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No description available.

Vacuum field emission devices have become a promising candidate for emerging display technology due to their interesting properties compared to conventional thermionic emission devices that require high temperature and power to operate. Unlike thermionic emission, field emission devices can induce the electrons to emit at low temperature; sharp and thin emitters on the cathode are desired in order to increase the field emission. Many candidates from other research groups, such as Carbon Nanotubes (CNTs), SiC and ZnO, appear to have high field emission, but their complicated fabrication processes are the drawback. The silicon nanowhiskers produced by Geological & Nuclear Sciences (GNS) using Electron-Beam Rapid Thermal Annealing (EB-RTA) are an alternative material that is fast, inexpensive and uncomplicated to produce. They are based on the thermal desorption of silicon oxide, which forms silicon nanowhiskers on the silicon wafer in a short duration. Field emission diode structures on Silicon on Insulator (SOI) wafers were fabricated in order to investigate the field emission due to these GNS silicon nanowhiskers. An uncomplicated fabrication process using photolithography and etching process was developed. Electron beam lithography (EBL) was also used to create the different feature sizes directly onto the SOI wafer. The silicon nanowhiskers grown on these structures are as high as 35 nm with density distribution up to 30 µm⁻¹. The electrical characteristics of these devices are diode-like when the voltage range from -40 V to 40 V is applied. The best samples produced an emitted current as high as 2 mA, which is suitable for many applications, such as flat panel displays, x-ray sources and high frequency devices. However, in some cases, the diode structures failed to show the diode-like characteristics, perhaps as a result of bad contact connections or the emitters have been worn out after applying high voltage for some time. Device life time and stability were also considered and investigated via a number of electrical measurements for a period of time as long as one hour in this study. Even though these nanowhiskers have shown promising results, there are still many aspects to be considered to improve the experiments, such as the vacuum system and better contacts.

Thesis (M.E.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (p. 87-96). Also available via the World Wide Web.

<p>Carbon nanotubes (CNTs) have recently emerged as promising candidates for electron field emission (FE) cathodes in integrated FE devices. These nanostructured carbon materials possess exceptional properties and their synthesis can be thoroughly controlled. Their integration into advanced electronic devices, including not only FE cathodes, but sensors, energy storage devices, and circuit components, has seen rapid growth in recent years. The results of the studies presented here demonstrate that the CNT field emitter is an excellent candidate for next generation vacuum microelectronics and related electron emission devices in several advanced applications.</p><p> The work presented in this study addresses determining factors that currently confine the performance and application of CNT-FE devices. Characterization studies and improvements to the FE properties of CNTs, along with Micro-Electro-Mechanical Systems (MEMS) design and fabrication, were utilized in achieving these goals. Important performance limiting parameters, including emitter lifetime and failure from poor substrate adhesion, are examined. The compatibility and integration of CNT emitters with the governing MEMS substrate (i.e., polycrystalline silicon), and its impact on these performance limiting parameters, are reported. CNT growth mechanisms and kinetics were investigated and compared to silicon (100) to improve the design of CNT emitter integrated MEMS based electronic devices, specifically in vacuum microelectronic device (VMD) applications.</p><p> Improved growth allowed for design and development of novel cold-cathode FE devices utilizing CNT field emitters. A chemical ionization (CI) source based on a CNT-FE electron source was developed and evaluated in a commercial desktop mass spectrometer for explosives trace detection. This work demonstrated the first reported use of a CNT-based ion source capable of collecting CI mass spectra. The CNT-FE source demonstrated low power requirements, pulsing capabilities, and average lifetimes of over 320 hours when operated in constant emission mode under elevated pressures, without sacrificing performance. Additionally, a novel packaged ion source for miniature mass spectrometer applications using CNT emitters, a MEMS based Nier-type geometry, and a Low Temperature Cofired Ceramic (LTCC) 3D scaffold with integrated ion optics were developed and characterized. While previous research has shown other devices capable of collecting ion currents on chip, this LTCC packaged MEMS micro-ion source demonstrated improvements in energy and angular dispersion as well as the ability to direct the ions out of the packaged source and towards a mass analyzer. Simulations and experimental design, fabrication, and characterization were used to make these improvements.</p><p> Finally, novel CNT-FE devices were developed to investigate their potential to perform as active circuit elements in VMD circuits. Difficulty integrating devices at micron-scales has hindered the use of vacuum electronic devices in integrated circuits, despite the unique advantages they offer in select applications. Using a combination of particle trajectory simulation and experimental characterization, device performance in an integrated platform was investigated. Solutions to the difficulties in operating multiple devices in close proximity and enhancing electron transmission (i.e., reducing grid loss) are explored in detail. A systematic and iterative process was used to develop isolation structures that reduced crosstalk between neighboring devices from 15% on average, to nearly zero. Innovative geometries and a new operational mode reduced grid loss by nearly threefold, thereby improving transmission of the emitted cathode current to the anode from 25% in initial designs to 70% on average. These performance enhancements are important enablers for larger scale integration and for the realization of complex vacuum microelectronic circuits.</p> / Dissertation

Este trabalho apresenta um método de fabricação de micropontas de silício que já contém os contatos elétricos integrados à sua estrutura. O processo de fabricação das microestruturas é o foco desta pesquisa e nossa motivação futura é desenvolver dispositivos para emissão eletrônica por efeito de campo (Field Emission Devices - FED. O método em questão baseia-se: (i) no underetch anisotrópico, que ocorre em substratos de silício (100) quando orientados de maneira conveniente, em solução de KOH; (ii) na utilização de filme de oxinitreto de silício (SiOxNy), que visa o mascaramento no processo de corrosão durante a formação das micropontas e também, o suporte mecânico para as trilhas metálicas que formam o eletrodo de polarização. Tal material, obtido por Deposição Química a Vapor assistida por Plasma (Plasma Enhanced Chemical Vapour Deposition - PECVD), apresenta baixo stress interno e tem a função de isolar eletricamente os eletrodos do substrato de Si. Esse filme de SiOxNy viabilizou a obtenção de trilhas autosustentadas, planas e lisas, com dimensões de até 6 milímetros. Através de técnicas convencionais de fotolitografia construímos contatos elétricos de cromo auto-alinhados sobre as micropontas. Metodologicamente definimos e caracterizamos, por meio de microscopia óptica, diferentes etapas da formação das micropontas, determinamos suas respectivas taxas de corrosão e consequentemente o tempo total de sua formação, em função das dimensões iniciais da máscara. As estruturas foram fabricadas na forma de matrizes com 50, 98, 112 e 113 micropontas. O espaçamento entre elas varia de 130 a 450 ?m. O diâmetro do ápice e a altura são de aproximadamente 1 e 54 ?m respectivamente. A principal vantagem deste método de fabricação é a eliminação da necessidade de utilização de microposicionadores externos e de acionamento manual, para a integração de contatos elétricos à estrutura. Finalmente, o êxito deste método deveu-se essencialmente às propriedades exclusivas do filme de SiOxNy. / This work presents a fabrication method of silicon microtips with integrated electrical contacts into the structure. Our motivation is the future development of field emission devices - FED, however our focus in this research is the microstructure fabrication process. This method is based on: (i) anisotropic under-etch method that occurs in the silicon substrate (100), when it is oriented in convenient crystallographic direction, using KOH solution; (ii) the employment of silicon oxinitride films (SiOxNy) which aims to mask the corrosion process during the formation of the microtips, and also to give mechanically support for the metallic tracks of their electrodes. Such material, which is obtained by Plasma Enhanced Chemical Vapour Deposition - PECVD, exhibits internal low stress and was used to obtain electric insulation between the electrodes and the Si substrate. These SiOxNy films made possible the achievement of flat and smooth selfsustained tracks, whose dimensions can reach 6 millimeters. Through conventional photolitographic techniques, we built chromium self-aligned electrical contacts on those microtips. Methodologically, we define and characterize different stages of microtips formation, by means of optical microscopy, and we determine their respective etch rates. And consequently the entire formation time in function of the initial mask dimensions. Those structures had been manufactured in the shape of matrices with 50, 98, 112 and 113 microtips which distance between each other can vary from 130 to 450 ?m. Its diameter in the microtip apex and its height are about 1 and 54 ?m respectively. The main advantage of this fabrication method is the lack of the requirement of manual external micropositioners for the integration of electrical contacts to structure itself. Finally, this method succeeds due essentially to the SiOxNy exclusive film properties.

Este trabalho apresenta um método de fabricação de micropontas de silício que já contém os contatos elétricos integrados à sua estrutura. O processo de fabricação das microestruturas é o foco desta pesquisa e nossa motivação futura é desenvolver dispositivos para emissão eletrônica por efeito de campo (Field Emission Devices - FED. O método em questão baseia-se: (i) no underetch anisotrópico, que ocorre em substratos de silício (100) quando orientados de maneira conveniente, em solução de KOH; (ii) na utilização de filme de oxinitreto de silício (SiOxNy), que visa o mascaramento no processo de corrosão durante a formação das micropontas e também, o suporte mecânico para as trilhas metálicas que formam o eletrodo de polarização. Tal material, obtido por Deposição Química a Vapor assistida por Plasma (Plasma Enhanced Chemical Vapour Deposition - PECVD), apresenta baixo stress interno e tem a função de isolar eletricamente os eletrodos do substrato de Si. Esse filme de SiOxNy viabilizou a obtenção de trilhas autosustentadas, planas e lisas, com dimensões de até 6 milímetros. Através de técnicas convencionais de fotolitografia construímos contatos elétricos de cromo auto-alinhados sobre as micropontas. Metodologicamente definimos e caracterizamos, por meio de microscopia óptica, diferentes etapas da formação das micropontas, determinamos suas respectivas taxas de corrosão e consequentemente o tempo total de sua formação, em função das dimensões iniciais da máscara. As estruturas foram fabricadas na forma de matrizes com 50, 98, 112 e 113 micropontas. O espaçamento entre elas varia de 130 a 450 ?m. O diâmetro do ápice e a altura são de aproximadamente 1 e 54 ?m respectivamente. A principal vantagem deste método de fabricação é a eliminação da necessidade de utilização de microposicionadores externos e de acionamento manual, para a integração de contatos elétricos à estrutura. Finalmente, o êxito deste método deveu-se essencialmente às propriedades exclusivas do filme de SiOxNy. / This work presents a fabrication method of silicon microtips with integrated electrical contacts into the structure. Our motivation is the future development of field emission devices - FED, however our focus in this research is the microstructure fabrication process. This method is based on: (i) anisotropic under-etch method that occurs in the silicon substrate (100), when it is oriented in convenient crystallographic direction, using KOH solution; (ii) the employment of silicon oxinitride films (SiOxNy) which aims to mask the corrosion process during the formation of the microtips, and also to give mechanically support for the metallic tracks of their electrodes. Such material, which is obtained by Plasma Enhanced Chemical Vapour Deposition - PECVD, exhibits internal low stress and was used to obtain electric insulation between the electrodes and the Si substrate. These SiOxNy films made possible the achievement of flat and smooth selfsustained tracks, whose dimensions can reach 6 millimeters. Through conventional photolitographic techniques, we built chromium self-aligned electrical contacts on those microtips. Methodologically, we define and characterize different stages of microtips formation, by means of optical microscopy, and we determine their respective etch rates. And consequently the entire formation time in function of the initial mask dimensions. Those structures had been manufactured in the shape of matrices with 50, 98, 112 and 113 microtips which distance between each other can vary from 130 to 450 ?m. Its diameter in the microtip apex and its height are about 1 and 54 ?m respectively. The main advantage of this fabrication method is the lack of the requirement of manual external micropositioners for the integration of electrical contacts to structure itself. Finally, this method succeeds due essentially to the SiOxNy exclusive film properties.

Orientador: Marco Antonio Robert Alves / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e Computação / Made available in DSpace on 2018-08-05T19:44:58Z (GMT). No. of bitstreams: 1 Porto_LesnirFerreira_M.pdf: 4190794 bytes, checksum: 1dec9fdc0b3dd1bffb34d78bccf2648b (MD5) Previous issue date: 2005 / Resumo: Este trabalho de mestrado teve como objetivos a fabricação e o estudo do comportamento elétrico das ponteiras de silício de emissão de campo a vácuo (PECV) recobertas com filme fino de carbono tipo diamante (DLC). Apresentamos o processo de fabricação das ponteiras de silício que é realizado através das etapas de fotolitografia, corrosão por íon reativo no plasma de SF6 (hexafluoreto de enxofre), oxidação térmica seca para afinamento, e deposição do filme DLC por PECVD (Plasma Enhanced Chemical Vapor Deposition). Mostramos os resultados obtidos da caracterização elétrica das ponteiras sem o filme e com o filme DLC, através do levantamento das curvas características I x V (corrente x tensão) e I x t (corrente x tempo). Verificamos que as curvas I x V obedeceram ao modelo de emissão de elétrons de Fowler-Nordheim. Comparamos estes resultados a fim de avaliarmos as mudanças na tensão de limiar, corrente emitida, e estabilidade de emissão. Neste estudo fabricamos PECV recobertas por filme DLC com espessura de aproximadamente 170 Å / Abstract: The objectives of this dissertation were the fabrication of silicon field emitter tips coated with diamond like carbon (DLC) thin films, and the study of its electrical behavior. We present the fabrication process of silicon tips that consists on four stages: photolithography, reactive ion etching SF6 plasma, thermal oxidation for sharpening, and the DLC deposition by PECVD (Plasma Enhanced Chemical Vapor Deposition). We show results obtained from the electrical characterization of tips without film and tips with DLC, by the characteristics curves I x V (current x voltage) and I x t (current x time). Current-voltage measurements followed a Fowler-Nordheim electron emission behavior. We compare these results to evaluate the change of the threshold voltage, emitted current, and emission stability, as a function of the coating with the film. In this study we fabricated silicon tips coated with DLC film with thickness of approximately 170 Å / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Orientador: Marco Antonio Robert Alves / Dissertação (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