complex applications. As 3D printing is finding more medical applications, we expect future uses in areas such as hip replacement - where smoothness of the femoral head is important to reduce friction that can cause a lot of pain to a patient. The issue of print resolution plays a vital role due to staircase effect. In some practical applications where 3D printing is intended to produce replacement parts with joints with movable parts, low resolution printing results in fused joints when the joint clearance is intended to be very small. Various 3D printers are capable of print resolutions of up to 600dpi (dots per inch) as quoted in their datasheets. Although the above quoted level of detail can satisfy the micro-structure needs of a large set of biological/mechanical models under investigation, it is important to include the ability of a 3D slicing application to check that the printer can properly produce the feature with the smallest detail in a model. A way to perform this check would be the physical measurement of printed parts and comparison to expected results. Our work includes a method for using ray casting to detect features in the 3D CAD models whose sizes are below the minimum allowed by the printer resolution. The resolution validation method is tested using a few simple and complex 3D models. Our proposed method serves two purposes: (a) to assist CAD model designers in developing models whose printability is assured. This is achieved by warning or preventing the designer when they are about to perform shape operations that will lead to regions/features with sizes lower than that of the printer resolution; (b) to validate slicing outputs before generation of G-Codes to identify regions/features with sizes lower than the printer resolution.
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Leonard, S. "Negative polymeric resists for electron beam lithography." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234905.
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Ervin, Jennifer Kelly. "Post Heat Treatment Effects of Ti-6Al-4V Produced via Solid Freeform Electron Beam Melting." NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-05012008-105845/.
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Traditionally, Ti-6Al-4V components are fabricated by forging or casting. However, these methods of production require expensive dies or molds. The cost per part is very high for those parts produced in low quantities. The solid freeform electron beam melting process aims to produce high dimensional tolerance parts with similar mechanical properties at a lower cost by melting Ti-6Al-4V powder in a layer by layer fashion using high energy electrons. Due to the directional solidification effects, the microstructure seen in this process consists of a columnar grain structure along the growth direction and an equiaxed structure at the cross-sectional growth plane. This type of structure is thought to contribute to the anisotropy of tensile properties discovered in previous research. Although, preferred orientation of the α laths may play a role as well. Heat treatments above the β transus are performed in order to improve the tensile properties, specifically ductility, with intensions to remove preferred orientation and to disunite the columnar grain structure. Tensile testing, fractography, optical microscopy, and x-ray diffraction are used to characterize and compare the as-processed and β heat treated electron beam melted specimens. It is found for all β treated conditions, the ductility increases compared to the as-processed specimens, although the strength decreases. The mode of fracture changes from ductile dimple rupture in the asprocessed condition to transgranular cleavage with ductile dimple rupture for the heat treated specimens. The macrostructure and microstructure in the as-processed and heat treated specimens contrasted greatly. The macrostructure changes from a fully columnar structure to a mixture of columnar and equiaxed grains. A fine acicular microstructure is observed in the as-processed samples, whereas a broad lamellar colony microstructure is formed during heat treatment. The presence of a colony microstructure is a possible reason for the improvement in ductility. From the x-ray data obtained, the preferred orientation is not reduced but instead increases after heat treating in the β region which likely is a result of the favorable rearrangement of slip systems due to the change in α lath orientation.
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Taslimi, Shahrzad. "Fabrication of diffractive optical elements by electron beam lithography." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=96963.
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Diffractive optical elements (DOEs) are an important component in the success of optical Microsystems. Electron beam lithography is a key part of fabricating these elements with submicron feature dimensions. This thesis presents work done on the development of a process for the fabrication of multilevel diffractive optics in glass substrates using this method. This project investigates various challenges involved in the process, addresses possible problems that may arise and proposes and investigates solutions to resolve them. Sources of possible error in the creation and transfer of the patterns are identified and methods of eliminating or minimizing these errors are presented. Some of the main sources of error arise from charging due to electron accumulation and alignment issues during electron beam lithography.Éléments d'optiques diffractives (EODs) composent une partie essentielle dans le succès de microsystèmes optiques. Lithographie à faisceau d'électrons est un élément clé pour la fabrication des structures avec des dimensions critiques submicroniques. Cette thèse présente le travail fait sur le développement d'un processus pour la fabrication des optiques diffractives en utilisant cette méthode. Ce projet étudie des divers défis impliqués dans ce processus, traite des problèmes qui pourrait surgir et propose des solutions pour les résoudre. Les sources d'erreur possible dans la création et le transfert des modèles sont identifiées et des méthodes de les éliminer ou les minimiser sont présentées. Certaines des erreurs sont attribuées à l'accumulation d'électrons et aux problèmes d'alignement lors de la lithographie.
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Bedson, Thomas Robert. "Nanostructure fabrication using electron beam irradiation of organometallic compounds." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369333.
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Pauza, Andrew John. "The fabrication of Josephson junctions with an electron beam." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320032.
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Binnie, C. E. "The fabrication of small geometry MOSFET's using electron beam lithography." Thesis, University of Glasgow, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372399.
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Chen, Giin-Shan. "Mechanisms of direct electron beam nanolithography and nanostructure fabrication methods." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321028.
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Kong, David Sun 1979. "Nanostructure fabrication by electron and ion beam patterning of nanoparticles." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28346.
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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2004.Includes bibliographical references (leaves 82-83).
Two modes of energetic beam-mediated fabrication have been investigated, namely focused ion beam (FIB) direct-writing of nanoparticles, and a technique for electrostatically patterning ionized inorganic nanoparticles, termed nanoxerography. A FIB has been used to directly pattern thin films of organometallic Ag-precursors down to a resolution of 100 nm. The sensitivity of the resist to 30 keV Ga+ ions was measured to be approximately 5 C/cm2. Using this technique arbitrary structures were fabricated in two and three dimensions with resistivity on the order of 1x10 4 Q-cm and 1x1 0-5 Q-cm for single- and multi-layer structures, respectively. A new unit of merit for characterizing direct-write processes, termed resistivity-dose (Q-jC/cm), has been introduced. A Nanocluster Source capable of generating a beam of charged, inorganic nanoparticles has been characterized. The relationship between power supplied to the magnetron of the source and the size of deposited clusters has been plotted. Techniques for utilizing such clusters to develop latent electrified images patterned by an electron beam (EB) have been proposed. The charge-storing characteristics of a variety of substrates such as mylar and polyimide were studied by developing EB-patterned charge images with toner particles.
David Sun Kong.
S.M.
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Travis, David William. "High resolution electron beam lithography for exploratory silicon device fabrication." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/14571.
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This thesis reports on a study into the fabrication of metal oxide silicon field effect transistors using electron beam lithography to pattern features with dimensions down to 100nm and below. The study is in an area of extensive research, with devices at these dimensions of interest for future generations of integrated circuit manufacture. The design and construction of a high resolution electron beam system is reported. The system is based on a very high resolution scanning electron microscope equipped with a thermal field emission gun. Chemically amplified resist processes, for electron beam lithography, have been characterised for silicon device fabrication and sub 100nm patterns have been demonstrated. The development of a fabrication process for silicon devices, with dimensions down to 100nm, is described. The process uses electron beam lithography for all levels of patterning and electrical measurements are reported for a range of the fabricated devices. Devices fabricated in this study are used to explore a novel width modification technique using focused ion beam milling to reduce the current drive of individual transistors. The transistors are characterised before and after modification and electrical measurements are presented which provide the basis for a new chip modification strategy.
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Yang, Yugu. "Feedback Control for Electron Beam Lithography." UKnowledge, 2012. http://uknowledge.uky.edu/ece_etds/9.
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Scanning-electron-beam lithography (SEBL) is the primary technology to generate arbitrary features at the nano-scale. However, pattern placement accuracy still remains poor compared to its resolution due to the open-loop nature of SEBL systems. Vibration, stray electromagnetic fields, deflection distortion and hysteresis, substrate charging, and other factors prevent the electron-beam from reaching its target position and one has no way to determine the actual beam position during patterning with conventional systems. To improve the pattern placement accuracy, spatial-phase-locked electron-beam lithography (SPLEBL) provides feedback control of electron-beam position by monitoring the secondary electron signal from electron-transparent fiducial grids on the substrate. While scanning the electron beam over the fiducial grids, the phase of the grid signal is analyzed to estimate the electron-beam position error; then the estimates are sent back to beam deflection system to correct the position error. In this way, closed-loop control is provided to ensure pattern placement accuracy. The implementation of spatial-phase-locking on high speed field-programmable gate array (FPGA) provides a low-cost method to create a nano-manufacturing platform with 1 nm precision and significantly improved throughput.
Shot-to-shot, or pixel-to-pixel, dose variation during EBL is a significant practical and fundamental problem. Dose variations associated with charging, electron source instability, optical system drift, and ultimately shot noise in the beam itself conspire to increase critical dimension variability and line width roughness and to limit the throughput. It would be an important improvement to e-beam patterning technology if real-time feedback control of electron-dose were provided to improve pattern quality and throughput even beyond the shot noise limit. A novel approach is proposed in this document to achieve the real-time dose control based on the measurement of electron arrival at the sample to be patterned, rather than from the source or another point in the electron-optical system. A dose control algorithm, implementation on FPGA, and initial experiment results for the real-time feedback dose control on the e-beam patterning tool is also presented.
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Brown, Karl. "Coupled electron gases fabricated by in situ ion beam lithography and MBE growth." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319460.
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Gonzalez, Martinez Ignacio Guillermo. "Novel thermal and electron-beam approaches for the fabrication of boron-rich nanowires." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-218019.
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Pursuing the development and implementation of novel synthesis techniques to produce nanostructures with an interesting set of properties is a goal that advances the frontiers of nanotechnology. Also of fundamental importance is to revisit well-established synthesis techniques employing a new set of materials as precursors, substrates and catalysts. Fundamental breakthroughs in the field of nanotechnology can be achieved by developing new synthesis procedures as well as by adapting known procedures to new materials. This thesis focuses on both kinds of experiments.
A variant of chemical vapor deposition (CVD) has been used to produce Al5BO9 nanowires out of sapphire wafers without the need of a catalyst material. The novelty of the work relies on the formation mechanism of the Al5BO9 nanowires. Essentially, the process can be described as a large-scale topological transformation taking place on the substrate’s surface as its chemical composition changes due to the arrival of precursor molecules. Dense mats of Al5BO9 nanowires cover large areas of the substrate that were previously relatively flat. The process is enhanced by a high temperature and the presence of pre-existing superficial defects (cracks, terraces, etc.) on the substrates. Al5BO9 nanowires as well as B/BOX nanowires and BOX nanotubes were also produced via a novel in-situ electron beam-induced synthesis technique. The process was carried out at room temperature and inside a transmission electron microscope. Au nanoparticles were used as catalyst for the case of B/BOX nanowires and BOX nanotubes, while the Al5BO9 nanowires were synthesized without the need of a catalyst material. The formation and growth of the nanostructures is solely driven by the electron beam. The growth mechanism of the B/BOX nanowires and BOX nanotubes relies on interplay between electrostatic charging of the precursor material (to produce and transport feedstock material) and electron stimulated desorption of oxygen which is able to activate the catalytic properties of the Au nanoparticles. For the case Al5BO9 nanowires a nucleation process based on massive atomic rearrangement in the precursor is instigated by the e-beam, afterwards, the length of some of the nanowires can be extended by a mechanism analogous to that of the growth of the B/BOX nanowires.
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Piaget, Alexandre. "Maîtrise de la qualité en fabrication additive." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI004/document.
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En utilisant des solutions de production issues des technologies de Fabrication Additive (FA), l’industrie s’ouvre de nouvelles possibilités pour la fabrication de pièces à haute valeur ajoutée. Dans le but d’être pleinement exploitables, ces procédés de fabrication doivent permettre la réalisation de pièces dont la qualité est adaptée aux besoins de l’industrie. Ces travaux se concentrent sur deux points ciblés de la maîtrise de la qualité en FA appliquée à la technologie Electron Beam Melting (EBM).Le premier point abordé s’intéresse à l’impact de la position d’une pièce dans l’espace de fabrication d’une machine sur la qualité géométrique de cette pièce. Pour caractériser l’espace de fabrication de la machine Arcam A1, plusieurs séries de pièces sont fabriquées à différentes localisation de l’espace, puis comparées à leur design initial. Les écarts mesurés entre les pièces et leur géométrie souhaitée montrent que la périphérie de l’espace de fabrication est une zone sujette à d’importants défauts géométriques. Ces défauts sont caractérisés et des solutions sont proposées pour en limiter l’impact sur la qualité géométrie des pièces.Le second point traite de la porosité des pièces fabriquées. Lorsque l’apport énergétique du faisceau d’électron n’est pas adéquat pour fondre correctement la poudre, des pores peuvent se former dans le matériau des pièces fabriquées. La géométrie et le matériau des pièces rendent difficiles la détection de ses pores. Une méthode de détection est proposée pour détecter la présence de pores dans une pièce via un contrôle standardisé sur un élément qui copie les conditions de fusion de la pièce. Cette méthode propose deux alternatives de contrôle : un contrôle optique (rapide, abordable mais peu précis) et un contrôle tomographique (plus précis que le précédent mais moins rapide et abordable). Un algorithme de traitement d’image innovant a été développé dans le cadre de cette étude afin de rendre les tomographies du témoin plus fiablesBy using production solutions from Additive Manufacturing (AM) technologies, the industry is opening up new possibilities for manufacturing high added value parts. In order to be fully exploitable, these manufacturing processes must allow the production of parts whose quality is adapted to the needs of the industry. This work focuses on two aiming points of quality control in AM applied to Electron Beam Melting (EBM) technology.The first point deals with the impact of a part position in the manufacturing space of a machine on the geometric quality of this part. To characterize the manufacturing space of the Arcam A1 machine, several series of parts are manufactured at different locations of the space, then compared to their initial design. The differences measured between the parts and their desired geometry show that the periphery of the manufacturing space is a zone subject to important geometrical defects. These defects are characterized and solutions are proposed to limit the impact on the geometrical quality of parts.The second point deals with the porosity of manufactured parts. When the energy supply of the electron beam is not adequate to melt the powder properly, pores can form in the material of the manufactured parts. The geometry and material of the parts make it difficult to detect its pores. A detection method is provided to detect the presence of pores in parts via a standardized control on an item that copies the parts merging conditions. This method offers two control alternatives: an optical control (fast, affordable but not very accurate) and a tomographic control (more accurate than the previous one but slower and costlier). An innovative image processing algorithm is developed as part of this study to make the item tomography scans more reliable
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Stay, Justin L. "Multi-beam-interference-based methodology for the fabrication of photonic crystal structures." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31783.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.Committee Chair: Thomas K. Gaylord; Committee Member: Donald D. Davis; Committee Member: Gee-Kung Chang; Committee Member: Muhannad S. Bakir; Committee Member: Phillip N. First. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Lutwyche, Mark Ian. "The use of electron beam lithography and chemical etching for the fabrication of micromechanical structures." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239063.
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Sultan, Mansoor A. "ELECTRON-BEAM PATTERNING OF TEFLON AF FOR SURFACE PLASMON RESONANCE SENSING." UKnowledge, 2015. http://uknowledge.uky.edu/ece_etds/66.
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Variable pressure electron beam etching and lithography for Teflon AF has been demonstrated. The relation between dose and etching depth is tested under high vacuum and water vapor. High resolution structures as small as 75 nm half-pitch have been resolved. Several simulation tools were tested for surface plasmon excitation. Grating based dual mode surface plasmon excitation has been shown numerically and experimentally.
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Chauvet, Edouard. "Mise en œuvre de superalliages base Nickel par Electron Beam Melting." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREA1084.
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Aujourd’hui, la fabrication additive de pièces métalliques par le procédé EBM (fusion sélective par faisceau d’électrons) concerne essentiellement les alliages de titane et les alliages cobalt-chrome. Une forte demande du secteur aéronautique pousse à étudier la possibilité d'étendre les champs d’application de ce nouveau procédé d'élaboration à d'autres matériaux à haute valeur ajoutée, notamment les superalliages base Nickel.Après la caractérisation des poudres et la description des particularités du procédé EBM (mise en œuvre, paramètres, thermique…), ce travail s'est attaché à développer une méthodologie permettant de structurer l’utilisation d’un nouveau matériau par EBM. Cette méthodologie a dans un premier temps été validée sur un superalliage base Nickel soudable: l'inconel 625.La mise en œuvre d’un superalliage non-soudable a révélé une problématique de fissuration à chaud. Une partie du travail de thèse a été consacrée à la compréhension de l'origine de la fissuration à partir de caractérisations microstructurales multi-échelles. L'étude de la genèse des microstructures et des défauts hérités de la fabrication a permis de proposer des règles de fabrication afin de limiter, et même d'éviter complètement la fissuration. Une adaptation des paramètres opératoires et des stratégies de fusion lors du procédé EBM est utilisée pour générer des microstructures présentant des structures de grains différentes allant de structures équiaxes jusqu'à la fabrication de monocristaux en passant par des structures colonnaires de différentes tailles.Le couplage entre un modèle de solidification prédisant la transition colonnaire-équiaxe et des simulations éléments finis permettant de quantifier les gradients thermiques et les vitesses de solidification a permis d’établir des liens entre les paramètres procédé et les microstructures résultantesOver the last decade, new processing routes based on additive manufacturing (AM) have emerged. Among the AM processes, Electron Beam Melting (EBM) was mainly dedicated to the fabrication of components made of titanium or chromium-cobalt alloys. Aeronautic industry has been a driving force to investigate the possibility to extend the EBM process to other materials and in particular to Ni-based superalloys.The first objective of this work was to develop a methodology to rationalize the use of a new material in the EBM machine. This can be achieved by studying the main characteristics of the EBM process: powder requirements, melting parameters and strategies, thermal aspects.... The methodology was first validated on a weldable Ni-based superalloy: the Inconel 625 grade.The methodology was then extended to the fabrication of a non-weldable Ni-based superalloy, i.e. a grade containing a large fraction of the γ' strengthening phase. Processing such non-weldable superalloys by EBM usually induced cracks in the fabricated components. The microstructures were characterized in order to identify the mechanism at the origin of the cracks. Understanding the mechanism responsible for the development of cracks has allowed to propose new melting strategies limiting or completely avoiding the formation of cracks.Adjusting melting parameters and strategies turns out to be an efficient way for tailoring the grain structure. Equiaxed grains, columnar grains with different sizes as well as single crystals can thus be generated with suitable process parameters.Finally, coupling a solidification model predicting the equiaxed/columnar transition and finite element calculations quantifying the magnitude of the thermal gradient and solidification velocity allowed to establish some links between microstructures and EBM melting parameters
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Blom, Tobias. "Fabrication and Applications of a Focused Ion Beam Based Nanocontact Platform for Electrical Characterization of Molecules and Particles." Doctoral thesis, Uppsala universitet, Experimentell fysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-122940.
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The development of new materials with novel properties plays an important role in improving our lives and welfare. Research in Nanotechnology can provide e.g. cheaper and smarter materials in applications such as energy storage and sensors. In order for this development to proceed, we need to be able to characterize the material properties at the nano-, and even the atomic scale. The ultimate goal is to be able to tailor them according to our needs. One of the great challenges concerning the characterization of nano-sized objects is how to achieve the physical contact to them. This thesis is focused on the contacting of nanoobjects with the aim of electrically characterizing them and subsequently understanding their electrical properties. The analyzed nanoobjects are carbon nanosheets, nanotetrapods, nanoparticles and molecular systems. Two contacting strategies were employed in this thesis. The first strategy involved the development of a focused ion beam (FIB) based nanocontact platform. The platform consists of gold nanoelectrodes, having nanogaps of 10-30 nm, on top of an insulating substrate. Gold nanoparticles, double-stranded DNA and cadmium telluride nanotetrapods have been trapped in the gaps by using dielectrophoresis. In certain studies, the gold electrodes have also been coated with conducting or non-conducting molecules, prior to the trapping of gold nanoparticles, in order to form molecular junctions. These junctions were subsequently electrically characterized to evaluate the conduction properties of these molecular systems. For the purpose of better controlling the attachment of molecules to the nanoelectrodes, a novel route to synthesize alkanedithiol coated gold nanoparticles was developed. The second contacting strategy was based on the versatility of the FIB instrument as a platform for in-situ manipulation and electrical characterization of non-functionalized and functionalized carbon nanosheets, where it was found that the functionalized samples had an increased conductivity by more than one order of magnitude. Both contacting strategies proved to be valuable for building knowledge around contacting and electrical characterization of nanoobjects
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Scott, Kevin. "Fabrication and Characterization of Magnetic Nanostructures." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5437.
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Magnetic permalloy nanostructures were fabricated onto a silicon wafer using electron beam lithography and a liftoff process. The lithography was performed with a Hitachi SU-70 SEM retrofitted with a Nabity NPGS lithography conversion kit. PMMA of 950kDa molecular weight was used as the photoresist. Features were either nanowires, nanodots, or elliptical or rectangular nanostructures. The nanowires had dimensions of 15µm x 200nm x 40nm, the nanodots had diameters of 145nm and thickness of 12nm, and the ellipses and rectangles had dimensions of 110nm x 50nm x 13nm. Characterization of the nanostructures was performed using the same Hitachi SEM as well as a Digital Instruments DI 3100 Nanoscope IIIa AFM used in magnetic force imaging mode. The SEM was used to measure lateral dimensions of the features and to capture images of features for proper documentation and for external simulation studies. The MFM was used to capture magnetic images of the samples to determine the magnetic state of the nanowires or arrays.
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Suard, Mathieu. "Characterization and optimization of lattice structures made by Electron Beam Melting." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI055/document.
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Le récent développement de la Fabrication Additive de pièces métalliques permet d'élaborer directement des structures à partir de modèles 3D. En particulier, la technologie "Electron Beam Melting" (EBM) permet la fusion sélective, couche par couche, de poudres métalliques. Elle autorise la réalisation de géométries très complexes mais apporte de nouvelles contraintes de fabrication.Ce travail se concentre sur la caractérisation géométrique et mécanique de structures treillis produites par cette méthode. Les pièces fabriquées sont comparées au design initial à travers des caractérisations par tomographie aux rayons X. Les propriétés mécaniques sont testées en compression uni-axiale. Pour les poutres de faibles épaisseur, la différence entre la structure numérique et celle fabriquée devient significative. Les écarts au design initial se traduisent pour chaque poutre par un concept de matière mécaniquement efficace. D'un point de vue modélisation, ce concept est pris en compte en remplaçant la poutre fabriquée par un cylindre avec un diamètre mécaniquement équivalent. Ce diamètre équivalent est utilisé dans des simulations et optimisations "réalistes" intégrant ainsi les contraintes de fabrication de la technologie EBM.Différentes stratégies sont aussi proposées pour réduire la proportion de volume "inefficace" et améliorer le contrôle de la taille des poutres, soit en jouant sur les paramètres procédé et les stratégies de fusion, soit en effectuant des post-traitementsThe recent development of Additive Manufacturing for the fabrication of metallic parts allows structures to be directly manufactured from 3D models. In particular, the "Electron Beam Melting" (EBM) technology is a suitable process which selectively melts a powder bed layer by layer. It can build very complex geometries but brings new limitations that have to be quantified.This work focuses on the structural and mechanical characterization of lattice structures produced by such technology. The structural characterization mainly rely on X-ray tomography whereas mechanical properties are assessed by uni-axial compression. The geometry and related properties of the fabricated structures are compared with the designed ones. For small strut size, the difference between the designed structure and the produced one is large enough to impact the desired mechanical properties. The concept of mechanical efficient volume is introduced. For the purpose of simulation, this concept is taken into account by replacing the struts by a cylinder with a textit{mechanical equivalent diameter}. After validation, it has been used into "realistic" simulation and optimization procedures, thus taking into account the process constraints.Post-treatments (Chemical Etching and Electro-Chemical Polishing) were applied on lattice structures to get rid of the inefficient matter by decreasing the surface roughness. The control of the size of the fabricated struts was improved by tuning the process strategies and parameters
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Doutre, Pierre-Thomas. "Comment intégrer et faire émerger des structures architecturées dans l'optimisation de pièces pour la fabrication additive par faisceaux d’électrons." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI039.
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Grâce à la fabrication additive, il est aujourd'hui possible de fabriquer de nouvelles géométries. Les perspectives offertes par les moyens de fabrications conventionnelles et additives sont très différentes. Des propositions de design très contraintes peuvent devenir beaucoup plus libres avec la fabrication additive. Cette liberté qu'elle offre fait émerger une multitude de possibilités. Dans ce manuscrit, nous nous sommes focalisés sur un type particulier de structures (les octetruss) ainsi que sur les moyens de fabrication EBM (Electron Beam Melting) de la société ARCAM. Les travaux présentés dans cette thèse ont été réalisés au sein des laboratoires G-SCOP et SIMAP ainsi qu'en partenariat avec l'entreprise POLY-SHAPE. Ce manuscrit est articulé autour de trois principaux points.Il s'agit tout d'abord de faire émerger des structures treillis lors du processus de conception. Pour cela, deux approches existantes sont détaillées. La première met en œuvre l'optimisation topologique et la seconde s'appuie sur le concept de matériau équivalent. Ensuite deux méthodologies permettent de faire émerger des zones dans lesquelles l'intégration de structures treillis est adaptée. La première consiste à réaliser les différentes zones en s'appuyant sur un champ de contraintes issu d'un calcul Eléments Finis, la seconde se base sur un résultat d'optimisation topologique pour établir les différentes zones. Cette seconde méthodologie est appliquée à un cas d'étude industriel.Ensuite nous étudions comment remplir les différentes zones avec des structures treillis adaptées en nous focalisant tout d'abord sur leur génération. Un accent particulier est porté sur l'intersection des différents barreaux par la mise en place de sphères. Une méthodologie permettant de générer des arrondis est également proposée. Une étude est menée sur l'ensemble des paramètres et informations à considérer pour intégrer une structure treillis à une zone donnée. Cette étude conduit à une proposition de méthodologie qui est appliquée à un cas d'étude industriel.Enfin, les aspects liés à la fabrication sont pris en compte. Pour cela, nous considérons différentes limites du moyen de fabrication EBM pour des structures treillis comme les dimensions maximales réalisables ou les problématiques thermiques. Une étude consistant à prédire la dépoudrabilité des pièces est réalisée. Enfin, des essais mécaniques sont effectués. Nos résultats sont comparés à ceux obtenus dans d'autres travaux. L'impact des arrondis sur le comportement mécanique d'une pièce est discutéThanks to additive manufacturing, it is now possible to manufacture new geometric shapes. The prospects offered by the methods of conventional and additive manufacturing are very different. Highly constrained design proposals can become much freer with additive manufacturing. The freedom it offers brings forward a multitude of possibilities. In this manuscript, we focused on a particular type of structures (the octetruss) as well as the use of EBM (Electron Beam Melting) of ARCAM as a means of manufacturing. The work presented in this thesis was carried out in the laboratories G-SCOP and SIMAP as well as in partnership with the company POLY-SHAPE. This manuscript focuses on three main points.The first of which is the action of emergence of lattice structures during the design process. For this, two existing approaches are detailed. The first uses topological optimization and the second is based on the concept of equivalent material. Following these, there are two methodologies used to identify areas in which the integration of lattice structures is possible and appropriate. The first consists of creating the different zones by relying on a stress field resulting from a finite element calculation, the second establishes the different zones using a topological optimization result. This second methodology is applied to an industrial case study.Secondly, we study how to fill the different areas with appropriate lattice structures by focusing first on their generation. Particular emphasis is placed on the intersection of the various bars by the establishment of spheres. A methodology for generating rounded-shape is also proposed. A study is carried out on all the parameters and information in order to integrate a lattice structure to a given area. This study leads to a proposed methodology that is applied to an industrial case study.Finally, aspects related to manufacturing are taken into account. For this, we consider different limits of the EBM manufacturing and what they mean for lattice structures; such as maximum achievable dimensions or thermal problems. A study to predict powder removal in order to extract the fabricated structure is performed. Mechanical tests are carried out. Our results are compared to those obtained in other works. The impact of curve on the mechanical behavior of a product is discussed
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Lambert, Océane. "Solutions architecturées par fabrication additive pour refroidissement de parois de chambres de combustion." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI048/document.
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En vue de leur refroidissement, les parois de chambres de combustion aéronautiques sont perforées de trous à travers lesquels de l’air plus froid est injecté. La paroi est ainsi refroidie par convection et un film isolant est créé en surface chaude (film cooling). Cette thèse a pour objectif d’utiliser les possibilités de la fabrication additive pour proposer de nouvelles solutions architecturées qui permettraient d’augmenter les échanges de chaleur internes et d’obtenir ainsi de meilleures efficacités de refroidissement.La première approche consiste à élaborer de nouveaux designs de plaques multiperforées par Electron Beam Melting (EBM) et Selective Laser Melting (SLM) aux limites de résolution des procédés. Les architectures sont caractérisées en microscopie, en tomographie X et en perméabilité. Des simulations aérothermiques permettent de mettre en évidence l’effet de ces nouveaux designs sur l’écoulement et les échanges de chaleur, et de proposer des voies d’amélioration de la géométrie.La deuxième approche consiste à élaborer de façon simultanée une pièce architecturée par EBM, avec des zones denses et poreuses. A partir d’analyse d’images associée à une cartographie EBSD grand champ, il est possible de remonter aux mécanismes de formation du matériau poreux et de relier la perméabilité et la porosité aux paramètres procédé. Afin de favoriser le film cooling, il pourrait être avantageux que les zones microporeuses soient orientées dans le sens de l’écoulement. Pour ce faire, un nouveau procédé dénommé Magnetic Freezing, où des poudres métalliques forment une structure orientée par un champ magnétique, est mis au point.Les diverses solutions développées durant cette thèse sont testées sur un banc aérothermique. Les essais montrent qu’elles offrent un refroidissement plus efficace et plus homogène que la référence industrielle. Enfin, de premiers tests en combustion sur l’une des structures retenues, plus légère et plus perméable que la référence, montrent qu’il s’agit d’une solution aussi efficace à un débit traversant donné, et donc a priori plus efficace à une surpression donnéeCombustion chamber walls are perforated with holes so that a cooling air flow can be injected through them. The wall is cooled by convection and an insulating film is created on the hot surface (film cooling). This PhD thesis aims to use the possibilities of additive manufacturing to provide new architectured solutions that could enhance the internal heat exchanges, and lead to a higher cooling effectiveness.The first approach is to develop new designs of multiperforated walls by Electron Beam Melting (EBM) and Selective Laser Melting (SLM) used at the resolution limits of the processes. They are characterized by microscopy, X-ray tomography and permeability tests. Some aerothermal simulations help understanding the effects of these new designs on the flow and on heat exchanges. These results lead to a geometry adaptation.The second approach is to simultaneously manufacture an architectured part with dense and porous zones by EBM. Thanks to image analysis combined with large field EBSD, it is possible to investigate the mechanisms leading to the porous zones and to link them to permeability and porosity. The film cooling effect could be favoured by the orientation of pores towards the cooling flow. Therefore, a new powder-based manufacturing process named Magnetic Freezing, where metallic powders organize into an oriented structure thanks to a magnetic field, is developed.The various solutions studied during this thesis are tested on an aerothermal bench. They all show a more efficient and homogeneous cooling than the industrial reference. Some first tests on one of the selected solutions are performed on a combustion bench. This lighter and more permeable structure proves to be a solution as efficient as the industrial reference at a given flow rate. It should therefore be a more efficient solution for a given overpressure
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Zhang, Ziyang. "Silicon-based Photonic Devices : Design, Fabrication and Characterization." Doctoral thesis, Stockholm : Mikroelektronik och tillämpad fysik, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4647.
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Persenot, Théo. "Fatigue of Ti-6Al-4V thin parts made by electron beam melting." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI117/document.
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De nos jours, il est crucial pour les industries de réduire leur consommation énergétique. Pour les industries du transport, cela peut se faire par le biais de l’allègement des pièces de structure. Dans ce contexte, les structures cellulaires représentent une des solutions les plus prometteuses. Grâce au développement de la fabrication additive, l’élaboration de telles géométries complexes n’est plus un frein à leur utilisation. Néanmoins, cette dernière restera limitée tant que les propriétés mécaniques – et plus particulièrement la résistance en fatigue pour les pièces aéronautiques – ne seront pas maîtrisées. Ce travail de thèse a pour objectif de déterminer les mécanismes qui gouvernent le comportement en fatigue de ces structures cellulaires. Pour cela, le travail s’est focalisé sur l’élement unitaire les constituant : la poutre. Des éprouvettes minces représentatives de la poutre ont été élaborées par Electron Beam Melting puis caractérisées à l’état brut de fabrication à l’aide de différentes techniques (tomographie aux rayons X, microscopie optique et électronique, …). Leurs propriétés statique et cyclique en traction ont ensuite été évaluées. L’état de surface et en particulier les défauts d’entaille ont été identifiés comme responsable de la perte de résistance. L’impact de ces défauts sur la résistance en fatigue a été prédit avec succès par le biais de diagrammes de Kitagawa. L’impact de l’orientation de fabrication a également été observé et prédit. Différents post-traitements ont ensuite été utilisés afin d’améliorer ces propriétés. Le polissage chimique et le grenaillage ultrasonique ont réduit de manière significative la criticité des défauts de surface ce qui a grandement amélioré les propriétés mécaniques des éprouvettes, jusqu’à se rapprocher de celles obtenues après usinage. Par ailleurs, la compression isostatique à chaud a provoqué la fermeture de l’entièreté des défauts internes ainsi qu’un grossissement de la microstructure. Ce dernier point permet une amélioration supplémentaire de la performance en fatigue une fois combiné avec un traitement de surface. Enfin, une méthode permettant de détecter automatiquement tous les défauts d’entailles et de déterminer leur criticité et leur influence sur la résistance en fatigue a été proposée et discutée. Elle a ensuite été appliquée avec succès aux échantillons attaqués chimiquement mais des modifications demeurent nécessaire pour l’appliquer à d’autres états de surfaceNowadays, reducing the energy consumption is crucial for most of the industries. For transportation industries, it can be achieved through weight reduction. In this context, cellular structures turn out to be one of the most efficient solution. Thanks to the development of additive manufacturing, producing such complex geometries is no longer an issue. However, their use will remain limited as long as their fatigue performances are not known. This PhD work aimed at understanding the mechanisms that govern the fatigue behaviour of such cellular structures. It was first decided to focus on their unitary element, i.e. a single strut. Single struts samples were manufactured by Electron Beam Melting and then characterized in as-built conditions using different experimental techniques (X-ray tomography, optical and electron microscopy, etc.). Their static and cyclic tensile properties were then evaluated. The rough surface and in particular notch-like defects were found to be responsible for the knockdown of the mechanical properties. Regarding the fatigue resistance, their detrimental impact was predicted using Kitagawa diagrams. It also enabled to explain the impact of the build orientation. Different post-treatments were used in order to improve these mechanical properties. Chemical etching and ultrasonic shot peening (USP) significantly reduced the severity of surface defects of as-built thin struts and thus increased their mechanical properties. After USP, the fatigue properties of machined samples were almost matched. Hot Isostatic Pressing lead to the closure of all internal defects and to the coarsening of the microstructure. When combined with one of the surface treatments, the fatigue properties were further improved. Finally, a method enabling to systematically and automatically extract from the surface the most critical defects and quantitatively analyze their influence on fatigue life was proposed and discussed. It was successfully applied to chemical etched samples but improvements are mandatory for other surface conditions
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Hiricoiu, Alexandre. "Contribution à l'analyse expérimentale et numérique pour l'élaboration d'absorbeurs d'énergie obtenus par procédés de fabrication additive." Thesis, Valenciennes, 2018. http://www.theses.fr/2018VALE0011.
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La rentabilité des hélicoptères de transport civil est un paramètre clé qui oblige les avionneurs à toujours repousser les limites en termes d’optimisation des structures. Les nouvelles générations d’appareils devront parcourir des distances plus longues et avoir des capacités de transport plus grandes. Le gain en masse sur les équipements à bord des appareils est donc un facteur déterminant pour atteindre les objectifs de performances accrues pour le futur. Les travaux de recherche menés durant la thèse sont à l’initiative de l’équipementier aéronautique Zodiac Seats France, leader français sur le marché des sièges techniques pour hélicoptères civils. L’objectif souhaité de l’entreprise est le développement à moyen terme d’un siège passager ayant un gain de masse ciblé à 50% des équipements actuels. Cette amélioration n’est aujourd’hui envisageable qu’à travers une rupture technologique avec les solutions déjà existantes. Les nouveaux procédés notamment en matière de fabrication additive permettent à ce jour d’envisager des réalisations de structures innovantes à forme complexe. Le choix de la technologie de fabrication additive EBM « Electron Beam Melting » est fixé.La Recherche menée ici, vise à assurer la sécurité des futurs sièges en cas de crash, grâce à l’étude de nouvelles solutions techniques pour permettre une absorption optimale d’énergie lors de l’impact. Les travaux présentés s’organisent en trois volets. Le premier concerne la caractérisation en traction statique et dynamique ainsi que la modélisation numérique du titane Ti–6Al–4V obtenu par fabrication additive EBM. Pour cela un protocole expérimental ainsi qu’un plan d’expérience ont été définis. Le second volet vise à valider les propriétés matériau établies par le biais d’essais et de simulations à l’échelle de structures complexes dans un objectif de fournir au concepteur un outil de modélisation numérique permettant un dimensionnement efficace. Enfin, le troisième volet présente la stratégie développée au cours de la thèse pour permettre à l’aide d’un outil d’optimisation la définition numérique de futures formes de structures capables d’absorber un maximum d’énergie dans un espace géométrique disponibleThe profitability of civil transport helicopters is a key parameter that forces aircraft manufacturers to always push forward innovation and design optimization. Next generation of aircraft must be able to fly longer and have increased transport capacities. Weight reduction on in-flight equipment is a critical factor to achieve better performances in the future. The research work carried out during the PhD thesis was initiated by the aeronautical equipment manufacturer Zodiac Seats France, the French leader in the market of technical seats for civil helicopters. The desired objective of the company is the mid-term development of a passenger seat with a targeted mass reduction of 50% to current equipments. This improvement is only possible today with technological breakthrough. New processes, particularly in the field of additive manufacturing, allow nowadays the production of innovative structures with complex shapes. The choice of additive manufacturing technology EBM "Electron Beam Melting" is fixed. The research conducted here aims to ensure the safety of future seats in the event of a crash, thanks to the study of new technical solutions to allow optimal absorption of energy at impact. The works presented are organized in three parts. The first concerns the static and dynamic tensile characterization as well as the numerical modeling of titanium Ti-6Al-4V obtained by additive manufacturing EBM. For this purpose, an experimental protocol and an experimental plan have been defined. The second part aims to validate the material properties established by means of tests and simulations at the scale of complex structures in order to provide the designer with a numerical modeling tool allowing efficient dimensioning. Finally, the third part presents the strategy developed during the thesis to help in optimizing, through the numerical simulation, the future structures capable of absorbing a maximum of energy for a given geometrical space
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Hoffman, Galen Brandt. "Direct Write of Chalcogenide Glass Integrated Optics Using Electron Beams." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1322494007.
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Chougrani, Laurent. "Modélisation avancée de formes complexes de pièces mécaniques pour lesprocédés de fabrication additive." Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0054.
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Les procédés de fabrication additive ont connus un fort essor dans les dernières décennies et entament aujourd'hui leur phase d'industrialisation pérenne. L'industrie, dans un souci d'améliorer sans cesse le ratio masse/rigidité des systèmes qu'elle produit (notamment l'industrie aéronautique), a pris conscience du potentiel de ces technologies à produire des structures plus complexes que les procédés classiques. Elle cherche aujourd'hui à tirer profit de ce potentiel pour alléger encore plus les pièces produites en utilisant notamment des géométries de type réseaux ou alvéolaires (Lattice en anglais). Les travaux présentés dans ce manuscrit ont pour but de proposer une méthodologie, des modèles et des outils permettant la conception, le dimensionnement et l'optimisation de telles structures en vue de leur fabrication par procédés additifs. Le framework proposé peut être résumé par les huit étapes ci-dessous:- Importation de l'espace de conception, comprenant également les cas de chargement.- Optimisation topologique sur l'espace de conception.- Reconstruction de la géométrie, appelée primitive, qui servira de support à l'insertion du réseau.- Calcul par éléments finis qui peut être réalisé pour s'assurer de la bonne tenue mécanique.- Définition de la topologie du réseau, par l'intermédiaire d'un graphe 3D.- Déformation du réseau et optimisation mécanique du réseau.- Reconstruction des volumes.- Préparation des fichiers de données et impression 3DAdditive manufacturing processes have been quickly growing those past decades and are now getting to their sustainable industrial. Industry has been caring about the mass to rigidity ratio of the structures it produces (especially in aeronautics), and is now acknowledging the potential of additive processes to produce more complex shapes than classical processes. Industry is now trying to take advantage of this potential by designing highly complex structures like lattices or metal foams. The work that is presented in this document propose a methodology, models and numerical tools allowing the conception, dimensioning and optimization of such structures through additive manufacturing. The proposed framework can be describe through the height following steps:- Importing the design space and the technical requirement (load cases).- Topology optimization of the design space- Geometry reconstruction to create a primitive which will be the lattice insertion area.- Finite elements computation to ensure that the structure meets the requirements.- Lattice topology definition using 3D graphs.- Lattice deformation and optimization.- Creation of the volumes around the lattice.- Printing file creation and 3D printing
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Laughlin, Kevin Robert. "Thin Film Carbon Nanofuses for Permanent Data Storage." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6793.
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We have fabricated nanofuses from thin-film, arc-evaporation carbon for use in permanent data storage. Thin film carbon fuses have fewer fabrication barriers and retain the required resistivity and structural stability to work as a data storage medium. Carbon thin films were characterized for their electrical, microstructural, and chemical bonding properties. Annealing the thin-film carbon in an argon environment at 400°C reduced the resistivity from about 4*10-2 Ω cm as deposited down to about 5*10-4 Ω cm, allowing a lower blowing voltage. Nanofuses with widths ranging from 200 nm down to 60 nm were fabricated and tested. They blow with voltages between 2 V and 5.5 V, and the nanofuses remain stable in both a "1" and a "0" state under a constantly applied read voltage of 1 volt for over 90 hours, corresponding to a cumulative time of >1012 reads.
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Ruess, Frank Joachim Physics Faculty of Science UNSW. "Atomically controlled device fabrication using STM." Awarded by:University of New South Wales. Physics, 2006. http://handle.unsw.edu.au/1959.4/24855.
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We present the development of a novel, UHV-compatible device fabrication strategy for the realisation of nano- and atomic-scale devices in silicon by harnessing the atomic-resolution capability of a scanning tunnelling microscope (STM). We develop etched registration markers in the silicon substrate in combination with a custom-designed STM/ molecular beam epitaxy system (MBE) to solve one of the key problems in STM device fabrication ??? connecting devices, fabricated in UHV, to the outside world. Using hydrogen-based STM lithography in combination with phosphine, as a dopant source, and silicon MBE, we then go on to fabricate several planar Si:P devices on one chip, including control devices that demonstrate the efficiency of each stage of the fabrication process. We demonstrate that we can perform four terminal magnetoconductance measurements at cryogenic temperatures after ex-situ alignment of metal contacts to the buried device. Using this process, we demonstrate the lateral confinement of P dopants in a delta-doped plane to a line of width 90nm; and observe the cross-over from 2D to 1D magnetotransport. These measurements enable us to extract the wire width which is in excellent agreement with STM images of the patterned wire. We then create STM-patterned Si:P wires with widths from 90nm to 8nm that show ohmic conduction and low resistivities of 1 to 20 micro Ohm-cm respectively ??? some of the highest conductivity wires reported in silicon. We study the dominant scattering mechanisms in the wires and find that temperature-dependent magnetoconductance can be described by a combination of both 1D weak localisation and 1D electron-electron interaction theories with a potential crossover to strong localisation at lower temperatures. We present results from STM-patterned tunnel junctions with gap sizes of 50nm and 17nm exhibiting clean, non-linear characteristics. We also present preliminary conductance results from a 70nm long and 90nm wide dot between source-drain leads which show evidence of Coulomb blockade behaviour. The thesis demonstrates the viability of using STM lithography to make devices in silicon down to atomic-scale dimensions. In particular, we show the enormous potential of this technology to directly correlate images of the doped regions with ex-situ electrical device characteristics.
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Vayre, Benjamin. "Conception pour la fabrication additive, application à la technologie EBM." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI096/document.
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Les procédés de fabrication additive sont aujourd'hui de plus en plus utilisés dans l'industrie. Parmi les différentes technologies existantes, les procédés additifs métalliques, et notamment les procédés en couches, sont les plus prometteurs pour la conception de produits mécaniques. Des travaux ont été menés sur la thématique de la conception de produits réalisés par ces moyens, il traitent principalement du choix du procédé le plus adapté, de l'optimisation de formes ou présentent des cas de reconception. Il n'existe cependant pas de démarche globale de conception de produits qui permettent de prendre en compte les spécificités des procédés additifs en couches, notamment leurs contraintes de fabrication.Lors de ce travail de thèse, les changements que ces procédés introduisent dans le domaine des possibles en conception de produits ont été montrés et illustrés par des pièces réalisées par EBM. De nouvelles opportunités s'offrent au concepteur, comme l'accès à l'ensemble du volume de fabrication, la facilité de réalisation de pièces complexes, la possibilité de réaliser des treillis tridimensionnels et la capacité de produire des mécanismes sans assemblage. Les contraintes de fabrication de ces procédés sont spécifiques. Les phénomènes thermiques lors de la fabrication ont une incidence sur la fabricabilité et la qualité des pièces. La phase de retrait de poudre impose quant à elle des contraintes d'accessibilités. Pour prendre en compte cette évolution, il est nécessaire de concevoir spécifiquement les pièces pour la fabrication additive.Le procédé EBM est au centre du travail réalisé. Il s'agit d'un moyen de fabrication additive en couches, par fusion, à l'aide faisceau d'électrons. Les phénomènes thermiques, qui peuvent causer déformations et mauvaise intégrité de la matière, l'opération de dépoudrage et la problématique de la qualité des pièces fabriquées par EBM ont fait l'objet de caractérisations expérimentales. La durée de fabrication et le coût de revient technique des pièces réalisées par EBM ont également été étudiés, afin d'établir la relation entre durée, coût et géométrie des pièces.Pour de prendre en compte les contraintes explicitées auparavant, et pour bénéficier des importantes libertés que ce procédé offre aux concepteurs, une démarche de conception a été proposée. Cette démarche consiste à générer une ou plusieurs géométries initiales, soit directement par le concepteur, soit par l'utilisation d'outils d'optimisation topologique, à partir de données extraites du cahier des charges. Une fois le balançage de la pièce choisi (en prenant en compte les contraintes de fabrication, le tolérancement de la pièce et la productivité de la fabrication), la pièce est modélisée en incluant un jeu de paramètres pour effectuer une optimisation paramétrique. Cette optimisation permet de dimensionner la pièce, tout en prenant en compte les contraintes de fabrication. A l'issue de cette phase d'optimisation, la géométrie finale est obtenue en prenant en compte les exigences des opérations de parachèvement éventuelles et en définissant les supports, s'ils sont nécessaires. Cette démarche a été illustrée par la reconception de deux pièces mécaniques qui répondent aux exigences de leur cahier des charges fonctionnel, sont fabricables à l'aide du procédé EBM et offrent des gains de masse importants.Enfin, un chapitre particulier est consacré aux perspectives mises en évidence (et ayant parfois fait l'objet de travaux préliminaires) à l'occasion de ce travail de thèseNowadays, the use of Additive Manufacturing processes keeps growing in the industry. Among the numerous kinds of AM processes, metallic additive manufacturing processes, and metallic Additive Layer Manufacturing in particular, are the most interesting from a mechanical designer point of view. Several research studies have been conducted on the topic of Design For Additive Manufacturing, mostly discussing the choice of AM processes or presenting the redesign of parts. There is no specific design methodology for ALM processes that takes their specificities into account.During this PhD thesis, the changes that ALM processes bring to the design space were investigated. The designer has the opportunity to easily manufacture thin parts, complex parts, lattice structures or mechanisms that don't need any assembly. These processes also have specific manufacturing constraints compared to conventional processes. The heat dissipation is the most important factor since it can cause distortions and porosities. Powder removal, surface and geometrical quality also need to be considered during design. A specific design for additive manufacturing methodology is necessary to take these changes into account.This work focuses on the Electron Beam Manufacturing process. Experiments were conducted and analyzed to assess the manufacturability regarding the thermal phenomena (during melting), the powder removal and the quality of the parts produced by EBM. The impact of the part geometry on manufacturing duration and manufacturing cost was also established.In order to use allow designers to use these pieces of information, we suggested a designing methodology. From the requirements of the parts, one or several parts are generated by the designer or by using topological optimization tools. The orientation of the part inside the manufacturing space is set before designing a refined parametric geometry. This parametric geometry is optimized in order to meet the user requirements as well as the EBM requirements. The last step is the modification of the geometry to comply with the finishing operations (machining allowances for example) and the placement of supports, if needed. This methodology was illustrated with the redesign of two example parts and showed important mass savings from the parts (while meeting user and process requirements).The prospects discovered and highlighted during this work, some of which were preliminary investigated, are presented in a specific chapter
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Vollnhals, Florian [Verfasser], and Hubertus [Akademischer Betreuer] Marbach. "Exploring Electron Beam Induced Surface Activation for the Fabrication of well-defined Nanostructures: On the Role of Catalytic Processes, Substrates and Precursors. / Florian Vollnhals. Gutachter: Hubertus Marbach." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2015. http://d-nb.info/107547910X/34.
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Tu, Fan [Verfasser], and Hubertus [Gutachter] Marbach. "On the Lithographic Fabrication of Fe and Co Nanostructures via Focused Electron/Photon Beam Induced Processing: Properties and Applications of the Structures / Fan Tu ; Gutachter: Hubertus Marbach." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2017. http://d-nb.info/1150964308/34.
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Preischl, Christian [Verfasser], Hubertus [Akademischer Betreuer] Marbach, Hubertus [Gutachter] Marbach, and Jörg [Gutachter] Libuda. "Exploring Electron Beam Induced Processing with Metal-Organic and Organic Materials for the Fabrication of Hybrid Nanostructures / Christian Preischl ; Gutachter: Hubertus Marbach, Jörg Libuda ; Betreuer: Hubertus Marbach." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2021. http://d-nb.info/1241332681/34.
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Smith, Gabriel. "PARAMETERS AFFECTING THE RESISTIVITY OF LP-EBID DEPOSITED COPPER NANOWIRES." UKnowledge, 2018. https://uknowledge.uky.edu/ece_etds/114.
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Electron Beam Induced Deposition (EBID) is a direct write fabrication process with applications in circuit edit and debug, mask repair, and rapid prototyping. However, it suffers from significant drawbacks, most notably low purity. Work over the last several years has demonstrated that deposition from bulk liquid precursors, rather than organometallic gaseous precursors, results in high purity deposits of low resistivity (LPEBID). In this work, it is shown that the deposits resulting from LP-EBID are only highly conductive when deposited at line doses below 25μC/cm. When the dose exceeds this value, the resulting structure is highly porous providing a poor conductive pathway. It is also shown that beam current has no significant effect on the resistivity of the deposits. Nanowires with resistivity significantly lower than the previous best result of 67μΩ•cm were achieved, with the lowest resistivity being only 6.6μΩ•cm, only a factor of 4 higher than that bulk copper of 1.7μΩ•cm.
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Gonzalez, Martinez Ignacio Guillermo [Verfasser], Gianaurelio [Akademischer Betreuer] [Gutachter] Cuniberti, Mark Hermann [Akademischer Betreuer] [Gutachter] Rümmeli, and Kornelius [Akademischer Betreuer] [Gutachter] Nielsch. "Novel thermal and electron-beam approaches for the fabrication of boron-rich nanowires / Ignacio Guillermo Gonzalez Martinez ; Gutachter: Gianaurelio Cuniberti, Mark Hermann Rümmeli, Kornelius Nielsch ; Gianaurelio Cuniberti, Mark Hermann Rümmeli, Kornelius Nielsch." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://d-nb.info/1130092658/34.
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Gonzalez, Martinez Ignacio Guillermo [Verfasser], Gianaurelio [Akademischer Betreuer] Cuniberti, Mark Hermann Akademischer Betreuer] [Gutachter] Rümmeli, and Kornelius [Akademischer Betreuer] [Nielsch. "Novel thermal and electron-beam approaches for the fabrication of boron-rich nanowires / Ignacio Guillermo Gonzalez Martinez ; Gutachter: Gianaurelio Cuniberti, Mark Hermann Rümmeli, Kornelius Nielsch ; Gianaurelio Cuniberti, Mark Hermann Rümmeli, Kornelius Nielsch." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-218019.
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Sekkaki, Noureddine. "Etude theorique et experimentale de la nanolithographie par electrons." Toulouse 3, 1987. http://www.theses.fr/1987TOU30147.
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Dans le cadre de ce memoire nous avons etudie sur le plan theorique l'influence de la tension acceleratrice des electrons incidents sur les dimensions des traces obtenus. En s'appuyant sur des resultats obtenus anterieurement nous avons simule pour une methode de monte-carlo, les trajectoires des particules incidents. Nous avons pu ainsi localiser l'energie deposee par les electrons incidents les electrons retrodiffuses par le substrat et les electrons secondaires. L'ensemble des resultats montre l'interet theorique presente par l'emploi de tensions plus elevees (100 kev) que celles habituellement utilisees en microlithographie (20 a 50 kev). Afin de preciser les differents mecanismes intervenant dans la modification de la resine nous avons etudie a l'aide d'un analyseur de pertes d'energie des electrons l'evolution au cours de l'irradiation du spectre obtenu. Les performances obtenues sont illustrees par differentes gravures representant le trace de motifs realises dans une couche de pmma de 0,5 micron d'epaisseur, avec des lignes de 0,4 micron de large
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James, Daniel. "Fabrication and electrical characterisation of quantum dots : uniform size distributions and the observation of unusual electrical characteristics and metastability." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/fabrication-and-electrical-characterisation-of-quantum-dots-uniform-size-distributions-and-the-observation-of-unusual-electrical-characteristics-and-metastability(01bb9182-5290-4ad1-b6a4-3aed3970dbcf).html.
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Quantum dots (QDs) are a semiconductor nanostructure in which a small island of one type of semiconductor material is contained within a larger bulk of a different one. These structure are interesting for a wide range of applications, including highly efficient LASERs, high-density novel memory devices, quantum computing and more. In order to understand the nature of QDs, electrical characterisation techniques such as capacitance-voltage (CV) profiling and deep-level transient spectroscopy (DLTS) are used to probe the nature of the carrier capture and emission processes. This is limited, however, by the nature of QD formation which results in a spread of sizes which directly affects the energy structure of the QDs. In this work, I sought to overcome this by using Si substrates patterned with a focused ion beam (FIB) to grow an array of identically-sized Ge dots. Although I was ultimately unsuccessful, I feel this approach has great merit for future applications.In addition, this thesis describes several unusual characteristics observed in InAs QDs in a GaAs bulk (grown by molecular beam epitaxy-MBE). Using conventional and Laplace DLTS, I have been able to isolate a single emission transient. I further show an inverted relation between the emission rate and the temperature under high field (emissions increase at lower temperatures). I attribute this to a rapid capture to and emission from excited states in the QD. In addition, I examine a metastable charging effect that results from the application of a sustained reverse bias and decreases the apparent emission rate from the dots. I believe this to be the result of a GaAs defect with a metastable state which acts as a screen, inhibiting emission from the dots due to an accumulation of charge in the metastable state. These unusual characteristics of QDs require further intensive work to fully understand. In this work I have sought to describe the phenomena fully and to provide hypotheses as to their origin.
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Mazuir, Clarisse. "Design, fabrication, and testing of high-transparency deep ultra-violet contacts using surface plasmon coupling in subwavelength aluminum meshes." Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4979.
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The present work aims at enhancing the external quantum efficiencies of ultra-violet (UV) sensitive photodetectors (PDs) and light emitting diodes (LEDs)for any light polarization. Deep UV solid state devices are made out of AlGaN or MgZnO and their performances suffer from the high resistivity of their p-doped regions. They require transparent p-contacts; yet the most commonly used transparent contacts have low transmission in the UV: indium tin oxide (ITO) and nickel-gold (Ni/Au 5/5 nms) transmit less than 50% and 30% respectively at 300 nm. Here we investigate the use of surface plasmons (SPs) to design transparent p-contacts for AlGaN devices in the deep UV region of the spectrum. The appeal of using surface plasmon coupling arose from the local electromagnetic field enhancement near the metal surface as well as the increase in interaction time between the field and semiconductor if placed on top of a semiconductor. An in/out-coupling mechanism is achieved by using a grating consisting of two perpendicularly oriented sets of parallel aluminum lines with periods as low as 250 nm. The incident light is first coupled into SPs at the air/aluminum interface which then re-radiate at the aluminum/AlGaN interface and the photons energy is transferred to SP polaritons (SPPs) and back to photons. High transmission can be achieved not only at normal incidence but for a wider range of incident angles. A finite difference time domain (FDTD) package from R-Soft was used to simulate and design such aluminum gratings with transparency as high as 100% with tunable peak wavelength, bandwidth and angular acceptance. A rigorous coupled wave analysis (RCWA) was developed in Matlab to validate the FDTD results. The high UV transparency meshes were then fabricated using an e-beam assisted lithography lift-off process. Their electrical and optical properties were investigated. The electrical characterization was very encouraging; the sheet resistances of these meshes were lower than those of the conventionally used transparent contacts. The optical transmissions were lower than expected and the causes for the lower measurements have been investigated. The aluminum oxidation, the large metal grain size and the line edge roughness were identified as the main factors of inconsistency and solutions are proposed to improve these shortcomings. The effect of aluminum oxidation was calculated and the passivation of aluminum with SiO[sub2] was evaluated as a solution. A cold deposition of aluminum reduced the aluminum grain size from 60 nm to 20 nm and the roughness from 5 nm to 0.5 nm. Furthermore, replacing the conventional lift-off process by a dry back-etch process led to much smoother metal line edges and much high optical transparency. The optical measurements were consistent with the simulations. Therefore, reduced roughness and smooth metal line edges were found to be especially critical considerations for deep UV application of the meshes.ID: 029810223; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 140-145).
Ph.D.
Doctorate
Optics and Photonics
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Croset, Guillaume. "Caractérisation in situ par imagerie proche infrarouge en fabrication additive "fusion sur lit de poudre par faisceau d'électrons." Thesis, Université Grenoble Alpes, 2021. http://www.theses.fr/2021GRALI018.
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Le procédé de fabrication additive par fusion sur lit de poudre par faisceau d’électrons (E-PBF) permet la réalisation de pièces métalliques par fusion sélective de couches successives. Il peut cependant générer des défauts dans les pièces fabriquées. Afin d’améliorer la fiabilité de ce procédé, le besoin de contrôles in situ (pendant la fabrication) est devenu une exigence forte. L’objectif de ce travail est de mettre en place des stratégies de suivi in situ de la fabrication additive E-PBF. L’outil sélectionné est une caméra proche infrarouge (NIR) permettant d’obtenir des images des pièces en cours de fabrication. Un dispositif expérimental permettant de réaliser les acquisitions à l’aide d’une caméra proche infrarouge de façon automatisée a été mis en place en prenant en compte l’environnement contraignant (haute température, vide, dépôt de métal sur les parois). Deux stratégies de contrôle sont proposées. La première vise à prendre une image de chaque couche fabriquée, en l’occurrence à l’issue de l’étape de fusion. Des routines d’analyse d’images ont été développées et permettent d’identifier et de localiser les défauts (distorsions géométriques, porosités) à partir de leur signature thermique sur les images NIR. Une méthode de contrôle non destructif (tomographie aux rayons X) permet de valider la détection des défauts internes. La seconde stratégie de caractérisation consiste à réaliser l’acquisition d’images en continu afin d’analyser l’évolution temporelle des niveaux de gris, cette dernière apportant des informations reliées aux changements de température. Une méthodologie permettant de détecter, voire d’anticiper certains défauts liés à l’apport d’énergie délivrée par le faisceau d’électrons est proposée. Les deux stratégies de caractérisation doivent permettre de repérer les défauts au plus vite afin de mettre en place une action corrective dans la cadre d’un futur contrôle du procédé par une boucle ferméeElectron beam Powder Bed Fusion (E-PBF) is an additive manufacturing process that allows metallic parts to be built by selectively melting successive layers of powder. However, this process can generate defects in the fabricated parts. To improve the reliability of this process, there is a need to develop in-situ monitoring imaging techniques. The main objective of this work is to set up strategies to characterize in-situ the E-PBF process. The selected tool is a near-infrared (NIR) camera employed to obtain images of the parts being manufactured. The first part of the work has been dedicated to setting up an experimental device allowing to acquire near-infrared images in an automated way and by taking into account the constrained environment of E-PBF (high temperature, vacuum, metal deposit on the walls). Two strategies of in-situ monitoring of E-PBF are suggested. The first one aims at taking one image per layer, just after the melting stage. Image analysis routines were developed and allow to identify and determine the spatial distribution of the defects (geometrical distortions, porosity) from their thermal signatures on the NIR-images. The detection of internal defects is validated with a non-destructive characterization (X-rays computed tomography). The second strategy consists of carrying out continuous image acquisition to analyze the temporal evolution of the grey level which is directly related to temperature changes. A methodology allowing to detect, even to anticipate given defects related to the energy delivered by the electron beam has been proposed. Those two approaches should allow the defects to be identified as quickly as possible to apply a correction within the framework of future closed-loop process control
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Ciprelli, Jean-Louis. "Application de polymères conducteurs en microlithographie : évaluation de polythiophènes comme résines négatives électrosensibles pour la réalisation de masques à décalage de phase." Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10217.
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L'utilisation de masques a decalage de phase (mdp) en lithographie uv profonds semble indispensable pour l'obtention d'une resolution de 0. 1 micron, pour les generations futures de circuits integres. La mise au point de procedes de fabrication simplifies de masques apparait desormais comme un enjeu technologique important. Les mdp sont principalement realises par ecriture directe sous faisceau d'electrons. La limitation principale de cette lithographie est l'alteration de la precision d'ecriture du faisceau electronique. En effet, l'accumulation de charges a la surface de la resine electrosensible isolante provoque la deviation du faisceau d'electrons. L'analyse des differents procedes existants a montre que l'utilisation d'un polymere conducteur et electrosensible, comme dephaseur optique permet d'apporter des ameliorations au niveau de la mise en uvre du materiau conducteur et de l'etape lithographique. Notre choix s'est porte sur la famille des polythiophenes, polymeres conducteurs reticulables sous faisceau d'electrons. L'aspect technologique de ce travail a consiste a mettre au point les differents etapes du procede. L'etat conducteur du polymere est obtenu par dopage des films a l'aide de composes organiques specifiques permettant d'eviter toute contamination metallique, redhibitoire en microelectronique. La mise au point de l'etape lithographique a permis d'identifier des parametres critiques tels que la synthese du polymere ou la nature du developpeur. Enfin, une etude de vieillissement sous uv profonds du materiau reticule a montre les limites d'utilisation en lithographie
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Neradovskiy, Maxim. "Guides d’ondes dans un cristal de niobate de lithium périodiquement polarisé : fabrication et étude par des techniques de microscopie à sonde locale." Thesis, Nice, 2016. http://www.theses.fr/2016NICE4035/document.
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Nous avons étudié l'influence de la fabrication de guides d'ondes optiques par échange protonique doux(SPE) sur les cristaux de niobate de lithium (LN) polarisé périodiquement et nous avons montré que,dans certains cas, ce processus conduit à la création de nanodomaines en surface. Ces nanodomaines enforme d'aiguille peuvent être responsables de la réduction de l'efficacité de conversion non linéaireobservée dans les guides qui sont affectés. Nous avons également étudié l'influence de différents typesd'échange protonique sur la formation, par application d'un champ électrique, de domaines dans le LNcongruent. Cette étude montre que le seuil de nucléation peut être fortement réduit par la présence duguide d'onde et que l'apparition et le développement des domaines en forme de traits est fortementmodifiée. Elle montre également que la fusion des nanodomaines existants au voisinage des parois dedomaine aboutit à la formation de parois élargies et de domaines en forme de dendrites. En irradiantavec un faisceau d'électrons la surface Z- d'un échantillon de LN préalablement soumis à un échangeprotonique doux et recouvert d'une couche de résine électronique, nous avons réussi à former desdomaines avec des formes arbitraires. Par cette technique, nous avons fabriqué des domainespériodiques d'excellente qualité dans des cristaux présentant des guides canaux SPE. Des expériences degénération de deuxième harmonique dans ces guides nous ont permis d'obtenir des efficacités deconversion de 48%/W.cm2 ce qui est conforme aux prédictions ainsi que la forme des spectres d'accordde phase que nous avons observés. Ceci démontre tout l'intérêt de ce processusThe investigation of influence of the soft proton exchange (SPE) optical waveguide (WG) creation onperiodically poled lithium niobate (PPLN) has been done. It has been shown that the WG fabricationprocess can induce the formation of needle like nanodomains, which can be responsible for thedegradation of the nonlinear response of the WG created in PPLN crystals. The domain structure (DS)evolution has been studied in congruent lithium niobate (LN) crystals with surface layers modified bythree different proton exchange techniques. The significant decrease of the nucleation threshold fieldand qualitative change of domain rays nucleation and growth have been revealed. The formation of abroad domain boundary and dendrite domain structure as a result of nanodomains merging in front ofthe moving rays has been demonstrated. The formation of DS in LN with SPE by irradiation of coveredby electron resist polar surface of LN has been investigated. Formation of domains with arbitrary shapesas a result of discrete switching has been revealed. Finally, it has been demonstrated that electron beamirradiation of lithium niobate crystals with surface resist layer can produce high quality periodical domainpatterns after channel waveguide fabrication. Nonlinear characterizations show that the conversionefficiencies and the phase matching spectra conform to theoretical predictions, indicating that thiscombination presents a great interest for device fabrication. Second harmonic generation withnormalized nonlinear conversion efficiency up to 48%/(W cm2) has been achieved in such waveguides
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Wang, Yin-Yu. "Réseaux supraconducteurs : température critique et états mixtes." Grenoble 1, 1987. http://www.theses.fr/1987GRE10060.
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Les effets de quantification du flux magnetique sur des reseaux supraconducteurs bidimensionnels sont etudies dans ce memoire. Du point de vue theorique, la temperature de transition supraconductrice en fonction du champ magnetique applique est determinee en resolvant les equations d'alexander pour divers reseaux : periodiques, quasiperiodiques et fractals. Quelques un de ces reseaux submicroniques ont ete realises par lithographie electronique. Leurs temperatures critiques sont mesurees et l'accord entre la theorie et l'experience est discute. A l'interieur de la phase supraconductrice, les vortex entrent dans le reseau et induisent des supercourants diamagnetiques. L'etat d'equilibre est traite d'une maniere analogue au traitement de l'etat mixte d'un supraconducteur massif d'abrikosov : on determine l'amplitude du parametre d'ordre en tenant compte du terme non-lineaire de l'equation de ginzburg-landau par une methode de perturbation. On en deduit les quantites thermodynamiques, en particulier l'energie libre et l'aimantation du reseau, qui sont des fonctions de la difference entre la temperature et la temperature critique t - t::(c), ainsi que du parametre d'abrikosov beta ::(a). Ce formalisme a ete applique au reseau carre pour lequel les configurations du parametre d'ordre et les distributions du courant diamagnetique ont ete determinees pour quelques valeurs simples du champ magnetique. D'autre part, la derivee de la ligne critique par rapport au champ magnetique, qui s'identifie a la derivee du bord du spectre d'hofstadter a ete calculee a l'aide d'une approximation continue. Cette derivee contient un terme anormal que l'on peut relier a la phase de berry. Elle donne directement la derivee de l'aimantation par rapport a la temperature d rond m/d rond t. Nous donnons egalement quelques resultats preliminaires sur l'etat mixte du reseau supraconducteur en presence d'un courant exterieur. Le courant critique au-dessus duquel cet etat n'existe plus est obtenu pour quelques cas simples (boucles, reseau carre). Quelques mesures preliminaires de ce courant ont ete effectuees sur un reseau carre