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Empirical Investigation Of Carbon Nanotube Pillar Array Field Emitter Geometry For Increased Current Densities
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Book Synopsis Empirical Investigation of Carbon Nanotube Pillar Array Field Emitter Geometry for Increased Current Densities by : Jeremy Lucas Silan
Download or read book Empirical Investigation of Carbon Nanotube Pillar Array Field Emitter Geometry for Increased Current Densities written by Jeremy Lucas Silan and published by . This book was released on 2011 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Field Emission Properties of Carbon Nanotube Pillar Arrays Patterned Directly on Metal Alloy Surfaces by :
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.
Book Synopsis Gated Carbon Nanotube Pillar Arrays for High Current Applications by :
Download or read book Gated Carbon Nanotube Pillar Arrays for High Current Applications 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 nanotubes (CNTs) are attractive electron sources because of their mechanical stability, high electrical conductivity, and low turn-on fields. These properties make CNTs attractive candidates for a number of possible applications, in particular, those requiring high current densities such as travelling wave tube amplifiers and electric propulsion systems. In addition to high emission current density, a generally desirable operational parameter of cathodes is low electron extraction voltage. This is achievable with an array of emitters in which each of the emitters is fabricated with its own extracting electrode at a close distance. This concept has been previously developed for microfabricated Si cathodes. Similar cathode structures have been investigated for carbon nanostructure emitters, however, a number of challenges have been insurmountable, namely the inability to fabricate an individual CNT array in a controlled manner. This limitation has hindered the success of such cathode structures. To address this issue, in this work, we will introduce an integrated gated array of controlled CNT cathodes based on our previously demonstrated, highly stable carbon nanotube pillar array. A detailed fabrication process for this cathode structure will also be presented.
Book Synopsis Fabrication, Field Emission Properties and Theoretical Simulation of Triode-type Carbon Nanotube Emitter Arrays by : Jianfeng Wu
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.
Book Synopsis Characterization of Carbon Nanotube Based Thin Film Field Emitter by : Niraj Sinha
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.
Book Synopsis Enhanced Field Emission Properties from Carbon Nanotube Emitters Grown on NiCr Alloy Surfaces with Grain Boundary Effect by :
Download or read book Enhanced Field Emission Properties from Carbon Nanotube Emitters Grown on NiCr Alloy Surfaces with Grain Boundary Effect 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 nanotubes (CNTs) are known to have exceptional field emission properties such as low turn-on voltage and high current density. Nilsson et al. reported that field emission properties depend highly on the density of the CNT films. The CNTs must have low density in order to minimize electrostatic field screening from neighboring nanotubes. At the same time, the CNT films must have a high number of emitting sites to achieve a desirable current density. Recently, the direct growth of CNTs on metal alloys containing Ni, Cr, and Fe has been shown to be an attractive alternative for fabrication of CNT emitters without requiring a metal catalyst deposition step. Herein, we report the field emission properties of multi-walled carbon nanotube (MWNT) films grown on polished smooth 80/20 and 70/30 NiCr surfaces by thermal chemical vapor deposition. We show that 80/20 NiCr surfaces prohibit growth of MWNTs at the grain boundaries resulting in a lower turn-on field in comparison to a continuous MWNT film obtained with 70/30 NiCr substrates.
Book Synopsis Carbon Nanotubes by : Michael J. O’Connell
Download or read book Carbon Nanotubes written by Michael J. O’Connell and published by CRC Press. This book was released on 2018-10-03 with total page 339 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since their discovery more than a decade ago, carbon nanotubes (CNTs) have held scientists and engineers in captive fascination, seated on the verge of enormous breakthroughs in areas such as medicine, electronics, and materials science, to name but a few. Taking a broad look at CNTs and the tools used to study them, Carbon Nanotubes: Properties and Applications comprises the efforts of leading nanotube researchers led by Michael O’Connell, protégé of the late father of nanotechnology, Richard Smalley. Each chapter is a self-contained treatise on various aspects of CNT synthesis, characterization, modification, and applications. The book opens with a general introduction to the basic characteristics and the history of CNTs, followed by discussions on synthesis methods and the growth of “peapod” structures. Coverage then moves to electronic properties and band structures of single-wall nanotubes (SWNTs), magnetic properties, Raman spectroscopy of electronic and chemical behavior, and electromechanical properties and applications in NEMS (nanoelectromechanical systems). Turning to applications, the final sections of the book explore mechanical properties of SWNTs spun into fibers, sidewall functionalization in composites, and using SWNTs as tips for scanning probe microscopes. Taking a fresh look at this burgeoning field, Carbon Nanotubes: Properties and Applications points the way toward making CNTs commercially viable.
Download or read book Carbon Nanotubes written by M. Meyyappan and published by CRC Press. This book was released on 2004-07-28 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes, with their extraordinary mechanical and unique electronic properties, have garnered much attention in the past five years. With a broad range of potential applications including nanoelectronics, composites, chemical sensors, biosensors, microscopy, nanoelectromechanical systems, and many more, the scientific community is more moti
Download or read book Carbon Nanotubes written by M. Endo and published by Elsevier. This book was released on 2013-10-22 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes have been studied extensively in relation to fullerenes, and together with fullerenes have opened a new science and technology field on nano scale materials. A whole range of issues from the preparation, structure, properties and observation of quantum effects in carbon nanotubes in comparison with 0-D fullerenes are discussed. In addition, complementary reviews on carbon nanoparticles such as carbon nano-capsules, onion-like graphite particles and metal-coated fullerenes are covered. This book aims to cover recent research and development in this area, and so provide a convenient reference tool for all researchers in this field. It is also hoped that this book can serve to stimulate future work on carbon nanotubes.
Book Synopsis Springer Handbook of Nanomaterials by : Robert Vajtai
Download or read book Springer Handbook of Nanomaterials written by Robert Vajtai and published by Springer Science & Business Media. This book was released on 2013-08-20 with total page 1234 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Springer Handbook of Nanomaterials covers the description of materials which have dimension on the "nanoscale". The description of the nanomaterials in this Handbook follows the thorough but concise explanation of the synergy of structure, properties, processing and applications of the given material. The Handbook mainly describes materials in their solid phase; exceptions might be e.g. small sized liquid aerosols or gas bubbles in liquids. The materials are organized by their dimensionality. Zero dimensional structures collect clusters, nanoparticles and quantum dots, one dimensional are nanowires and nanotubes, while two dimensional are represented by thin films and surfaces. The chapters in these larger topics are written on a specific materials and dimensionality combination, e.g. ceramic nanowires. Chapters are authored by well-established and well-known scientists of the particular field. They have measurable part of publications and an important role in establishing new knowledge of the particular field.
Book Synopsis Mechanics of Carbon Nanotubes by : Vasyl Harik
Download or read book Mechanics of Carbon Nanotubes written by Vasyl Harik and published by Academic Press. This book was released on 2018-07-27 with total page 327 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanics of Carbon Nanotubes: Fundamentals, Modeling and Safety draws on the latest academic research and nanotechnology applications to provide a comprehensive guide on the most recent developments in the science of carbon nanotubes. The fundamentals of nanomechanics and mechanical behavior of carbon nanotubes are presented in initial chapters, followed by more advanced topics such as the classification of carbon nanotubes, carbon nanotubes in nanocomposites, multiwall carbon nanotubes, and recent trends.This book provides a system for the classification of carbon nanotubes into 20 classes, aiding correct selection for various applications, and includes the Atomic Registry Matrix Analysis for nanoscale interfaces, essential for design involving friction or sliding. Parametric maps are included to help readers pick the correct model for a particular CNT geometry, in addition to a thorough examination of the effective thickness paradox and safety issues related to CNTs, such as toxicity at high aspect ratio.Mechanics of Carbon Nanotubes is essential reading for anyone involved in research or engineering that includes carbon nanotubes, be they students or seasoned professionals in the field. It is particularly useful to those working with applications in the areas of microelectronics, robotics, aerospace, composites, or prosthetics. Provides a system for the classification of carbon nanotubes, aiding correct selection for various applications Includes the Matrix Registry Analysis for nanoscale interfaces that is essential for design involving friction or sliding Features parametric maps to help readers pick the right model for a particular CNT geometry (beam vs. shell vs. thin or thick shells, etc.) Presents a thorough examination of the safety issues related to CNTs, including toxicity at high aspect ratio
Book Synopsis Nanomaterials for Drug Delivery and Therapy by : Alexandru Mihai Grumezescu
Download or read book Nanomaterials for Drug Delivery and Therapy written by Alexandru Mihai Grumezescu and published by William Andrew. This book was released on 2019-03-14 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanomaterials for Drug Delivery and Therapy presents recent advances in the field of nanobiomaterials and their important applications in drug delivery, therapy and engineering. The book offers pharmaceutical perspectives, exploring the development of nanobiomaterials and their interaction with the human body. Chapters show how nanomaterials are used in treatments, including neurology, dentistry and cancer therapy. Authored by a range of contributors from global institutions, this book offers a broad, international perspective on how nanotechnology-based advances are leading to novel drug delivery and treatment solutions. It is a valuable research resource that will help both practicing medics and researchers in pharmaceutical science and nanomedicine learn more on how nanotechnology is improving treatments. Assesses the opportunities and challenges of nanotechnology-based drug delivery systems Explores how nanotechnology is being used to create more efficient drug delivery systems Discusses which nanomaterials make the best drug carriers
Book Synopsis Triboelectric Nanogenerators by : Zhong Lin Wang
Download or read book Triboelectric Nanogenerators written by Zhong Lin Wang and published by Springer. This book was released on 2016-08-17 with total page 537 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces an innovative and high-efficiency technology for mechanical energy harvesting. The book covers the history and development of triboelectric nanogenerators, basic structures, working principles, performance characterization, and potential applications. It is divided into three parts: Part A illustrates the fundamental working modes of triboelectric nanogenerators with their prototype structures and theoretical analysis; Part B and Part C introduce two categories of applications, namely self-powered systems and self-powered active sensors. The book will be an ideal guide to scientists and engineers beginning to study triboelectric nanogenerators or wishing to deepen their knowledge of the field. Readers will be able to place the technical details about this technology in context, and acquire the necessary skills to reproduce the experimental setups for fabrication and measurement.
Book Synopsis Physical Properties Of Carbon Nanotubes by : G Dresselhaus
Download or read book Physical Properties Of Carbon Nanotubes written by G Dresselhaus and published by World Scientific. This book was released on 1998-07-22 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an introductory textbook for graduate students and researchers from various fields of science who wish to learn about carbon nanotubes. The field is still at an early stage, and progress continues at a rapid rate. This book focuses on the basic principles behind the physical properties and gives the background necessary to understand the recent developments. Some useful computational source codes which generate coordinates for carbon nanotubes are also included in the appendix.
Book Synopsis Nanomaterials Chemistry by : C. N. R. Rao
Download or read book Nanomaterials Chemistry written by C. N. R. Rao and published by John Wiley & Sons. This book was released on 2007-09-24 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: With this handbook, the distinguished team of editors has combined the expertise of leading nanomaterials scientists to provide the latest overview of this field. They cover the whole spectrum of nanomaterials, ranging from theory, synthesis, properties, characterization to application, including such new developments as quantum dots, nanoparticles, nanoporous materials, nanowires, nanotubes, and nanostructured polymers. The result is recommended reading for everybody working in nanoscience: Newcomers to the field can acquaint themselves with this exciting subject, while specialists will find answers to all their questions as well as helpful suggestions for further research.
Book Synopsis Inorganic Nanowires by : M. Meyyappan
Download or read book Inorganic Nanowires written by M. Meyyappan and published by CRC Press. This book was released on 2018-09-03 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in nanofabrication, characterization tools, and the drive to commercialize nanotechnology products have contributed to the significant increase in research on inorganic nanowires (INWs). Yet few if any books provide the necessary comprehensive and coherent account of this important evolution. Presenting essential information on both popular and emerging varieties, Inorganic Nanowires: Applications, Properties, and Characterization addresses the growth, characterization, and properties of nanowires. Author Meyyappan is the director and senior scientist at Ames Center for Nanotechnology and a renowned leader in nanoscience and technology, and Sunkara is also a major contributor to nanowire literature. Their cutting-edge work is the basis for much of the current understanding in the area of nanowires, and this book offers an in-depth overview of various types of nanowires, including semiconducting, metallic, and oxide varieties. It also includes extensive coverage of applications that use INWs and those with great potential in electronics, optoelectronics, field emission, thermoelectric devices, and sensors. This invaluable reference: Traces the evolution of nanotechnology and classifies nanomaterials Describes nanowires and their potential applications to illustrate connectivity and continuity Discusses growth techniques, at both laboratory and commercial scales Evaluates the most important aspects of classical thermodynamics associated with the nucleation and growth of nanowires Details the development of silicon, germanium, gallium arsenide, and other materials in the form of nanowires used in electronics applications Explores the physical, electronic and other properties of nanowires The explosion of nanotechnology research activities for various applications is due in large part to the advances in the growth of nanowires. Continued development of novel nanostructured materials is essential to the success of so many economic sectors, ranging from computing and communications to transportation and medicine. This volume discusses how and why nanowires are ideal candidates to replace bulk and thin film materials. It covers the principles behind device operation and then adds a detailed assessment of nanowire fabrication, performance results, and future prospects and challenges, making this book a valuable resource for scientists and engineers in just about any field. Co-author Meyya Meyyappan will receive the Pioneer Award in Nanotechnology from the IEEE Nanotechnology Council at the IEEE Nano Conference in Portland, Oregon in August, 2011
Book Synopsis Physical and Chemical Properties of Carbon Nanotubes by : Satoru Suzuki
Download or read book Physical and Chemical Properties of Carbon Nanotubes written by Satoru Suzuki and published by . This book was released on 2013 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes are rolled up graphene sheets with a quasi-one-dimensional structure of nanometer-scale diameter. In these last twenty years, carbon nanotubes have attracted much attention from physicists, chemists, material scientists, and electronic device engineers because of their excellent structural, electronic, optical, chemical and mechanical properties. Carbon nanotube research, especially that aiming at industrial applications, is becoming more important. This book covers recent research topics regarding the physical, structural, chemical and electric properties on carbon nanotubes. All chapters were written by researchers who are active on the front lines. The chapters in this book will be helpful to many students, engineers and researchers working in the field of carbon nanotubes.
