Dissertations / Theses on the topic 'FIELD EMISSION OF ELECTRONS'
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1
Kuwahara, M., T. Morino, T. Nakanishi, S. Okumi, M. Yamamoto, M. Miyamoto, N. Yamamoto, et al. "Spin-Polarized Electrons Extracted from GaAs Tips using Field Emission." American Institite of Physics, 2007. http://hdl.handle.net/2237/11993.
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Sosa, Edward Delarosa. "The Electron Emission Characteristics of Aluminum, Molybdenum and Carbon Nanotubes Studied by Field Emission and Photoemission." Thesis, University of North Texas, 2002. https://digital.library.unt.edu/ark:/67531/metadc3311/.
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The electron emission characteristics of aluminum, molybdenum and carbon nanotubes were studied. The experiments were setup to study the emission behavior as a function of temperature and exposure to oxygen. Changes in the surface work function as a result of thermal annealing were monitored with low energy ultra-violet photoelectron spectroscopy for flat samples while field emission energy distributions were used on tip samples. The change in the field emission from fabricated single tips exposed to oxygen while in operation was measured using simultaneous Fowler-Nordheim plots and electron energy distributions. From the results a mechanism for the degradation in the emission was concluded. Thermal experiments on molybdenum and aluminum showed that these two materials can be reduced at elevated temperatures, while carbon nanotubes on the other hand show effects of oxidation. To purely reduce molybdenum a temperature in excess of 750 ºC is required. This temperature exceeds that allowed by current display device technology. Aluminum on the other hand shows reduction at a much lower temperature of at least 125 ºC; however, its extreme reactivity towards oxygen containing species produces re-oxidation. It is believed that this reduction is due to the outward diffusion of aluminum atoms through the oxide. Carbon nanotubes on the other hand show signs of oxidation as they are heated above 700 ºC. In this case the elevated temperatures cause the opening of the end caps allowing the uptake of water. Oxygen exposure experiments indicate that degradation in field emission is two-fold and is ultimately dependent on the emission current at which the tip is operated. At low emission currents the degradation is exclusively due to oxidation. At high emission currents ion bombardment results in the degradation of the emitter. In between the two extremes, molybdenum tips are capable of stable emission.
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Poa, Chun Hwa Patrick. "Electron field emission from carbons and their emission mechanism." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/842670/.
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This thesis is concerned with the research of the electron field emission properties of carbon based materials. Low emission threshold fields have been observed from both amorphous carbon thin films and carbon nanotubes. The emission mechanism can be subdivided into two groups depending on the type of electric field enhancement. These are the amorphous carbon flat films with non-geometric field enhancement and carbon nanotubes with high surface geometric field enhancement. Amorphous carbon thin films are deposited using an rf-plasma enhanced chemical vapour deposition technique. Changing the deposition conditions such as the addition of Argon or Nitrogen modifies the electronic properties. This induces variations in the sp2 concentration and its distribution within the films. The electron field emission properties from amorphous carbon thin films show a close relationship to its sp2 configuration. A model based on non-geometric field enhancement is proposed to explain the variation in the field emission characteristics. Nano-structured amorphous carbon films custom "designed" using ion beam assisted deposition with sp2 cluster sizes of around 60 nm have also been investigated. The field emission threshold field was shown to be controlled by the film's intrinsic stress and the local carbon density. With increasing stress, there is a concomitant increase in the local density, which is postulated to decrease the distance between the carbon graphitic "planes". This results in enhancement of the electron emission at lower fields. Stress within the films also induces changes to the band structure of the nano-structured carbon which are beneficial to the field emission process. Field emission from carbon nanotubes that are embedded in a polymer matrix has been investigated. The emission threshold fields are observed to be dependent on the nanotube density. The effect of electric field screening is used to explain the reduction of field enhancement observed in these films with increasing nanotube density. The field emission properties are compared with those films which have vertically aligned and in e-beam fabricated nanotube arrays. Results indicate that field emission properties from non-aligned nanotube films are comparable in performance to the best designed arrays in the literature. Although this study shows carbon based materials to have superior field emission properties, integrating the cathodes to fabricate commercial devices could prove to be very challenging.
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Collins, Clare Melissa. "Ordered nanomaterials for electron field emission." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270357.
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In the quest for reliable, repeatable and stable field electron emission that has commercial potential, whilst many attempts have been made, none yet has been truly distinguishable as being successful. Whilst I do not claim within this thesis to have uncovered the secret to success, fundamental issues have been addressed that concern the future directions towards achieving its full potential. An exhaustive comparison is made across the diverse range of materials that have, over the past 40-50 years, been postulated and indeed tested as field emitters. This has not previously been attempted. The materials are assessed according to the important metrics of turn on voltage, Eon, and maximum current density, Jmax, where low Eon and high Jmax are seen as desirable. The nano-carbons, carbon nanotubes (CNTs), in particular, perform well in both these metrics. No dependency was seen between the material work function and its performance as an emitter, which might have been suggested by the Fowler Nordheim equations. To address the issues underlying the definition of the local enhancement factor, β, a number of variations of surface geometry using CNTs were fabricated. The field emission of these emitters was measured using two different approaches. The first is a Scanning Electrode Field Emission Microscope, SAFEM, which maps the emission at individual locations across the surface of the emitter, and the parallel plate that is more commonly encountered in field emission measurements. Finally, an observed hysteretic behaviour in CNT field emission was explored. The field emitters were subjected to a number of tests. These included; in-situ residual gas analysis of the gas species in the emitter environment, a stability study in which the emitters were exposed to a continuing voltage loop for 50 cycles, differing applied voltage times to analyse the effects on the emitted current, and varying maximums of applied field in a search for hysteresis onset information. These studies revealed the candidate in causing the hysteresis is likely to be water vapour that adsorbs on the CNT surface. A six step model if the emission process was made that details how and when the hysteresis is caused.
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Kuhnen, Raphael [Verfasser], and Bernd von [Akademischer Betreuer] Issendorf. "Electron wave packet interference and directed emission of electrons in a two color laser field = Elektronenwellenpacketinterferenz und gerichtete Emission von Elektronen in einem zweifarben Laserfeld." Freiburg : Universität, 2012. http://d-nb.info/1123467781/34.
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Laou, Philips. "Field emission devices on silicon." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/NQ44486.pdf.
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Tsang, Wei Mong. "Electron field emission properties from nanoengineered structures." Thesis, University of Surrey, 2006. http://epubs.surrey.ac.uk/844374/.
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This work is mainly divided into three parts. Firstly, with the aim of integrating electron field emitter with other circuit elements on a single chip, silver-silicon dioxide (Ag-SiO2) nanocomposites are fabricated and studied. The Ag-SiO2 nanocomposites are synthesised by Ag implantation into thermally oxidised SiO2 layers on Si substrates and their fabrication processes are fully compatible with existing integrated circuit technology and their threshold fields are less than 20 V/mum. The local field enhancement mechanisms were studied and the fabrication processes of these layers optimised. Secondly, the electron field emission (FE) properties of two-dimensional quantum confinement structure were studied. Band gap modulated amorphous carbon (alpha-C) nanolayers were synthesised by pulsed laser deposition. In these structures, electrons are confined in a few nm thick low band gap sp2 rich alpha-C layer, which is bound by the vacuum barrier and a 3 nm thick high band gap sp3 rich alpha-C base layer. Anomalous FE properties, including negative differential conductance and repeatable switching effects, are observed when compared to control samples. These properties will be discussed in terms of resonant tunnelling and are of great interest in the high-speed vacuum microelectronic devices. Finally, due to the interesting electrical transport properties and rare FE characteristics of metal quantum dots (QDs), cobalt QDs were synthesized in a SiO2 matrix by ion implantation. Staircase-like current-field characteristics were observed for the first time from these samples and give an experimental insight into existing Coulomb Blockade effects in the metal QDs during the FE process. Moreover, these samples also achieve excellent FE properties with threshold fields less than 5 V/mum and are comparable with other popular FE materials.
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Tang, Yew Fei. "Electron field emission from laser crystallised amorphous silicon." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/843179/.
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Flat panel displays based on electron field emission can provide the benefits of the high resolution of a cathode ray tube display while possessing the portability of a liquid crystal display. To date, the problem with a field emission flat panel display based on silicon is that it usually involves complex photolithography processing, making it too complex and expensive to be commercially viable. In this thesis, the emphasis of the research is to fabricate a three terminal silicon device for flat panel display based on field emission technology without using photolithography processes. Laser crystallised amorphous silicon is chosen for our material which creates a rough silicon surface whose roughness gives rise to field enhancement. Furthermore, this process is widely used in the display industry to fabricate silicon based display driver thin film transistors, which can be readily incorporated. It is important to understand the electron field emission mechanism from the laser crystallised amorphous silicon and to find optimum conditions for emission. In the course of our research, we established a regime for super sequential lateral growth or a hybrid sequential lateral solidification and super lateral growth in Nd:YAG crystallisation of amorphous silicon. Excimer laser crystallised amorphous silicon under optimum conditions gives emission currents of the order of 10-5A (current densities ~ 0.04 A/cm2) at threshold fields less than 15 V/mum in a diode configuration, without the need for a forming process. Through experiments, we concluded that the field emission mechanism from these samples is not controlled purely by surface phenomena, contrary to what was suggested by the Fowler Nordheim theory. Instead, it is the diffusion of the underlay metals into the silicon that create clusters of silicide that allow the electrons to become "hot" while travelling between the clusters. Lastly, a novel process illustrating that a three-terminal device based on laser crystallised amorphous silicon can be fabricated without the need for photolithography. However, the field emission data showed that some fine-tuning of the process is still required.
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Smith, Richard Charles. "Electron field emission properties of tip based emitters." Thesis, University of Surrey, 2005. http://epubs.surrey.ac.uk/843091/.
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Large area displays such as laptop computers and flat screen televisions have enormous market potential. There are numerous technologies in existence today, including LCD (liquid crystal displays) and plasma, however they each suffer from unique limitations, mainly the size of the display and operating conditions. There is still a need for a method of depositing electronic materials over large areas at suitable temperatures. This is important since the construction of panels using sub-modules such as crystalline silicon wafers is very difficult and expensive. The displays based on liquid crystals that use thin film transistor (TFT) driven active matrix addressing is the most common flat screen technology at present. However, there are great problems associated with yield in fabrication, especially for screen dimensions over 14 inches. Hence the screens are very expensive. Field emission displays utilising the phenomenon of field emission in which electrons escape their work function and "jump" from the surface of the semiconductor into a vacuum has been proposed as a competing technology. Each pixel is controlled by many tip based emitters, therefore improving the yield. This thesis explores the field emission properties and mechanisms of tip based emitters, and also explore the possibility of utilising carbon nanotubes as electron sources for field emission displays.
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Forrest, Roy Duncan. "Electron field emission from amorphous semiconductor thin films." Thesis, University of Surrey, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484237.
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Ptitsin, V. E. "New Thermal Field Electron Emission Energy Conversion Method." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35247.
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New thermal field electron emission energy conversion method for vacuum electron-optical systems
(EOS) with a nanostructured surface electron sources is offered and developed. Physical and numerical
modeling of an electron emission and transport processes for different EOS is carried out. It is shown that
at the specific configuration of electrostatic and magnetic fields in the EOS offered method permits to
realize energy conversion processes with high efficiency.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35247
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Parmee, Richard. "X-ray generation by field emission." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/284924.
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Since the discovery of X-rays over a century ago the techniques applied to the engineering of X-ray sources have remained relatively unchanged. From the inception of thermionic electron sources, which, due to simplicity of fabrication, remain central to almost all X-ray applications at this time, there have been few fundamental technological advances. The emergence of new materials and manufacturing techniques has created an opportunity to replace the traditional thermionic devices with those that incorporate Field Emission electron sources. One of the most important attributes of Field Emission X-ray sources is their controllability, and in particular the fast response time, which opens the door to applying techniques which have formerly been the preserve of optical systems. The work in this thesis attempts to bridge the gap between the fabrication and optimisation of the vacuum electronic devices and image processing aspects of a new approach to high speed radiographic imaging, particularly with a view to addressing practical real-world problems. Off the back of a specific targeted application, the project has involved the design of a viable field emission X-ray source, together with the development of an understanding of the failure modes in such devices, both by analysis and by simulation. This thesis reviews the capabilities and the requirements of X-ray sources, the methods by which nano-materials may be applied to the design of those devices and the improvements and attributes that can be foreseen. I study the image processing methods that can exploit these attributes, and investigate the performance of X-ray sources based upon electron emitters using carbon nanotubes. Modelling of the field emission and electron trajectories of the cathode assemblies has led me to the design of equipment to evaluate and optimise the parameters of an X-ray tube, which I have used to understand the performance that is achievable. Finally, I draw conclusions from this work and outline the next steps to provide the basis for a commercial solution.
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Tirolli, Marcelo Nogueira. "Modelamento computacional de ponteiras de emissão de campo." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259568.
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Orientador: Marco Antonio Robert AlvesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-09T17:44:13Z (GMT). No. of bitstreams: 1 Tirolli_MarceloNogueira_M.pdf: 2758197 bytes, checksum: 08f6e633be3e083c0e72c41959dd296d (MD5) Previous issue date: 2007
Resumo: Este trabalho tem como objetivo o estudo do comportamento elétrico de uma ponteira de emissão de campo, modelada na forma de um hemisfério sobre um poste, através de recursos computacionais (simulações). Escolhemos o software comercial Ansys, que utiliza o método dos elementos finitos nas análises dos fenômenos físicos para obtenção do campo elétrico na superfície da ponteira. Em seguida, foi desenvolvido também um programa computacional que realiza o cálculo da corrente de emissão baseado na teoria de emissão de campo de Fowler-Nordheim (F-N). Para calcular a corrente, o programa faz uso dos resultados das simulações do campo elétrico obtidos no software Ansys. Apresentamos também os resultados da influência que as dimensões como o raio de curvatura do hemisfério, a altura da ponteira e a distância entre anodo e catodo exercem sobre o comportamento do campo elétrico, da corrente de emissão e de outras grandezas físicas que envolvem emissão de campo
Abstract: This work aims to study the electrical behavior of a field emission tip, shaped in the form hemisphere on a post, through computational resources (simulations). We chose the Ansys commercial software that uses the finite element methods in the analyses of the physical phenomena to obtain the electric field in the surface of the tip. After that, a computational program was also developed to perform the calculation of emission current based on Fowler-Nordheim (F-N) field emission theory. To calculate the current, the program uses the results of the electric field simulations gotten in Ansys software. We also show the results of influences that dimensions such as the hemisphere curvature radius, the height of the tip and the distance between anode and cathode exert on the behavior of the electric field, emission current and other physical quantities that involve field emission
Mestrado
Eletrônica, Microeletrônica e Optoeletrônica
Mestre em Engenharia Elétrica
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Sanchez, Jaime A. "ELECTRON FIELD-EMISSION FROM CARBON NANOTUBES FOR NANOMACHINING APPLICATIONS." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/590.
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The ability to pattern in the nanoscale to drill holes, to draw lines, to make circles, or more complicated shapes that span a few atoms in width is the main driver behind current efforts in the rapidly growing area of nanomanufacturing. In applications ranging from the microprocessor industry to biomedical science, there is a constant need to develop new tools and processes that enable the shrinking of devices. For this and more applications, nanomanufacturing using electron beams offers a window of opportunity as a top-down approach since electrons, unlike light, have a wavelength that is in the order of the atomic distance. Though the technology based on electron beams has been available for more than twenty years, new concepts are constantly being explored and developed based on fundamental approaches. As such, a tool that utilizes electron field-emission from carbon nanotubes was proposed to accomplish such feats. A full numerical analysis of electron field-emission from carbon nanotubes for nanomachining applications is presented. The different aspects that govern the process of electron field-emission from carbon nanotubes using the finite element method are analyzed. Extensive modeling is carried here to determine what the effect of different carbon nanotube geometries have on their emission profiles, what energy transport processes they are subject to, and establish what the potential experimental parameters are for nanomachining. This dissertation builds on previous efforts based on Monte Carlo simulations to determine electron deposition profiles inside metals, but takes them to next level by considering realistic emission scenarios. A hybrid numerical approach is used that combines the two-temperature model with Molecular Dynamics to study phase change and material removal in depth. The use of this method, allows the determination of the relationship between the amount of energy required to remove a given number of atoms from a metallic workpiece and the number of carbon nanotubes and their required settings in order to achieve nanomachining. Finally, the grounds for future work in this area are provided, including the need for novel electron focusing systems, as well as the extension of the hybrid numerical approach to study different materials.
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Wang, Tong. "Enhanced Field Emission Studies on Nioboim Surfaces Relevant to High Field Superconducting Radio-Frequency Devices." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/29284.
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Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling.
The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE.
To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance.
EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m.
To address concerns on the effect of natural air drying process on EFE, a comparative study was conducted on Nb and the results showed insignificant difference under the experimental conditions.
Nb thin films deposited on Cu present a possible alternative to bulk Nb in superconducting cavities. The EFE performance of a preliminary energetically deposited Nb thin film sample are presented.Ph. D.
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Archer, Anthony D. "Spectroscopic studies of field-induced electron emission from isolated microstructures." Thesis, Aston University, 1992. http://publications.aston.ac.uk/8241/.
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A detailed investigation has been undertaken into the field induced electron emission (FIEE) mechanism that occurs at microscopically localised `sites' on uncoated and dielectric coated metallic electrodes. These processes have been investigated using two dedicated experimental systems that were developed for this study. The first is a novel combined photo/field emission microscope, which employs a UV source to stimulate photo-electrons from the sample surface in order to generate a topographical image. This system utilises an electrostatic lens column to provide identical optical properties under the different operating conditions required for purely topographical and combined photo/field imaging. The system has been demonstrated to have a resolution approaching 1m. Emission images have been obtained from carbon emission sites using this system to reveal that emission may occur from the edge triple junction or from the bulk of the carbon particle. An existing UHV electron spectrometer has been extensively rebuilt to incorporate a computer control and data acquisition system, improved sample handling and manipulation and a specimen heating stage. Details are given of a comprehensive study into the effects of sample heating on the emission process under conditions of both bulk and transient heating. Similar studies were also performed under conditions of both zero and high applied field. These show that the properties of emission sites are strongly temperature and field dependent thus indicating that the emission process is `non-metallic' in nature. The results have been shown to be consistent with an existing hot electron emission model.
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Andrew), Patterson Alex A. (Alex. "Theory and modeling of field electron emission from low-dimensional electron systems." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115640.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 253-271).
While experimentalists have succeeded in fabricating nanoscale field electron emitters in a variety of geometries and materials for use as electron sources in vacuum nanoelectronic devices, theory and modeling of field electron emission have not kept pace. Treatments of field emission which address individual deviations of real emitter properties from conventional Fowler-Nordheim (FN) theory, such as emission from semiconductors, highly-curved surfaces, or low-dimensional systems, have been developed, but none have sought to treat these properties coherently within a single framework. As a result, the work in this thesis develops a multidimensional, semiclassical framework for field emission, from which models for field emitters of any dimensionality, geometry, and material can be derived. The effects of quantum confinement and emitter tip geometry on the properties of emission were investigated by utilizing the framework to derive models for: i) a highly-curved, nanoscale, metal emitter tip; ii) a bulk silicon emitter with a surface quantum well formed due to electric field penetration and a mechanism that limits the maximum conduction band emitted current density (ECD) to the bulk flux density supply; and iii) a cylindrical silicon nanowire emitter. Results from a highly-curved, nanoscale, metal emitter tip reveal that despite signicant electron supply reductions as a result of quantum confinement, the emitted current density (ECD) increases as the emitter radius decreases due to the effects of electric field enhancement. Additionally, emitters with radii smaller than 5 nm exhibit a narrow total energy distribution and highly non-linear FN plots. Consistent with experimental observations, the saturation of the conduction band ECD in silicon emitters leads to the appearance of three distinct regions in FN plots, which signify conduction-band-dominated, valence-band-dominated, and transitional regimes of emission. Confinement of electrons to a nanowire emitter geometry further reduces the electron supply available for emission and, consequently, the conduction band saturation ECD. Overall, findings show that the dimensionality, geometry, and material of field emitters all play a critical role in field emission processes at the nanoscale. Accordingly, the semiclassical framework for field emission is intended to form a solid foundation upon which more complete models of emission can be developed.
by Alex Andrew Patterson.
Ph. D.
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Day, Christopher M. "Field enhanced thermionic emission from oxide coated carbon nanotubes." Virtual Press, 2006. http://liblink.bsu.edu/uhtbin/catkey/1348860.
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A cathode structure was demonstrated that utilizes aligned carbon nanotubes (CNTs) to improve the thermionic electron emission by increasing the field enhancement of the cathode surface. Aligned CNTs were grown on the surface of a tungsten substrate by plasma enhanced chemical vapor deposition. The tungsten-CNT structure was further coated with a thin film of low work function emissive materials by magnetron sputtering. Numerous cathodes with varying CNT morphology and oxide layer thickness were created. The field and thermionic emission of the cathodes were tested in order to study the effects of the surface properties on the emission characteristics. It was observed that the introduction of CNTs into an oxide cathode structure improves both the thermionic and field emission, even in cathodes with relatively low field enhancement factors. Because of the high field enhancement factors that are available for CNTs, there remains a potential for dramatically improved electron emission.Department of Physics and Astronomy
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Sanborn, Graham Patrick. "A thin film triode type carbon nanotube field electron emission cathode." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50302.
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The current technological age is embodied by a constant push for increased performance and efficiency of electronic devices. This push is particularly observable for technologies that comprise free electron sources, which are used in various technologies including electronic displays, x-ray sources, telecommunication equipment, and spacecraft propulsion. Performance of these systems can be increased by reducing weight and power consumption, but is often limited by a bulky electron source with a high energy demand.
Carbon nanotubes (CNTs) show favorable properties for field electron emission (FE) and performance as electron sources. This dissertation details the developments of a uniquely designed Spindt type CNT field emission array (CFEA), from initial concept to working prototype, to specifically prevent electrical shorting of the gate. The CFEA is patent pending in the United States. Process development enabled fabrication of a CFEA with a yield of up to 82%. Furthermore, a novel oxygen plasma etch process was developed to reverse shorting after CNT synthesis. CFEA testing demonstrates FE with a current density of up to 293 μA/cm² at the anode and 1.68 mA/cm² at the gate, with lifetimes in excess of 100 hours. A detailed analysis of eighty tested CFEAs revealed three distinct types of damage. Surprisingly, about half of the damaged chips are not electrically shorted, indicating that the CFEAs are very robust.
Potential applications of this technology as cathodes for spacecraft electric propulsion were explored. Exposure to an operating electric propulsion thruster showed no significant effect or damage to the CFEAs, marking the first experimental study of CNT field emitters in an electric propulsion environment. A second effort in spacecraft propulsion is a collaboration with the Air Force Institute of Technology (AFIT). CFEAs are the payload on an AFIT developed Cube Satellite, called ALICE, to test electron emission in the space environment. ALICE has passed flight tests and is awaiting launch scheduled for 5 December 2013.
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Andrew), Patterson Alex A. (Alex. "An analytical framework for field electron emission, incorporating quantum- confinement effects." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84863.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 141-151).
As field electron emitters shrink to nanoscale dimensions, the effects of quantum confinement of the electron supply and electric field enhancement at the emitter tip play a significant role in determining the emitted current density (ECD). Consequently, the Fowler-Nordheim (FN) equation, which primarily applies to field emission from the planar surface of a bulk metal may not be valid for nanoscale emitters. While much effort has focused on studying emitter tip electrostatics, not much attention has been paid to the consequences of a quantum-confined electron supply. This work builds an analytical framework from which ECD equations for quantum-confined emitters of various geometries and materials can be generated and the effects of quantum confinement of the electron supply on the ECD can be studied. ECD equations were derived for metal emitters from the elementary model and for silicon emitters via a more physically-complete version of the elementary model. In the absence of field enhancement at the emitter tip, decreasing an emitter's dimensions is found to decrease the total ECD. When the effects of field enhancement are incorporated, the ECD increases with decreasing transverse emitter dimensions until a critical dimension dpeak, below which the reduced electron supply becomes the limiting factor for emission and the ECD decreases. Based on the forms of the ECD equations, alternate analytical methods to Fowler-Nordheim plots are introduced for parameter extraction from experimental field emission data. Analysis shows that the FN equation and standard analysis procedures over-predict the ECD from quantum-confined emitters. As a result, the ECD equations and methods introduced in this thesis are intended to replace the Fowler-Nordheim equation and related analysis procedures when treating field emission from suitably small field electron emitters.
by Alex A. Patterson.
S.M.
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Xu, Ningsheng. "Field induced hot electron emission from composite metal-insulator-metal microstructures." Thesis, Aston University, 1986. http://publications.aston.ac.uk/8048/.
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Little, Scott A. "Experimental and numerical studies of a new thermionic emitter structure based on oxide coated carbon nanotubes operating at large emission currents." Virtual Press, 2007. http://liblink.bsu.edu/uhtbin/catkey/1380104.
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We have developed a thermionic cathode capable of high emission currents. The structure of this cathode is oxide coated carbon nanotubes (CNTs) on a tungsten (W) substrate. This cathode was superior in emission due to the combination of the field enhancement effect from the CNTs and the lowered work function from the semiconducting oxide surface. Such oxide coated CNTs were excellent electron emitters. Conventional electron emission theories, such as Richardson's and Fowler-Nordheim's, did not accurately describe the field enhanced thermionic emission from such emitters. A unified electron emission theory was adopted and numerical simulations were performed to explain the deviation of electron emission from conventional field and thermionic emission theories. Also, the thermionic measurement system and measurement methods were improved in order to measure and characterize the strong electron emission from this new cathode. Large electron emission current from such structures also made a new thermionic cooling device a possibility. Cooling due to the electron emission was measured in terms of temperature drop, and a large temperature drop was observed from this cathode structure. Finally, applications of this cathode in plasma discharge devices were explored. This new cathode was tested in a plasma environment and initial results were obtained.Department of Physics and Astronomy
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Carr, Christopher G. "Space charge-limited emission studies using Coulomb's Law." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FCarr.pdf.
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Walton, Jonathan Seabrooke. "Analysis of surface treated chemical vapour deposited diamond for field electron emission." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/520.
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Kudjoe, John. "Design and development of field emission electron columns with variable beam energy." Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259834.
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Che, Yulu. "Ambipolar Ballistic Electron Emission Microscopy Studies of Gate-field Modified Schottky Barriers." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1282070943.
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Pasquetto, Mariana Pinheiro. "Estudo do fenomeno de emissão de eletrons por campo eletrico em nanotubos de carbono." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259945.
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Orientador: Vitor BaranauskasDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Materiais emissores de elétrons são extremamente importantes no ramo da micro e nano eletrônica, como por exemplo, em displays, microscópios eletrônicos, sensores de pressão. Para essas aplicações, podem ser usados catodos frios, ou seja, materiais que não necessitam ser aquecidos para emitirem elétrons. Através da aplicação de um campo elétrico local, aumenta-se a probabilidade dos elétrons tunelarem do sólido para o vácuo. Este é o fenômeno de emissão de campo. Essa dissertação apresenta os resultados da emissão de elétrons por efeito de campo elétrico (emissão de campo) de amostras de nanotubos de carbono, dopados e não-dopados com boro e nitrogênio. As amostras estudadas foram fornecidas pelo Laboratório de NanoEngenharia I do DSIF, FEEC. É feita, também, uma descrição da teoria de emissão de campo e de algumas aplicações desse fenômeno. Verificou-se que os materiais testados são bons emissores de elétrons.
Abstract: Electron emitter materials are extremely important in the field of micro and nano electronics, for example, in displays, electronic microscopes, pressure sensors. For such applications, cold cathodes can be used, that is, materials that do not need to be heated to emit electrons. Through the application of a local electric field, it is increased the probability of the electrons to tunnel from the solid. This is the phenomenon of field emission. This dissertation presents the results of the electron emission in the presence of an electric field (field emission) of samples of carbon nanotubes, undoped and doped with boron and nitrogen. The samples were provided by the Laboratório de NanoEngenharia I from DSIF, FEEC. It is also made a description of the field emission theory and of some applications of this phenomenon. It was found that the materials tested are good electron emitters.
Mestrado
Eletrônica, Microeletrônica e Optoeletrônica
Mestre em Engenharia Elétrica
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Neuerman, Robert A. "Simulation and design methods for free-electron laser systems." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FNeuerman.pdf.
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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2009.Thesis Advisor(s): Colson, William B. ; Blau, Joseph. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: Free-electron lasers, FEL simulations, undulators, FEL oscillators, FEL amplifiers, diamond field-emitter arrays, field emission cathodes, cathode test cell. Includes bibliographical references (p. 45). Also available in print.
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Seelaboyina, Raghunandan. "Robust and High Current Cold Electron Source Based on Carbon Nanotube Field Emitters and Electron Multiplier Microchannel Plate." FIU Digital Commons, 2007. http://digitalcommons.fiu.edu/etd/217.
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The aim of this research was to demonstrate a high current and stable field emission (FE) source based on carbon nanotubes (CNTs) and electron multiplier microchannel plate (MCP) and design efficient field emitters. In recent years various CNT based FE devices have been demonstrated including field emission displays, x-ray source and many more. However to use CNTs as source in high powered microwave (HPM) devices higher and stable current in the range of few milli-amperes to amperes is required. To achieve such high current we developed a novel technique of introducing a MCP between CNT cathode and anode. MCP is an array of electron multipliers; it operates by avalanche multiplication of secondary electrons, which are generated when electrons strike channel walls of MCP. FE current from CNTs is enhanced due to avalanche multiplication of secondary electrons and in addition MCP also protects CNTs from irreversible damage during vacuum arcing. Conventional MCP is not suitable for this purpose due to the lower secondary emission properties of their materials. To achieve higher and stable currents we have designed and fabricated a unique ceramic MCP consisting of high SEY materials. The MCP was fabricated utilizing optimum design parameters, which include channel dimensions and material properties obtained from charged particle optics (CPO) simulation. Child Langmuir law, which gives the optimum current density from an electron source, was taken into account during the system design and experiments. Each MCP channel consisted of MgO coated CNTs which was chosen from various material systems due to its very high SEY. With MCP inserted between CNT cathode and anode stable and higher emission current was achieved. It was ~25 times higher than without MCP. A brighter emission image was also evidenced due to enhanced emission current. The obtained results are a significant technological advance and this research holds promise for electron source in new generation lightweight, efficient and compact microwave devices for telecommunications in satellites or space applications. As part of this work novel emitters consisting of multistage geometry with improved FE properties were was also developed.
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Knoop, Ludvig de. "Development of quantitative in situ transmission electron microscopy for nanoindentation and cold-field emission." Toulouse 3, 2014. http://thesesups.ups-tlse.fr/3041/.
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Cette thèse porte sur le développement d'analyse quantitative d'expérience in situ de microscopie électronique en transmission (MET). Nous avons utilisé un porte objet spécial, qui combine les fonctions de polarisation électrique locale et tests de micro-mécanique. La méthode des éléments finis (MEF) a été mise en œuvre afin de comparer les résultats issus de la modélisation avec les résultats expérimentaux. En plus des techniques d'imagerie classique, l'holographie électronique a été employée pour mesurer des champs électriques et de déformation. La première partie traite de l'émission de champ d'une nanopointe faite d'un cône de carbone (CCnT). Ce nouveau type de matériaux pourrait remplacer les pointes de tungstène qui sont utilisés dans les canons d'électrons les plus avancés. Quand un champ électrique suffisamment fort est appliqué au CCnT, les électrons peuvent passer à travers la barrière d'énergie avec le vide par effet tunnel, ce qui correspond au phénomène d'émission de champ. En combinant holographie électronique avec les simulations MEF, une valeur quantitative du champ électrique local a été obtenue pour l'émission (2,5 V/nm). En faisant appel aux équations de Fowler-Nordheim, une valeur de la fonction de travail de sortie du CCnT est déterminée (4,8±0,3 eV). Nous avons également mesuré les charges sur le CCnT, avant et après le début de l'émission de champ. La deuxième partie porte sur la déformation plastique d'un film mince d'Al pour tester les interactions des dislocation - interface. Une dislocation à proximité d'une interface avec un matériau plus rigide doit être repoussée par celle-ci. Ici, nous constatons que les dislocations qui vont vers l'interface oxydée sont absorbées par cette interface rigide, même à température ambiante. La contrainte locale est déterminée par une combinaison de mesures de forces par le capteur et de calculs MEF. Enfin, des résultats préliminaires de combiner indentation in situ et holographie électronique en champ sombre sont présentésThis thesis has focused on the development of quantitative in situ transmission electron microscopy (TEM) techniques. We have used a special nano-probe sample holder, which allows local electrical biasing and micro-mechanical testing. The finite element method (FEM) was used to compare models with the experimental results. In addition to conventional imaging techniques, electron holography has been used to measure electric fields and strains. The first part addresses cold-field emission from a carbon cone nanotip (CCnT). This novel type of carbon structure may present an alternative to W-based cold-field emission sources, which are used in the most advanced electron guns today. When a sufficiently strong electric field is applied to the CCnT, electrons can tunnel through the energy barrier with the vacuum, which corresponds to the phenomenon of cold-field emission. Using electron holography and FEM, a quantified value of the local electric field at the onset of field emission was found (2. 5 V/nm). Combining this with one of the Fowler-Nordheim equations, the exit work function of the CCnT was determined to be 4. 8±0. 3 eV. The number of charges on the CCnT before and after the onset of field emission was also measured. The second part focuses on the plastic deformation of Al thin films to test dislocation-interface interactions. A dislocation close to an interface with a stiffer material should be repelled by it. Here, we find to the contrary that dislocations moving towards the oxidized interface are absorbed, even at room temperature. The stress was derived from a combination of load-cell measurements and FEM calculations. Finally, preliminary experiments to combine in situ indentation and dark-field electron holography are reported
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Chen, Li. "Fabrication of electron sources for a miniature scanning electron microscope." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313904.
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Singh, Gopal [Verfasser]. "Development and characterization of a LaB6 based high brightness field emission electron source / Gopal Singh." Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2020. http://nbn-resolving.de/urn:nbn:de:gbv:18-ediss-88773.
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Christy, Larry A. "Field Emission Properties of Carbon Nanotube Fibers and Sheets for a High Current Electron Source." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406819279.
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Lagotzky, Stefan, Roman Barday, Andreas Jankowiak, Thorsten Kamps, Carola Klimm, Jens Knobloch, Günter Müller, Boris Senkovsky, and Frank Siewert. "Prevention of electron field emission from molybdenum substrates for photocathodes by the native oxide layer." Cambridge University Press, 2015. https://tud.qucosa.de/id/qucosa%3A39022.
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Comprehensive investigations of the electron field emission (FE) properties of annealed single crystal and polycrystalline molybdenum plugs, which are used as substrates for actual alkali-based photocathodes were performed with a FE scanning microscope. Well-polished and dry-ice cleaned Mo samples with native oxide did not show parasitic FE up to a field level of 50 MV/m required for photoinjector cavities. In situ heat treatments (HT) above 400°C, which are usual before photocathode deposition, activated field emission at lower field strength. Oxygen loading into the Mo surface, however, partially weakened these emitters. X-ray photoelectron spectroscopy of comparable Mo samples showed the dissolution of the native oxide during such heat treatments. These results reveal the suppression of field emission by native Mo oxides. Possible improvements for the photocathode preparation will be discussed.
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West, Ryan Matthew. "Work function fluctuation analysis of polyaniline films." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47586.
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In this thesis, the development of a novel experimental technique for measuring the spontaneous, stochastic work function (WF) fluctuations of conducting polymer films, at equilibrium, is discussed. Polyaniline (PANI) is studied as a representative conducting polymer. This technique utilizes an insulated-gate field-effect transistor (IGFET) with PANI gate electrode (PANI-IGFET). The fluctuations of PANI WF are transduced into measurable drain current fluctuations of the device. By analyzing these fluctuations while systematically controlling the temperature, electric field and doping level, a model of WF fluctuations in PANI films is developed. These experiments suggest that the source of WF fluctuations is the hopping of charge carriers, or trapping/detrapping of charge carriers, around the Fermi level of the PANI film at the PANI-insulator interface. This process is thermally activated with a field and doping dependent activation energy in the range of 0.1 to 0.5 eV. Thus, this new technique provides detailed information about charge-carrier dynamics in the space-charge region of the PANI film, at equilibrium. These results have important implications for organic electronics and furthering fundamental understanding of the relationship between doping, disorder and work function in organic semiconductors.
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Neupane, Suman. "Synthesis and Electron Emission Properties of Aligned Carbon Nanotube Arrays." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1168.
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Carbon nanotubes (CNTs) have become one of the most interesting allotropes of carbon due to their intriguing mechanical, electrical, thermal and optical properties. The synthesis and electron emission properties of CNT arrays have been investigated in this work. Vertically aligned CNTs of different densities were synthesized on copper substrate with catalyst dots patterned by nanosphere lithography. The CNTs synthesized with catalyst dots patterned by spheres of 500 nm diameter exhibited the best electron emission properties with the lowest turn-on/threshold electric fields and the highest field enhancement factor. Furthermore, CNTs were treated with NH3 plasma for various durations and the optimum enhancement was obtained for a plasma treatment of 1.0 min. CNT point emitters were also synthesized on a flat-tip or a sharp-tip to understand the effect of emitter geometry on the electron emission. The experimental results show that electron emission can be enhanced by decreasing the screening effect of the electric field by neighboring CNTs.
In another part of the dissertation, vertically aligned CNTs were synthesized on stainless steel (SS) substrates with and without chemical etching or catalyst deposition. The density and length of CNTs were determined by synthesis time. For a prolonged growth time, the catalyst activity terminated and the plasma started etching CNTs destructively. CNTs with uniform diameter and length were synthesized on SS substrates subjected to chemical etching for a period of 40 minutes before the growth. The direct contact of CNTs with stainless steel allowed for the better field emission performance of CNTs synthesized on pristine SS as compared to the CNTs synthesized on Ni/Cr coated SS.
Finally, fabrication of large arrays of free-standing vertically aligned CNT/SnO2 core-shell structures was explored by using a simple wet-chemical route. The structure of the SnO2 nanoparticles was studied by X-ray diffraction and electron microscopy. Transmission electron microscopy reveals that a uniform layer of SnO2 is conformally coated on every tapered CNT. The strong adhesion of CNTs with SS guaranteed the formation of the core-shell structures of CNTs with SnO2 or other metal oxides, which are expected to have applications in chemical sensors and lithium ion batteries.
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Liška, Ivo. "Coulomb Interactions in Electron Beams in the Vicinity of a Schottky and Cold Field Emission Sources." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233896.
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Dizertační práce se zabývá problematikou výpočtu vlivu coulombovských interakcí částic na parametry emitovaného elektronového svazku v blízkosti Schottkyho a studené katody. Práce poskytuje základní předhled o problematice, popisuje vytvořené modely emisních zdrojů a metodu simulace Monte Carlo. Představuje novou metodu generování vstupních dat, která klade větší důraz na přesnou simulaci emisního procesu. Pozornost je zde věnována zejména vlivu interakcí na energiovou šířku, velikost virtuálního zdroje a jas katody v závislosti na velikosti poloměru hrotu a emisním proudu. Sledováním vývoje energiové šířky bylo zjištěno, že naprostá většina interakcí se odehrává v prostoru do několika mikrometrů od hrotu katody. Závislost spočtené celkové energiové šířky na úhlové intenzitě je ve shodě s dostupnými experimentálními daty. Spočtené energiové rozšíření vlivem coulombovských interakcí bylo srovnáno s hodnotami vypočtenými pomocí vzorců založených na analytických přiblíženích. Bylo zjištěno, že některé z nich přijatelně předpovídají trendy ale nemohou být použity pro kvantitativní odhad.
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Hii, King-Fu. "A PRECISION INSTRUMENT FOR RESEARCH INTO NANOLITHOGRAPHIC TECHNIQUES USING FIELD-EMITTED ELECTRON BEAMS." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/675.
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Nanomanufacturing is an active research area in academia and industry due to the ever-growing demands for precision surface modifications of thin films or substrates with nanoscale features. Conventional lithographic techniques face many challenges as they approach their fundamental limits. Consequently, new nanomanufacturing tools, fabrication techniques, and precision instruments are being explored and developed to meet these challenges. It has been hypothesized that direct-write nanolithography might be achieved by using a field-emitted electron beam for nanomachining. This dissertation moves this research one step closer by developing a precision instrument that can enable the integration of direct-write nanolithography by a field-emitted electron beam with dimensional metrology by scanning tunneling microscopy. First, field emission from two prospective electron sources, a carbon nanotube field emitter and a sharp tungsten field emitter, is characterized at distances ranging from sub-micrometer to a few micrometers. Also, the design and construction of a low thermal drift piezoelectric linear motor is described for tip-sample approach. Experiments indicate that: the step size is highly repeatable with a standard deviation of less than 1.2 nm and the thermal stability is better than 40 nm/◦C. Finally, the design and construction of the instrument are presented. Experiments indicate that: the instrument is operating properly in scanning tunneling microscope mode with a resolution of less than 2 Å.
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Takamura, S., S. Mizoshita, and N. Ohno. "Suppression of secondary electron emission from the material surfaces with grazing incident magnetic field in the plasma." American Institute of Physics, 1996. http://hdl.handle.net/2237/6993.
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"Field emission properties of a silicon tip array." 2001. http://library.cuhk.edu.hk/record=b5890592.
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Fung Yun Ming.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.
Includes bibliographical references (leaves 134-140).
Abstracts in English and Chinese.
Abstract --- p.I
Acknowledgement --- p.III
Contents --- p.IV
List of Figure captions --- p.VIII
List of Table captions --- p.XIII
Chapter Chapter 1 --- Introduction --- p.1
Chapter Chapter 2 --- Theory and Applications
Chapter 2.1 --- Principle of field emission
Chapter 2.1.1 --- The Fowler-Nordheim Theory --- p.3
Chapter 2.1.2 --- Field emission from metals --- p.6
Chapter 2.1.3 --- Field emission from semiconductors --- p.8
Chapter 2.1.3.1 --- Advantages and limitations of silicon --- p.9
Chapter 2.1.4 --- Application of the Fowler-Nordheim theory --- p.10
Chapter 2.1.5 --- Factors influencing field emission efficiency --- p.11
Chapter 2.2 --- Applications --- p.11
Chapter 2.2.1 --- Operation of a Field Emission Displays --- p.11
Chapter 2.2.2 --- Basic structure of a Field Emission Displays --- p.13
Chapter 2.2.3 --- Parameters relevant to applications --- p.15
Chapter 2.3 --- The fabrication processes --- p.17
Chapter 2.3.1 --- The anisotropic wet etching method --- p.18
Chapter 2.3.2 --- The isotropic wet etching method --- p.19
Chapter 2.3.3 --- Field emission from coating materials --- p.20
Chapter 2.3.3.1 --- Coating enhancement --- p.20
Chapter 2.3.3.2 --- Diamond and diamond-like films --- p.21
Chapter 2.3.3.3 --- Metallic coatings --- p.22
Chapter 2.3.3.4 --- Porous silicon coatings --- p.22
Chapter 2.3.3.5 --- Silicon carbide coatings --- p.22
Chapter 2.3.4 --- Fabrication of field emitters with gate --- p.23
Chapter Chapter 3 --- Sample Preparation and Characterization Methods
Chapter 3.1 --- Sample preparation --- p.25
Chapter 3.2 --- The fabrication process
Chapter 3.2.1 --- Isotropic etching of silicon
Chapter 3.2.1.1 --- The anodization process --- p.25
Chapter 3.2.1.2 --- Porous silicon formation --- p.26
Chapter 3.2.2 --- Anistropic etching of silicon --- p.27
Chapter 3.2.3 --- The sputtering system --- p.28
Chapter 3.2.4 --- The MEVVA Ion Source Implanter --- p.30
Chapter 3.3 --- Characterization Methods
Chapter 3.3.1 --- Atomic Force Microscopy (AFM) --- p.32
Chapter 3.3.2 --- Scanning Electron Microscopy (SEM) --- p.34
Chapter 3.3.3 --- Field emission measurement
Chapter 3.3.3.1 --- Vacuum requirements --- p.35
Chapter 3.3.3.2 --- Testing system
Chapter 3.3.3.3 --- Fluctuation of field emission --- p.38
Chapter Chapter 4 --- Fabrication of Silicon Tips and their field emission charateristics
Chapter 4.1 --- The anodization etching process
Chapter 4.1.1 --- Introduction --- p.40
Chapter 4.1.2 --- Experimental details --- p.42
Chapter 4.1.3 --- Results and Discussions
Chapter 4.1.3.1 --- N type (100) sample --- p.45
Chapter 4.1.3.2 --- Ntype(lll) sample --- p.60
Chapter 4.1.3.3 --- Fluctuations of the emission current --- p.64
Chapter 4.1.3.4 --- The effect of Concentration of HF solution on First Step Anodization --- p.68
Chapter 4.1.3.5 --- The effect of the Concentration of HF solution on Second Step Anodization --- p.70
Chapter 4.1.3.6 --- Gated silicon field emitter --- p.70
Chapter 4.1.4 --- Conclusions --- p.73
Chapter 4.2 --- Anisotropic texturing process
Chapter 4.2.1 --- Introduction --- p.74
Chapter 4.2.2 --- Experimental details --- p.76
Chapter 4.2.3 --- Results and Discussions --- p.78
Chapter 4.2.4 --- Conclusion --- p.92
Chapter 4.3 --- Formation of Porous Silicon Layer on silicon
Chapter 4.3.1 --- Introduction --- p.93
Chapter 4.3.2 --- Experimental details --- p.94
Chapter 4.3.3 --- Results and Discussions --- p.95
Chapter 4.3.4 --- Conclusion --- p.100
Chapter 4.4 --- Chapter Summary --- p.101
Chapter Chapter 5 --- Improvement in the field emission characteristics of the silicon tips upon coating with low work function materials
Chapter 5.1 --- Amorphous carbon coating
Chapter 5.1.1 --- Introduction --- p.102
Chapter 5.1.2 --- Experimental details --- p.103
Chapter 5.1.3 --- Results and Discussions --- p.104
Chapter 5.1.4 --- Conclusion --- p.118
Chapter 5.2 --- Silicon carbide coated Silicon emitter by MEWA
Chapter 5.2.1 --- Introduction --- p.119
Chapter 5.2.2 --- Experimental details --- p.120
Chapter 5.2.3 --- Results and Discussions --- p.121
Chapter 5.2.4 --- Conclusion --- p.125
Chapter 5.3 --- Chapter Summary --- p.126
Chapter Chapter 6 --- Conclusions --- p.127
Reference --- p.134
List of publications --- p.140
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Hilbert, Shawn A. "Pulse propagation of sound, light, and electrons." 2009. http://proquest.umi.com/pqdweb?did=1694329141&sid=3&Fmt=2&clientId=14215&RQT=309&VName=PQD.
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Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009.Title from title screen (site viewed June 26, 2009). PDF text: xiii, 178 p. : ill. ; 10 Mb. UMI publication number: AAT 3350448 . Includes bibliographical references. Also available in microfilm and microfiche formats.
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"A study of field emission properties of ion beam synthesized and modified SiC layers on Si." 2002. http://library.cuhk.edu.hk/record=b5891293.
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Tsang Wei Mong.Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.
Includes bibliographical references (leaves 86-93).
Abstracts in English and Chinese.
Abstract --- p.i
Acknowledgement --- p.iv
Contents --- p.v
List of Figure Captions --- p.vi
List of Table Captions --- p.vii
Chapter Chapter 1 --- Introduction
Chapter 1.1 --- Introduction --- p.1
Chapter 1.2 --- Theory of Electron Field Emission --- p.1
Chapter 1.2.1 --- Fowler Nordheim Planar Field Emission Model for Metal --- p.2
Chapter 1.3 --- Goal of this Project --- p.9
Chapter Chapter 2 --- Sample Preparation and Characterization Methods
Chapter 2.1 --- Sample Preparation --- p.12
Chapter 2.1.1 --- MEVVA Implantation System --- p.13
Chapter 2.1.2 --- Implantation Conditions --- p.16
Chapter 2.1.3 --- Simulation by SRIM --- p.17
Chapter 2.2 --- Characterization Methods --- p.20
Chapter 2.2.1 --- AFM and CAFM --- p.20
Chapter 2.2.2 --- RBS --- p.22
Chapter 2.2.3 --- XPS --- p.24
Chapter 2.2.4 --- XRD --- p.27
Chapter 2.2.5 --- TEM --- p.28
Chapter 2.2.6 --- FE Measurement --- p.29
Chapter Chapter 3 --- FE Properties of IBS SiC layers
Chapter 3.1 --- Introduction --- p.31
Chapter 3.2 --- Field Enhancement Mechanisms for the IBS SiC Layers --- p.32
Chapter 3.3 --- Embedded Conducting Grains (ECG) Model of Local Field Enhancement --- p.45
Chapter 3.4 --- The Role of Conducting Grains in Field Enhancement --- p.48
Chapter Chapter 4 --- FE Properties of W modified IBS SiC layer
Chapter 4.1 --- Introduction --- p.58
Chapter 4.2 --- Experimental --- p.59
Chapter 4.3 --- Phase and Structural Evolution of W Modified IBS SiC Layers --- p.60
Chapter 4.3.1 --- XRD Results --- p.60
Chapter 4.3.2 --- XPS Results --- p.64
Chapter 4.3.3 --- TEM Results --- p.69
Chapter 4.3.4 --- AFM Results --- p.74
Chapter 4.4 --- Field Emission Properties --- p.76
Chapter Chapter 5 --- Conclusion --- p.84
Reference --- p.86
List of Publications --- p.94
Appendix --- p.96
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SHARMA, ANAND. "FIELD EMISSION OF ELECTRONS FROM HEMISPHERICAL CONDUCTING CARBON NANOTUBE TIP INCLUDING THE EFFECT OF IMAGE FORCE." Thesis, 2016. http://dspace.dtu.ac.in:8080/jspui/handle/repository/14632.
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ABSTRACT
The present work examines the field emission from Conducting Hemispherical Carbon Nanotune (CNT) tip including the Effect of Image Force. An expression for electrostatic potential for a Hemispherical CNT tip at a distance from the centre of CNT has been derived. Using the time-independent Schrodinger equation corresponding expressions for transmission coefficient and field emission current density have been derived for the Hemispherical Conducting Carbon Nanotubes. The numerical calculations of potential, transmission coefficient and the current density function have been calculated for a typical set of carbon nanotube parameters. From the expression of potential energy we found that the potential energy for the hemispherical CNT tip first increases and then decreases with the radial distance. The transmission coefficient increases with the normalized radial energy. And the current density function also increases with the normalized Fermi energy. An important outcome of the present work is that both transmission coefficient and field emission current density function decreases as the hemispherical CNT tip radius increases.
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Chen, Yi Wen Wang Ben. "Nanotube and nanofiber buckypaper cold cathode illumination experimental investigation /." 2006. http://etd.lib.fsu.edu/theses/available/etd-07102006-161808.
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Thesis (M.S.)--Florida State University, 2006.Advisor: Ben Wang, Florida State University, College of Engineering, Dept. of Industrial Engineering. Title and description from dissertation home page (viewed Sept. 22, 2006). Document formatted into pages; contains xii, 93 pages. Includes bibliographical references.
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Liao, Po-Hsinag, and 廖柏翔. "Development of Field Emission Electron Gun for Desktop Electron Microscope." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3d5ybg.
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碩士國立清華大學
工程與系統科學系
106
With the development of technology, electron microscope has become an important observational tool in different major such as physics, chemistry, biology, and materials engineering. The source of electron microscope, it usually divide into two types, thermionic type and field emission type. Field emission type electron source usually have smaller tip radius than thermal type, so it can produce smaller electron source. Then, electron beam pass by condenser lens, a small spot size source is formed. Therefore, the brightness of the electron gun is much brighter than thermal type source. In addition, field emission source spectral energy distribution is close to monochromatic, and has smaller energy spread. So field emission source has better coherence that lead it obtain higher resolution. Although field-emission type electron gun have above advantages, but it need to maintain in high vacuum condition. Because the tip of the field emission electron gun can easily react with impurities in the air, and lead the needle tip blunt. When the needle tip is blunt, it will cause the field emission gun poor efficiency. So the field emission type electron gun needs lots of high vacuum equipment to maintain it stay in high vacuum condition and high efficiency. The purpose of this research is using cheaper and more convenient ways to produce a field emission electron gun tip. And then set it up on our lab’s group made Desktop Electron Microscope to improve the resolution. In this paper, we successfully fabricated a field electron gun tip using electrolytic machining. The radius of curvature of the electron gun tip is about 100 nm or less, and its reproduction rate is also high. Finally, we also tried to deposit ZrO on the tip to make thermionic (Schottky) type field electron gun. After that, we also design some components installed on our Desktop Electron Microscope to finish field emission microscope.
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Liu, Cheng-Ting, and 劉正霆. "Synthesis of carbon nanocoils for electron field emission application." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/41837239808384967366.
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碩士大同大學
電機工程學系(所)
105
In this thesis we use the thermal chemical vapor deposition system to grow the carbon nanocoils and apply them to field emission devices. Firstly, we use the photolithograpic process to define the arrays of hole patterns. Secondly, we use the plasma etching system to remove the Mo layer and wet etching to remove the SiO2 layer and form the holes on Si substrate. Finally, we grow the carbon nanocoils outo the arrays of Mo/SiO2/Si substrate. We compare the field emission characteristics between the diode and triode structures. The results show that the gate of the triode structure is beneficial to pull the electrons. We also try to add phosphors on the anode to observe the lighting phenomenon. The results also show that the lighting phenomenon of the carbon nanocoils is superior to that of the carbon nanotubes in the triode structure.
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RACHANA. "FIELD EMISSION OF ELECTRONS BY TAKING INTO ACCOUNT THE DISTRIBUTION OF CHARGE ALONG THE LENGTH OF METALLIC CARBON NANOTUBES (CNTS)." Thesis, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/19026.
Full textAbstract:
An mathematical expression has been derived and analysed for total potential
energy V and field emission current density function ϕ of emitted electrons by
taking into account the distribution of charge along the length of the carbon
nanotubes (CNTs), matching to the representation for the tunnelling coefficient.
This tunnelling coefficient is obtained from solving of the time independent
Schrödinger’s wave equation. Mathematical calculations for the potential
energy V, tunnelling coefficient T and current density function ϕ have been
worked out for a distinctive set of the CNTs factors. It is concluded that the
potential energy in ergs declines with the radial distance r but increases with z coordinate along the length of the CNT. Moreover, the current density function
at the spherical CNT tip is substantially larger than along the length of
cylindrical metallic CNT. In addition, the field emission current density
function decreases with radius of CNTs in both the cases (i.e., cylindrical and
spherical tip). Some of our theoretical results are in agreement with the current
experimental observations.
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Liu, Feng Xiang, and 劉鳳翔. "Processes and Research of Carbon Nanotube Field Emission Electron Source." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/18022103617842045982.
Full textAbstract:
碩士中華大學
電機工程學系碩士班
90
In this thesis, we research field emission characteristic of Carbon Nanotubes, and fabricate the CNTs cathode. Carbon nanotubes (CNTs) cold cathodes were fabricated to replace the hot cathodes of cathode ray tubes (CRTs), because conventional hot cathode must be heated about 680℃. But now we don’t heat the cathode by using Carbon Nanotubes in this work. We just used a DC bias，then the emitter current was emitted to vacuum. It was compared Arc CNTs’ and CVD CNTs’ field emission characteristic, and used a printer to print the cathode once or twice. Then we use a tape to enhance field emission current. In this research, Arc CNTs’ field emission characteristic is better than CVD CNTs’, the result makes us to know that structure is very important. We also packaged the cathode to measured the I-V curve in a 17-inch CRT using the traditional method, and find a good result. Finally, we use nanosize Silver particle, because find a problem by SEM. And we believe the method can be better than previous method.
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Natarajan, Srividya. "A Study of Field Emission Based Microfabricated Devices." Diss., 2008. http://hdl.handle.net/10161/675.
Full textAbstract:
The primary goals of this study were to demonstrate and fully characterize a microscale ionization source (i.e. micro-ion source) and to determine the validity of impact ionization theory for microscale devices and pressures up to 100 mTorr. The field emission properties of carbon nanotubes (CNTs) along with Micro-Electro-Mechanical Systems (MEMS) design processes were used to achieve these goals. Microwave Plasma-enhanced CVD was used to grow vertically aligned Multi-Walled Carbon Nanotubes (MWNTs) on the microscale devices. A 4-dimensional parametric study focusing on CNT growth parameters confirmed that Fe catalyst thickness had a strong effect on MWNT diameter. The MWNT growth rate was seen to be a strong function of the methane-to-ammonia gas ratio during MWNT growth. A high methane-to-ammonia gas ratio was selected for MWNT growth on the MEMS devices in order to minimize growth time and ensure that the thermal budget of those devices was met.
A CNT-enabled microtriode device was fabricated and characterized. A new aspect of this device was the inclusion of a 10 micron-thick silicon dioxide electrical isolation layer. This thick oxide layer enabled anode current saturation and performance improvements such as an increase in dc amplification factor from 27 to 600. The same 3-panel device was also used as an ionization source. Ion currents were measured in the 3-panel micro-ion source for helium, argon, nitrogen and xenon in the 0.1 to 100 mTorr pressure range. A linear increase in ion current was observed for an increase in pressure. However, simulations indicated that the 3-panel design could be modified to improve performance as well as better understand device behavior. Thus, simulations and literature reports on electron impact ionization sources were used to design a new 4-panel micro-ion source. The 4-panel micro-ion source showed an approximate 10-fold performance improvement compared to the 3-panel ion source device. The improvement was attributed to the increased electron current and improved ion collection efficiency of the 4-panel device. Further, the same device was also operated in a 3-panel mode and showed superior performance compared to the original 3-panel device, mainly because of increased ion collection efficiency.
The effect of voltages applied to the different electrodes in the 4-panel micro-ion source on ion source performance was studied to better understand device behavior. The validity of the ion current equation (which was developed for macroscale ion sources operating at low pressures) in the 4-panel micro-ion source was studied. Experimental ion currents were measured for helium, argon and xenon in the 3 to 100 mTorr pressure range. For comparison, theoretical ion currents were calculated using the ion current equation for the 4-panel micro-ion source utilizing values calculated from SIMION simulations and measured electron currents. The measured ion current values in the 3 to 20 mTorr pressure range followed the calculated ion currents quite closely. A significant deviation was observed in the 20-100 mTorr pressure range. The experimental ion current values were used to develop a corrected empirical model for the 4-panel micro-ion source in this high pressure range (i.e., 3 to 100 mTorr). The role of secondary electrons and electron path lengths at higher pressures is discussed.
Dissertation
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Chen, Chia-Huan, and 陳嘉桓. "Analysis of Field Electron Emission Characteristics of Chemically Modified Carbon Nanotubes." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/06697097125512745040.
Full textAbstract:
碩士國立臺灣科技大學
光電工程研究所
97
Carbon nanotubes (CNTs) were synthesized on carbon cloth by thermal chemical vapor deposition (TCVD). To enhance the field emission current, catalyst metal at the tip of CNTs was removed by chemical modifications with nitric acid (HNO3). The field emission characteristics of CNTs with various HNO3 immersion time were investigated. As a result, when the HNO3 immersion time was 15 min, the threshold electric field (Eth) has the lowest value of 1.9 V/um. When the immersion time was extended, the Eth increased due to defects at the surface of CNTs. Although the Eth was decreased with the optimal condition of HNO3 treatment, the long-term stability of as treated CNTs was poor. To improve the stability, ZnO nanostructures were synthesized on the surface of the open-end CNTs. Consequently, the long-term stability of the CNTs was improved and an even lower Eth, i.e. 1.5 V/um, was obtained.