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Vertically aligned carbon nanofibers (VACNFs) have found a variety of electronic applications. To further realize these applications, a good understanding of the charge transport properties is essential. In this work, charge transport properties have been systematically measured for three types of VACNF forests with Ni as catalyst, namely VACNFs grown by direct current PECVD, and inductively coupled PECVD at both normal pressure (3.6 Torr) and low pressure (50 mTorr). The structure and composition of these nanofibers have also been investigated in detail prior to the charge transport measurements. It has been found that the dc VACNF body consists of three parts: a 10-15 nm thick graphitic outer layer, cross-struts, and a layer with darker contrast in between. Carbon, nitrogen, silicon, nickel and oxygen are all present in the dc VACNF body. Ni is distributed along the entire dc VACNF body, as first reported in this work. Auger electron spectroscopy results indicate that Ni is primarily located in fiber walls, not in the center catalytic part. Four-probe I-V measurements on individual nanofibers have been enabled by the fabrication of multiple metal ohmic contacts on individual fibers that exhibited resistance of only a few k[Omega]. An O2 plasma reactive ion etch method has been used to achieve ohmic contacts between the nanofibers and Ti/Au, Ag/Au, Cd/Au, and Cr/Au electrodes. Dc VACNFs exhibit linear I-V behavior at room temperature, with a resistivity of approximately 4.2x10−3 [Omega]·cm. Gate effect is not observed when the heavily doped Si substrate is used as a back gate. Our measurements are consistent with a dominant transport mechanism of electrons traveling through intergraphitic planes in the dc VACNFs. The resistivity of these fibers is almost independent of temperature, and the contact resistance decreases as temperature increases. Further studies reveal that the 10-15 nm thick graphitic outer layer dominates the charge transport properties of dc VACNFs. This is demonstrated by comparison of charge transport properties of as-grown VACNFs and VACNFs with the outer layer partially removed by oxygen plasma reactive ion etch. The linear I-V behavior of the fibers does not vary as this outer layer becomes thinner, but displays a drastic shift to a rectifying behavior when this layer is completely stripped away from some regions of the nanofiber. This shift may be related with the compositional differences in the outer layer and the inner core of the nanofibers. Our results imply that by varying the extent of graphitization and structure of the outer layer, it may be possible to achieve controllable charge transport properties for dc VACNFs. VACNFs grown by inductively coupled PECVD at normal and low pressure both have a defective outer layer and a more crystalline inner core. The composition of these fibers is predominately carbon, and Ni is not observed along the fiber body. Nitrogen is present possibly as a result of sample storage in air. Two-probe charge transport measurements indicate linear I-V behavior, and the resistivity of both types of inductively coupled PECVD grown VACNFs is on the order of 10−3 to 10−4 [Omega]·cm.
This is the second volume in a series of books on selected topics in Nanoscale Science and Technology based on lectures given at the well-known INFN schools of the same name. The aim of this collection is to provide a reference corpus of suitable, introductory material to relevant subfields, as they mature over time, by gathering the significantly expanded and edited versions of tutorial lectures, given over the years by internationally known experts. The present set of notes stems in particular from the participation and dedication of prestigious lecturers, such as Andrzej Huczko, Nicola Pugno, Alexander Malesevic, Pasquale Onorato and Stefano Bellucci. All lectures were subsequently carefully edited and reworked, taking into account the extensive follow-up discussions. A tutorial lecture by Huczko et al. shows how a variety of carbon and ceramic nanostructures (nanotubes, nanowires, nanofibres, nanorods, and nanoencapsulates) have in particular great potential for improving our understanding of the fundamental concepts of the roles of both dimensionality and size on physical material properties . Bellucci and Onorato provide an extensive and tutorial review of the (quantum) transport properties in carbon nanotubes, encompassing a description of the electronic structure from graphene to single-wall nanotubes, as well as a discussion of experimental evidence of superconductivity in carbon nanotubes and the corresponding theoretical interpretation. In the first contribution by Pugno, new ideas on how to design futuristic self-cleaning, super-adhesive and releasable hierarchical smart materials are presented. He also reviews the mechanical strength of such nanotubes and megacables, with an eye to the visionary project of a carbon nanotube-based ‘space elevator megacable’. In his second contribution, Pugno outlines in detail the role on the fracture strength of thermodynamically unavoidable atomistic defects with different size and shape, both numerically and theoretically, for nanotubes and nanotube bundles. Focusing on graphitic allotropes, the chapter by Bellucci and Malesevic aims to give a taste of the widespread implications carbon nanostructures have on research and applications, starting from an historical overview, followed by a discussion of the structure and physical properties of carbon nanotubes and graphene, in particular in the context of the several different synthesis techniques presently available.
This book presents a comprehensive review of research on applications of carbon nanotubes (CNTs) and graphene to electronic devices. As nanocarbons in general, and CNTs and graphene in particular, are becoming increasingly recognized as the most promising materials for future generations of electronic devices, including transistors, sensors, and interconnects, a knowledge gap still exists between the basic science of nanocarbons and their feasibility for cost-effective product manufacturing. The book highlights some of the issues surrounding this missing link by providing a detailed review of the nanostructure and electronic properties, materials, and device fabrication and of the structure–property–application relationships.
Presenting the latest coverage of the fundamentals and applications of nanofibrous materials and their structures for graduate students and researchers, this book bridges the communication gap between fiber technologists and materials scientists and engineers. Featuring intensive coverage of electroactive, bioactive and structural nanofibers, it provides a comprehensive collection of processing conditions for electrospinning and includes recent advances in nanoparticle-/nanotube-based nanofibers. The book also covers mechanical properties of fibers and fibrous assemblies, as well as characterization methods.
Smart Composites: Mechanics and Design addresses the current progress in the mechanics and design of smart composites and multifunctional structures. Divided into three parts, it covers characterization of properties, analyses, and design of various advanced composite material systems with an emphasis on the coupled mechanical and non-mechanical behaviors. Part one includes analyses of smart materials related to electrically conductive, magnetostrictive nanocomposites and design of active fiber composites. These discussions include several techniques and challenges in manufacturing smart composites and characterizing coupled properties, as well as the analyses of composite structures at various length and time scales undergoing coupled mechanical and non-mechanical stimuli considering elastic, viscoelastic (and/or viscoplastic), fatigue, and damage behaviors. Part two is dedicated to a higher-scale analysis of smart structures with topics such as piezoelectrically actuated bistable composites, wing morphing design using macrofiber composites, and multifunctional layered composite beams. The analytical expressions for characterization of the smart structures are presented with an attention to practical application. Finally, part three presents recent advances regarding sensing and structural health monitoring with a focus on how the sensing abilities can be integrated within the material and provide continuous sensing, recognizing that multifunctional materials can be designed to both improve and enhance the health-monitoring capabilities and also enable effective nondestructive evaluation. Smart Composites: Mechanics and Design is an essential text for those interested in materials that not only possess the classical properties of stiffness and strength, but also act as actuators under a variety of external stimuli, provide passive and active response to enable structural health monitoring, facilitate advanced nondestructive testing strategies, and enable shape-changing and morphing structures.
“There’s Plenty of Room at the Bottom” ⎯ this was the title of the lecture Prof. Richard Feynman delivered at California Institute of Technology on December 29, 1959 at the American Physical Society meeting. He considered the possibility to manipulate matter on an atomic scale. Indeed, the design and controllable synthesis of nanomaterials have attracted much attention because of their distinctive geometries and novel physical and chemical properties. For the last two decades nano-scaled materials in the form of nanofibers, nanoparticles, nanotubes, nanoclays, nanorods, nanodisks, nanoribbons, nanowhiskers etc. have been investigated with increased interest due to their enormous advantages, such as large surface area and active surface sites. Among all nanostructures, nanofibers have attracted tremendous interest in nanotechnology and biomedical engineering owing to the ease of controllable production processes, low pore size and superior mechanical properties for a range of applications in diverse areas such as catalysis, sensors, medicine, pharmacy, drug delivery, tissue engineering, filtration, textile, adhesive, aerospace, capacitors, transistors, battery separators, energy storage, fuel cells, information technology, photonic structures and flat panel displays, just to mention a few. Nanofibers are continuous filaments of generally less than about 1000 nm diameters. Nanofibers of a variety of cellulose and non-cellulose based materials can be produced by a variety of techniques such as phase separation, self assembly, drawing, melt fibrillation, template synthesis, electro-spinning, and solution spinning. They reduce the handling problems mostly associated with the nanoparticles. Nanoparticles can agglomerate and form clusters, whereas nanofibers form a mesh that stays intact even after regeneration. The present book is a result of contributions of experts from international scientific community working in different areas and types of nanofibers. The book thoroughly covers latest topics on different varieties of nanofibers. It provides an up-to-date insightful coverage to the synthesis, characterization, functional properties and potential device applications of nanofibers in specialized areas. We hope that this book will prove to be timely and thought provoking and will serve as a valuable reference for researchers working in different areas of nanofibers. Special thanks goes to the authors for their valuable contributions.
This handbook provides the most comprehensive, up-to-date and easy-to-apply information on the physics, mechanics, reliability and packaging of micro- and opto-electronic materials. It details their assemblies, structures and systems, and each chapter contains a summary of the state-of-the-art in a particular field. The book provides practical recommendations on how to apply current knowledge and technology to design and manufacture. It further describes how to operate a viable, reliable and cost-effective electronic component or photonic device, and how to make such a device into a successful commercial product.
Micro and Nano Systems for Biophysical Studies of Cells and Small Organisms provides a comprehensive introduction to the state-of-the-art micro and nano systems that have recently been developed and applied to biophysical studies of cells and small organisms. These micro and nano systems span from microelectromechanical systems (MEMS) and microfluidic devices to robotic micro-nanomanipulation systems. These biophysical studies range from cell mechanics to the neural science of worms and Drosophila. This book will help readers understand the fundamentals surrounding the development of these tools and teach them the most recent advances in cellular and organismal biophysics enabled by these technologies. Comprehensive coverage of micro and nano-system technology and application to biophysical studies of cells and small organisms. Highlights the most recent advances in cellular and organismal biophysics enabled by micro and nano systems. Insightful outlook on future directions and trends in each chapter covering a sub-area of the book topic.