Download or read book Microscopic Characterization of Electron Field Emission from Carbon Nanotubes and Carbon Thin film Electron Emitters written by Lars-Ola Nilsson and published by . This book was released on 2001 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microscopic Characterization of Electron Field Emission from Carbon Nanotubes and Carbon Thin film Electron Emitters written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electron Microscopy of Nanotubes written by and published by 清华大学出版社有限公司. This book was released on 2004 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: 本书用英文的形式分析了纳米管电子显微。

Download or read book Characterization of Carbon Nanotube Based Thin Film Field Emitter written by Niraj Sinha and published by . This book was released on 2008 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, carbon nanotubes (CNTs) have emerged as one of the best field emitters for a variety of technological applications. The field emitting cathodes have several advantages over the conventional thermionic cathodes: (i) current density from field emission would be orders of magnitude greater than in the thermionic case, (ii) a cold cathode would minimize the need for cooling, and (iii) a field emitting cathode can be miniaturized. In spite of good performance of such cathodes, the procedure to estimate the device current is not straight forward and the required insight towards design optimization is not well understood. In addition, the current in CNT-based thin film devices shows fluctuation. Such fluctuation in field emission current is not desirable for many biomedical applications such as x-ray devices. The CNTs in a thin film undergo complex dynamics during field emission, which includes processes such as (i) evolution, (ii) electromechanical interaction, (iii) thermoelectric heating, (iv) ballistic transport, and (v) electron gas flow. These processes are coupled and nonlinear. Therefore, they must be analyzed accurately from the stability and long-term performance point of view. In this research, we develop detailed physics-based models of CNTs considering the aspects mentioned above.

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.

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.

Download or read book Modern Developments in Vacuum Electron Sources written by Georg Gaertner and published by Springer Nature. This book was released on 2020-10-09 with total page 609 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gives an overview of modern cathodes and electron emitters for vacuum tubes and vacuum electron devices in general. It covers the latest developments in field emission theory as well as new methods towards improving thermionic and cold cathodes. It addresses thermionic cathodes, such as oxide cathodes, impregnated and scandate cathodes, as well as photocathodes and field emitters – the latter comprising carbon nanotubes, graphene and Spindt-type emitter arrays. Despite the rise and fall of the once dominant types of vacuum tubes, such as radio valves and cathode ray tubes, cathodes are continually being improved upon as new applications with increased demands arise, for example in electron beam lithography, high-power and high-frequency microwave tubes, terahertz imaging and electron sources for accelerators. Written by 17 experts in the field, the book presents the latest developments in cathodes needed for these applications, discussing the state of the art and addressing future trends.

Download or read book Synthesis and Field Emission Properties of Carbon Nanotube Films written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, vertically aligned multiwalled carbon nanotube films were grown by microwave plasma chemical vapor deposition (MWCVD). Through controlling the thickness of the iron thin film, carbon nanotubes with different diameters were obtained. When the thickness of the iron layer was reduced to 0.3-0.5 nm, single-wall and double-wall nanotubes were obtained with a high areal density (~ 1012/cm2) and vertical alignment. Scanning electron microscopy, Raman spectroscopy and high resolution transmission electron microscopy were employed to characterize the as-deposited nanotubes. In addition, a systematic study of the internal structure transition of the carbon nanotubes has been conducted and a growth model was proposed in terms of carbon surface and bulk diffusion. The field emission of the carbon nanotube films has also been explored in this study. Different measurement systems including a variable distance field emission system, a field emission imaging system, and a field electron emission system (FEEM) were employed. The effects of the diameter (multi-wall vs single- and double- wall), the adsorbates, and the temperature on the field emission properties of carbon nanotubes have been exhibited. Finally, two processes including hydrogen plasma etching and re-growth were used to treat the as-deposited film, and an increased emission site density was observed for the re-grown carbon nanotube film.

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.

Download or read book Carbon Nanotube and Related Field Emitters written by Yahachi Saito and published by Wiley-VCH. This book was released on 2010-08-30 with total page 504 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.

Download or read book Field Emission Microscopy of Carbon Nanotube Fibers written by Taha Yasin Posos and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large-area field emission cathodes made from carbon nanotube (CNT) fiber have long been promising as the next generation electron sources for high-power radio frequency (rf) or microwave vacuum electronic devices (VEDs). CNTs have excellent field emission properties such as low turn-on voltage and high output current at electric fields as low as 8́ơ10 MV/m, as compared to the legacy metal emitter technology. Therefore, CNT technology has the potential to decrease the operating voltage and simplify VED systems. However, in addition to high beam charge, beam-driven radiation sources require electron beams with low emittance (i.e. high brightness), which must be provided in a stable continuous fashion. Although there have been many studies on CNT fibers' emission current performance, there is not sufficient research on their emission uniformity, emittance, brightness, and overall upper performance limitations specific to the CNT material itself. The lack of these important characterization metrics led to the work presented in this thesis. Not only were the conventional current-voltage (I-V) relations measured and evaluated, but also the electron beams carrying the currents were monitored ���� �������� in real-time by projecting the beam onto a scintillator screen in a custom field emission microscope. These enabled the measurement and evaluation of emittance and brightness. The existing bottlenecks limiting the fiber's performance were uncovered for the first time and new advanced CNT fiber cathode designs were proposed and engineered accordingly.In Ch.2, various standard (previously attempted) designs of CNT fiber cathodes were tested in the field emission microscope. The results showed that all cathodes had high emittance, low brightness, a large beam spread, non-uniform emission, current saturation, and instability. Hot spots and micro breakdowns were observed during emission. Analysis of the data revealed that all these problems were due to the formation of stray emitters on the cathode surface during emission. It was concluded that the tested fibers failed to provide any reasonable beam quality regardless of the cathode geometry.Exceptionally non-uniform current emission observed in the experiments raised the question about the mechanism of current saturation when the output charge failed to keep up with the increasing electric field. In Ch.3, a computational method was developed to extract the emission area from the emission micrographs and then calculate the emission current density. It was found that the current density saturated quickly and stopped obeying the Fowler-Nordheim law. It was demonstrated that the saturation effect occurred because the local current density reached a maximum level limited by the number of carriers and their finite transit time inside the bulk material's depletion region. It was concluded that overcoming the saturation issue is only possible if uniform emission can be achieved.In Ch.4, a brand new and unique cathode design was developed that successfully solved all the problems caused by stray emitters. It was demonstrated that the new design provided a uniform and stable electron beam with a small divergence angle, resulting in a beam with low emittance and high brightness. This result is a significant advancement that outlines a feasible path toward utilizing CNT fiber electron sources for practical VED applications. More specifically, it was observed that the entire cathode surface of a radius of approximately 75 ��m emitted uniformly (with no hot spots) in the direction of the applied electric field. From this, the normalized dc current brightness was estimated as ��N = 3.7 x 1010 A m2 rad2 using the estimated emittance of 52 nm rad. From this, the brightness in the pulsed mode, the preferable mode in most VED HPM applications, was predicted to attain a notable value of ��N = 4.4 x 1015 A m2 rad2.Equations not included.

Download or read book Technical Digest of the International Vacuum Nanoelectronics Conference written by and published by . This book was released on 2004 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.

Download or read book Advances in Imaging and Electron Physics written by Peter W. Hawkes and published by Elsevier. This book was released on 2007-08-22 with total page 285 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Imaging and Electron Physics merges two long-running serials-Advances in Electronics and Electron Physics and Advances in Optical and Electron Microscopy. This series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains.

Download or read book Carbon Nanotubes written by Mohammed Rahman and published by BoD – Books on Demand. This book was released on 2018-04-26 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book Carbon Nanotubes - Recent Progress contains a number of recent researches on synthesis, growth, characterization, development, and potential applications on carbon materials especially CNTs in nanoscale. It is a promising novel research from top to bottom that has received a lot of interest in the last few decades. It covers the advanced topics on the physical, chemical, and potential applications of CNTs. Here, the interesting reports on cutting-edge science and technology related to synthesis, morphology, control, hybridization, and prospective applications of CNTs are concluded. This potentially unique work offers various approaches on the R

Download or read book Vacuum Nanoelectronic Devices written by Anatoliy Evtukh and published by John Wiley & Sons. This book was released on 2016-03-16 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introducing up-to-date coverage of research in electron field emission from nanostructures, Vacuum Nanoelectronic Devices outlines the physics of quantum nanostructures, basic principles of electron field emission, and vacuum nanoelectronic devices operation, and offers as insight state-of-the-art and future researches and developments. This book also evaluates the results of research and development of novel quantum electron sources that will determine the future development of vacuum nanoelectronics. Further to this, the influence of quantum mechanical effects on high frequency vacuum nanoelectronic devices is also assessed. Key features: • In-depth description and analysis of the fundamentals of Quantum Electron effects in novel electron sources. • Comprehensive and up-to-date summary of the physics and technologies for THz sources for students of physical and engineering specialties and electronics engineers. • Unique coverage of quantum physical results for electron-field emission and novel electron sources with quantum effects, relevant for many applications such as electron microscopy, electron lithography, imaging and communication systems and signal processing. • New approaches for realization of electron sources with required and optimal parameters in electronic devices such as vacuum micro and nanoelectronics. This is an essential reference for researchers working in terahertz technology wanting to expand their knowledge of electron beam generation in vacuum and electron source quantum concepts. It is also valuable to advanced students in electronics engineering and physics who want to deepen their understanding of this topic. Ultimately, the progress of the quantum nanostructure theory and technology will promote the progress and development of electron sources as main part of vacuum macro-, micro- and nanoelectronics.

Download or read book Surface Science Tools for Nanomaterials Characterization written by Challa S.S.R. Kumar and published by Springer. This book was released on 2015-03-10 with total page 653 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fourth volume of a 40volume series on nano science and nanotechnology, edited by the renowned scientist Challa S.S.R. Kumar. This handbook gives a comprehensive overview about Surface Science Tools for Nanomaterials Characterization. Modern applications and state-of-the-art techniques are covered and make this volume an essential reading for research scientists in academia and industry.