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Author : Benjamin L. Crossley
Publisher :
ISBN 13 :
Total Pages : 286 pages
Book Rating : 4.:/5 (777 download)
Download or read book Carbon Nanotube Field Emission Arrays written by Benjamin L. Crossley and published by . This book was released on 2011 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Yahachi Saito
Publisher : John Wiley & Sons
ISBN 13 : 3527632107
Total Pages : 551 pages
Book Rating : 4.5/5 (276 download)
Download or read book Carbon Nanotube and Related Field Emitters written by Yahachi Saito and published by John Wiley & Sons. This book was released on 2010-10-01 with total page 551 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes (CNTs) have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science. These characteristics include extraordinary strength, unique electrical properties, and the fact that they are efficient heat conductors. Field emission is the emission of electrons from the surface of a condensed phase into another phase due to the presence of high electric fields. CNT field emitters are expected to make a breakthrough in the development of field emission display technology and enable miniature X-ray sources that will find a wide variety of applications in electronic devices, industry, and medical and security examinations. This first monograph on the topic covers all aspects in a concise yet comprehensive manner - from the fundamentals to applications. Divided into four sections, the first part discusses the preparation and characterization of carbon nanotubes, while part two is devoted to the field emission properties of carbon nanotubes, including the electron emission mechanism, characteristics of CNT electron sources, and dynamic behavior of CNTs during operation. Part three highlights field emission from other nanomaterials, such as carbon nanowalls, diamond, and silicon and zinc oxide nanowires, before concluding with frontier R&D applications of CNT emitters, from vacuum electronic devices such as field emission displays, to electron sources in electron microscopes, X-ray sources, and microwave amplifiers. Edited by a pioneer in the field, each chapter is written by recognized experts in the respective fields.
Author :
Publisher :
ISBN 13 :
Total Pages : 4 pages
Book Rating : 4.:/5 (227 download)
Download or read book Integrally Gated Carbon Nanotube-on-Post Field Emitter Arrays written by and published by . This book was released on 2001 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes (cNT) are excellent field emitters on account of their chemical, structural, and electronic properties, which afford important aspects of robustness that have been lacking in the conventional metal and silicon field emitter arrays (FEA). They possess high current-carrying capacity and mechanical strength. Their small diameters (2-50 nm) and high aspect ratios produce high geometric field enhancement, which remains nearly constant even when material is removed from the end of the tubes such as by back ion bombardment. A key contributing factor to their stability as field emitters is the lack of surface oxide formation. Surface oxide formation on metal or silicon emitters impedes electron transport to the surface and causes changes in the emission characteristics during operation. Furthermore, the oxides could be the main cause for FEA catastrophic destruction by trapping charge which could lead to arcing. 1 It has also been suggested that carbon nanotubes do not form nanoprotrusions as metal and silicon cathodes do, thus making current runaway and arcing less likely to occur. 2.
Author : Niraj Narasinha Kulkarni
Publisher :
ISBN 13 :
Total Pages : 62 pages
Book Rating : 4.:/5 (59 download)
Download or read book Field emission from vertically aligned carbon nanotube arrays written by Niraj Narasinha Kulkarni and published by . This book was released on 2002 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jianfeng Wu
Publisher :
ISBN 13 :
Total Pages : 143 pages
Book Rating : 4.:/5 (668 download)
Download or read book Fabrication, Field Emission Properties and Theoretical Simulation of Triode-type Carbon Nanotube Emitter Arrays written by Jianfeng Wu and published by . This book was released on 2010 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes exhibit excellent field emission properties and will likely be prime candidates as electron sources in future vacuum electronic applications. Recent research has focused on enhancing field emission from traditional diode-type emitters by adding a gate electrode between the anode and the cathode. Since the gate to cathode (emitter) distance in this triode-type structure is small relative to the anode to cathode distance, this structure allows relatively small gate voltages to significantly enhance or dampen field emission. The key challenge for this research is: synthesizing vertically aligned carbon nanotube field emitters inside arrays of triode-type devices. The most common "top-down", etch-deposit-synthesis method of synthesizing carbon nanotubes inside gated cavities is discussed here, and a novel "bottom-up" method is presented. This new approach bypasses the lithography and wet chemistry essential to the etch-deposit-synthesis method, instead using a dual-beam focused ion beam (FIB) system to mill cavities into a multi-layered substrate. Here the substrate is designed such that the act of milling a hole simultaneously creates the gate structure and exposes the catalyst from which carbon nanotubes can then be grown. Carbon nanotubes are synthesized using plasma enhanced chemical vapor deposition (PECVD) rather than thermal chemical vapor deposition, due to the superior alignment of the PECVD growth. As dual-beam FIB and PECVD can both be largely computerized, this synthesis method is highly reproducible. The dual-beam FIB also permits a high degree of controllability in gate radius, cavity depth and emitter spacing. The effects of a host of PECVD growth parameters (initial catalyst thickness, gas concentration, growth temperature, temperature ramping rate, chamber pressure, and plasma voltage) were characterized so that the morphology of the carbon nanotube emitters could be controlled as well. This "bottom-up" method is employed to construct functional, large area carbon nanotube field emitter arrays (CNT FEAs). The role of the gate layer in field emission is examined experimentally as well as through theoretical models. Field emission testing revealed that increasing gate voltage by as little as 0.3 V had significant impact on the local electric fields, lowering the turn-on and threshold fields by 3.6 and 3.0 V/um, respectively, and increasing the field enhancement factor from 149 to 222. A quantum mechanical model of such triode-type field emission indicates that the local electric field generated by a negatively or positively biased gate directly impacts the tunneling barrier thickness and thus the achievable emission current. However, the geometry of triode-type devices (gate height, gate radius, emitter density) can influence the degree to which the gate voltage influences field emission. I demonstrate here an effective method of analytically calculating the effect of various such geometric parameters on the field emission. Results show that gate type (the height of the gate relative the emitter tip) can significantly impact the local electric field and hence the type of applications a device is suitable for. Side gates (gate height emitter height) induced the highest local electric field, while top gates (gate height emitter height) provided the greatest controllability. For all gate types, increasing the size of the gate opening increased the local electric field by diminishing the gate-emitter screening effect. However, gate voltages were able to enhance or inhibit the local electric field much more readily with smaller gate radii. Due to the strength of gate-emitter field screening in the triode-type structure, the spacing between emitters had virtually no impact on the local electric field, allowing relatively high emitter densities. These theoretical results, combined with a highly controllable synthesis method, provide valuable information and methodology for those designing and optimizing triode-type devices targeted at specific applications.
Author : Yunhan Li
Publisher :
ISBN 13 :
Total Pages : 151 pages
Book Rating : 4.:/5 (112 download)
Download or read book Carbon Nanotube Field Emitter Array and Its Application to Novel X-ray Systems written by Yunhan Li and published by . This book was released on 2018 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the emergence of ever more demanding X-ray imaging applications, including radiotherapy, radiography, computed tomography and tomosynthesis, there is a tendency to use field emission (FE) to take the place of thermionic emission in X-ray generation. Carbon nanotube (CNT) field emitter array (FEA) is able to provide enhanced current and low energy dispersion for X-ray generation. The low operating temperature, instantaneous response, and small size of CNT FEA enable efficient and controllable FE performance for high spatial and temporal resolution X-ray imaging and instantaneous switching among multiple X-ray sources. Challenges are still remaining for CNT FEA study and development. The first is the insufficient understanding of FE uniformity of CNT FEA and CNT emitter failure mechanism, which limits the development of stable and reliable CNT FEA. The second is the lack of applications of CNT FEA for the emergence of novel X-ray imaging applications that require dose adjustments, fluence field modulation, and shape variation. In this thesis, recent advances in CNT FE and field emitters are comprehensively reviewed. Issues related to the principles, characteristics, and applications of CNT based FE are discussed. The research starts with a fundamental study of understanding the FE uniformity and emitter failure mechanism of CNT FEA by designing and demonstrating a simple and reliable field emission microscopy method using PMMA (Poly (methyl methacrylate)) thin film with microscopic camera. This novel approach is able to resolve the challenges of observing FE uniformity of CNT FEA and CNT field emitter failure behaviour. The unique phenomenon of light emission and Coulomb explosion of CNT field emitter failure induced by FE is represented and systematically characterized, which is a combined effect of Joule heating and excessive charging. Then, individual ballast of vertically aligned CNT FEA using silicon current limiters is designed and fabricated, which exhibits improved reliability and stability. The CNT FEA is applied to a low-cost self-contained and self-focusing compact X-ray source integrated with resonant transformer. The X-ray source can be powered by low voltage to generate pulsed X-ray and achieve sub-millimetre resolution. Using finite element analysis and Monte Carlo simulation, CNT FEA based two dimensional multi-pixel X-ray source is designed and experimentally verified, which is feasible for X-ray fluence field modulation in next generation X-ray imaging systems.
Author : Zhifeng Ren
Publisher : Springer Science & Business Media
ISBN 13 : 3642304907
Total Pages : 310 pages
Book Rating : 4.6/5 (423 download)
Download or read book Aligned Carbon Nanotubes written by Zhifeng Ren and published by Springer Science & Business Media. This book was released on 2012-09-05 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gives a survey of the physics and fabrication of carbon nanotubes and their applications in optics, electronics, chemistry and biotechnology. It focuses on the structural characterization of various carbon nanotubes, fabrication of vertically or parallel aligned carbon nanotubes on substrates or in composites, physical properties for their alignment, and applications of aligned carbon nanotubes in field emission, optical antennas, light transmission, solar cells, chemical devices, bio-devices, and many others. Major fabrication methods are illustrated in detail, particularly the most widely used PECVD growth technique on which various device integration schemes are based, followed by applications such as electrical interconnects, nanodiodes, optical antennas, and nanocoax solar cells, whereas current limitations and challenges are also be discussed to lay the foundation for future developments.
Author : Yahachi Saito
Publisher : CRC Press
ISBN 13 : 1000333795
Total Pages : 374 pages
Book Rating : 4.0/5 (3 download)
Download or read book Nanostructured Carbon Electron Emitters and Their Applications written by Yahachi Saito and published by CRC Press. This book was released on 2022-01-27 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon forms a variety of allotropes due to the diverse hybridization of s- and p-electron orbitals, including the time-honored graphite and diamond as well as new forms such as C60 fullerene, nanotubes, graphene, and carbyne. The new family of carbon isotopes—fullerene, nanotubes, graphene, and carbyne—is called “nanostructured carbon” or “nanocarbon.” These isotopes exhibit extreme properties such as ultrahigh mechanical strength, ultrahigh charge–carrier mobility, and high thermal conductivity, attracting considerable attention for their electronic and mechanical applications as well as for exploring new physics and chemistry in the field of basic materials science. Electron sources are important in a wide range of areas, from basic physics and scientific instruments to medical and industrial applications. Carbon nanotubes (CNTs) and graphene behave as excellent electron-field emitters owing to their exceptional properties and offer several benefits compared to traditional cathodes. Field emission (FE) produces very intense electron currents from a small surface area with a narrow energy spread, providing a highly coherent electron beam—a combination that not only provides us with the brightest electron sources but also explores a new field of electron beam–related research. This book presents the enthusiastic research and development of CNT-based FE devices and focuses on the fundamental aspects of FE from nanocarbon materials, including CNTs and graphene, and the latest research findings related to it. It discusses applications of FE to X-ray and UV generation and reviews electron sources in vacuum electronic devices and space thrusters. Finally, it reports on the new forms of carbon produced via FE from CNT.
Author : Mark Schulz
Publisher : William Andrew
ISBN 13 : 1455778648
Total Pages : 861 pages
Book Rating : 4.4/5 (557 download)
Download or read book Nanotube Superfiber Materials written by Mark Schulz and published by William Andrew. This book was released on 2013-09-16 with total page 861 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotube Superfiber Materials refers to different forms of macroscale materials with unique properties constructed from carbon nanotubes. These materials include nanotube arrays, ribbons, scrolls, yarn, braid, and sheets. Nanotube materials are in the early stage of development and this is the first dedicated book on the subject. Transitioning from molecules to materials is a breakthrough that will positively impact almost all industries and areas of society. Key properties of superfiber materials are high flexibility and fatigue resistance, high energy absorption, high strength, good electrical conductivity, high maximum current density, reduced skin and proximity effects, high thermal conductivity, lightweight, good field emission, piezoresistive, magnetoresistive, thermoelectric, and other properties. These properties will open up the door to dozens of applications including replacing copper wire for power conduction, EMI shielding, coax cable, carbon biofiber, bullet-proof vests, impact resistant glass, wearable antennas, biomedical microdevices, biosensors, self-sensing composites, supercapacitors, superinductors, hybrid superconductor, reinforced elastomers, nerve scaffolding, energy storage, and many others. The scope of the book covers three main areas: Part I: Processing; Part II: Properties; and Part III: Applications. Processing involves nanotube synthesis and macro scale material formation methods. Properties covers the mechanical, electrical, chemical and other properties of nanotubes and macroscale materials. Different approaches to growing high quality long nanotubes and spinning the nanotubes into yarn are explained in detail. The best ideas are collected from all around the world including commercial approaches. Applications of nanotube superfiber cover a huge field and provides a broad survey of uses. The book gives a broad overview starting from bioelectronics to carbon industrial machines. First book to explore the production and applications of macro-scale materials made from nano-scale particles Sets out the processes for producing macro-scale materials from carbon nanotubes, and describes the unique properties of these materials Potential applications for CNT fiber/yarn include replacing copper wire for power conduction, EMI shielding, coax cable, carbon biofiber, bullet-proof vests, impact resistant glass, wearable antennas, biomedical microdevices, biosensors, self-sensing composites, supercapacitors, superinductors, hybrid superconductor, reinforced elastomers, nerve scaffolding, energy storage, and many others
Author : Janglin Chen
Publisher : Springer
ISBN 13 : 9783540795681
Total Pages : 2700 pages
Book Rating : 4.7/5 (956 download)
Download or read book Handbook of Visual Display Technology written by Janglin Chen and published by Springer. This book was released on 2012-01-23 with total page 2700 pages. Available in PDF, EPUB and Kindle. Book excerpt: This handbook offers a comprehensive description of the science, technology, economic and human interface factors associated with the displays industry. With expert contributions from over 150 international display professionals and academic researchers, it covers all classes of display device and discusses established principles, emergent technologies, and particular areas of application.
Author : O. Groning
Publisher :
ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.:/5 (228 download)
Download or read book From Diamond to Carbon Nanotube Field Emitter written by O. Groning and published by . This book was released on 2001 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper we review the physics and the expectations that were put into the negative electron affinity (NEA) mediated field emission of chemical vapor deposition CVD diamond films and how the emitter technology made possible by this mechanism could have challenged the classical metal micro-tip field emitter arrays. We discuss the dependency between emitter performance of micro-tip emitter arrays and feature size (size of the field enhancing tip) and due to this to the connection between emitter performance and fabrication costs. We introduce the concept of the field enhancement distribution function f(beta) for a useful characterization of the field emission properties of thin film emitter and show how this distribution function can be measured by scanning anode field emission microscopy. Using 1(beta) measured on a thin film of randomly oriented multiwalled carbon nanotubes we show that even these kinds of low cost emitters can show a field emission performance comparable to micro-tip arrays, yet that the large spread in field enhancement values between the individual emitter prevent this performance to be fully exploited. This because the field range in which such thin film emitters can be operated is limited due to emitter disruption and triggering of vacuum arcs. Simulations show how resistor-limited emission can solve these limitations.
Author : Martin Dionne
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (713 download)
Download or read book Optimized Carbon Nanotube Array Cathodes for Thermo-field Emission in Plasmas written by Martin Dionne and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Alexander Kuznetsov
Publisher :
ISBN 13 :
Total Pages : 190 pages
Book Rating : 4.:/5 (298 download)
Download or read book Physics of Electron Field Emission by Self-assembled Carbon Nanotube Arrays written by Alexander Kuznetsov and published by . This book was released on 2008 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Extensive study of electrochemical charge injection of CNTs and its applications in electron field emission was performed. It was shown that work function of carbon nanotubes can be tuned in a wide range by means of electrochemical charging. The problem of charge dissipation in air is especially important for negative charging. It was found that larger size and higher valence of injected ions can significantly increase the stability of charging.
Author :
Publisher :
ISBN 13 :
Total Pages : 3 pages
Book Rating : 4.:/5 (15 download)
Download or read book Field Emission Properties of Carbon Nanotube Pillar Arrays Patterned Directly on Metal Alloy Surfaces written by and published by . This book was released on 2008 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotube pillar arrays (CPAs) for cold field emission were fabricated using a conventional photolithography process, and the geometry of these arrays was studied and the effect of pillar height on field emission was quantified. Our CPA samples achieved turn-on fields as low as 0.9 V/micrometer and stable current densities of 10 mA/cm(2) at applied field lower than 6V/micrometer.
Author : Hosam El-Din Saleh
Publisher : BoD – Books on Demand
ISBN 13 : 1789844010
Total Pages : 250 pages
Book Rating : 4.7/5 (898 download)
Download or read book Perspective of Carbon Nanotubes written by Hosam El-Din Saleh and published by BoD – Books on Demand. This book was released on 2019-12-11 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes belong to new nanomaterials and have been known for almost 20 years, but their history is somewhat lengthier. They have been identified as promising candidates for various applications.High-temperature preparation techniques are conventional techniques for the synthesis of carbon nanotubes using arc discharge or laser ablation, but today these methods are being replaced by low-temperature vapor deposition techniques, since orientation, alignment, nanotube length, diameter, purity, and density of carbon nanotubes can be precisely controlled. The synthesis of carbon nanotubes by chemical vapor deposition on catalyst arrays leads to nanotube models grown from specific sites on surfaces. The controlled synthesis of nanotubes opens up interesting possibilities in nanoscience and nanotechnologies, including electrical, mechanical and electromechanical properties and devices, chemical functionalization, surface chemistry and photochemistry, molecular sensors, and interfacing with moderate biological systems.Carbon nanotubes are used in many applications due to their unique electrical, mechanical, optical, thermal, and other properties. Conductive and high-strength composite materials, energy saving and energy conversion devices, sensors, visualization of field emissions and sources of radiation, means for storing hydrogen, and nanoscale semiconductor devices, probes, and interconnections are some of the many applications of carbon nanotubes.
Author : Yonghai Sun
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (126 download)
Download or read book Design and Fabrication of Carbon Nanotube Array Based Field Emission Cathode for X-ray Tube written by Yonghai Sun and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Field emission cathodes have proven themselves to be excellent candidates for some special medical X-ray applications. Spindt cathode and CNT (carbon nanotube) based field emission cathode have been widely studied for many years. Spindt cathode has the near perfect structure, but the material property limits its applications. On the other hand, low density vertically aligned CNT array has been proved the best candidate of field emission material. Several attempts have been made to combine the advantages of the Spindt cathode and CNT array, but some most important advantages of Spindt cathode have not been successfully utilized in CNT emitter design, for example: ballast resistor, self-aligned fabrication process, sub-micron scale gate electrode, and low control voltage. In this thesis, the design, fabrication and test of CNT based field emission cathode with a novel ballast resistor and coaxial cylinder shape gate electrode is reported. A connection pad has been reported for the first time. This structure makes the ballast resistor can be utilized in a CNT field emitter array. Therefore, the uniformity and stability of field emission current is improved significantly. In addition, the stabilized emission current heated up the sample to a high temperature and changes the emission from field emission to Schottky emission regime. This is the first report of the self-heating Schottky emission from a CNT emitter array. Coaxial cylinder shape gate electrode is another important improvement in the CNT emitter design. The gate electrode adopts the self-alignment property of the Spindt cathode, and adjusted to fit the structure and synthesis process of CNT array. This new design and fabrication process has all the advantages of both the Spindt cathode and CNT emitter. In addition to the field emission cathode design, a novel PMMA (poly methyl methacrylate) based FEM (field emission microscope) is designed to evaluate the emission uniformity and capture high resolution images of the distribution of field emitted electrons. Compare to the conventional phosphor screen based FEM, the PMMA based FEM has a much higher resolution and sensitivity. Images of this new FEM have a resolution of as high as 0.34 nm and clearly show the boundary of crystal facets.
Author : Graham Patrick Sanborn
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (88 download)
Download or read book A Thin Film Triode Type Carbon Nanotube Field Electron Emission Cathode written by Graham Patrick Sanborn and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 Î1/4A/cmÂ2 at the anode and 1.68 mA/cmÂ2 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.
