This book brings together the most up-to-date information on the fabrication techniques, properties, and potential applications of low dimensional silicon carbide (SiC) nanostructures such as nanocrystallites, nanowires, nanotubes, and nanostructured films. It also summarizes the tremendous achievements acquired during the past three decades involving structural, electronic, and optical properties of bulk silicon carbide crystals. SiC nanostructures exhibit a range of fascinating and industrially important properties, such as diverse polytypes, stability of interband and defect-related green to blue luminescence, inertness to chemical surroundings, and good biocompatibility. These properties have generated an increasing interest in the materials, which have great potential in a variety of applications across the fields of nanoelectronics, optoelectronics, electron field emission, sensing, quantum information, energy conversion and storage, biomedical engineering, and medicine. SiC is also a most promising substitute for silicon in high power, high temperature, and high frequency microelectronic devices. Recent breakthrough pertaining to the synthesis of ultra-high quality SiC single-crystals will bring the materials closer to real applications. Silicon Carbide Nanostructures: Fabrication, Structure, and Properties provides a unique reference book for researchers and graduate students in this emerging field. It is intended for materials scientists, physicists, chemists, and engineers in microelectronics, optoelectronics, and biomedical engineering.

Recently, carbon nanosheets (CNS), a novel nanostructure, were developed in our laboratory as a field emission source for high emission current. To characterize, understand and improve the field emission properties of CNS, a ultra-high vacuum surface analysis system was customized to conduct relevant experimental research in four distinct areas. The system includes Auger electron spectroscopy (AES), field emission energy spectroscopy (FEES), field emission I-V testing, and thermal desorption spectroscopy (TDS). Firstly, commercial Mo single tips were studied to calibrate the customized system. AES and FEES experiments indicate that a pyramidal nanotip of Ca and O elements formed on the Mo tip surface by field induced surface diffusion. Secondly, field emission I-V testing on CNS indicates that the field emission properties of pristine nanosheets are impacted by adsorbates. For instance, in pristine samples, field emission sources can be built up instantaneously and be characterized by prominent noise levels and significant current variations. However, when CNS are processed via conditioning (run at high current), their emission properties are greatly improved and stabilized. Furthermore, only H2 desorbed from the conditioned CNS, which indicates that only H adsorbates affect emission. Thirdly, the TDS study on nanosheets revealed that the predominant locations of H residing in CNS are sp2 hybridized C on surface and bulk. Fourthly, a fabricating process was developed to coat low work function ZrC on nanosheets for field emission enhancement. The carbide triple-peak in the AES spectra indicated that Zr carbide formed, but oxygen was not completely removed. The Zr(CxOy) coating was dispersed as nanobeads on the CNS surface. Although the work function was reduced, the coated CNS emission properties were not improved due to an increased beta factor. Further analysis suggest that for low emission current (10 uA), thermal, ionic or electronic transition effects may occur, which differently affect the field emission process.

This book provides information on synthesis, properties, and applications of carbon nanomaterials. With novel materials, such as graphene (atomically flat carbon) or carbon onions (carbon nanospheres), the family of carbon nanomaterials is rapidly growing. This book provides a state-of-the-art overview and in-depth analysis of the most important ca

This monograph solely presents the Fowler-Nordheim field emission (FNFE) from semiconductors and their nanostructures. The materials considered are quantum confined non-linear optical, III-V, II-VI, Ge, Te, carbon nanotubes, PtSb2, stressed materials, Bismuth, GaP, Gallium Antimonide, II-V, Bi2Te3, III-V, II-VI, IV-VI and HgTe/CdTe superlattices with graded interfaces and effective mass superlattices under magnetic quantization and quantum wires of the aforementioned superlattices. The FNFE in opto-electronic materials and their quantum confined counterparts is studied in the presence of light waves and intense electric fields on the basis of newly formulated electron dispersion laws that control the studies of such quantum effect devices. The importance of band gap measurements in opto-electronic materials in the presence of external fields is discussed from this perspective. This monograph contains 200 open research problems which form the very core and are useful for Ph. D students and researchers. The book can also serve as a basis for a graduate course on field emission from solids.

More than 50% of the total energy produced is typically rejected in the form of waste heat from various processes. The grand challenge is that most of this waste heat is released at temperatures much lower than 1000 C, which makes it difficult to recover it using traditional methods which require higher operating temperatures for thermal energy conversion. In addition, these traditional methods involve different intermediate processes and do not offer direct conversion into electricity. In this regard, thermal energy conversion through thermionic emission can offer direct conversion of waste heat into electricity with highest theoretical efficiency. So, waste heat recovery through thermionic emission energy conversion is of great interest and is the motivation for the present work. However the greatest challenge involves the discovery or availability of the material with appropriate work functions and stability criteria. To address the need for developing suitable materials toward thermionic energy conversion, we investigated phosphorus doping in individual diamond nanocrystals, conical carbon nanostructures (CCNTs) and diamond nanocrystals supported on conical carbon nanostructures. Hybrid architectures, diamond nanocrystals supported on high aspect ratio structures will allow the study of true performance of nanocrystals free from grain boundaries and also offer field enhancements. First, the synthesis of CCNTs over large area and flat substrates is investigated. From the experimental results, we successfully synthesized CCNTs on planar graphite and tungsten foil substrates with areas as large as (>0.5 cm2). A detailed underlying nucleation and growth mechanism was also demonstrated supported with regrowth experiments and kinetic growth model. Secondly, selective nucleation of the diamond crystals on the tips or complete coating on CCNTs was demonstrated and a likely mechanism for the nucleation and growth of diamond crystals is also presented. Thirdly, the field and thermionic emission characteristics from the as synthesized CCNTs have shown to exhibit enhanced emission characteristics such as low turn-on voltages, large field enhancement factor and lower work function values owing to their higher aspect ratios and optimum density overcoming field screening effects. Finally, phosphorus doping into these individual diamond crystals and diamond films was performed and thermionic emission characteristics were studied. Work function values as low as 1.8 eV from diamond films and 2.2 eV from diamond crystals was obtained. In summary, the main outcomes of this work include growth of large area CCNTs on flat substrates, discovery of the enhanced field and thermionic emission characteristics of CCNTs, selective nucleation and phosphorus doping of individual diamond nanocrystals on CCNTs free from grain boundaries and work function value as low as 2.2 eV from thermionic emission from these crystals.

Proceedings of the NATO Advanced Study Institute, Erice, Sicily, Italy, July 19-31, 2000

Defects in Nanocrystals: Structural and Physico-Chemical Aspects discusses the nature of semiconductor systems and the effect of the size and shape on their thermodynamic and optoelectronic properties at the mesoscopic and nanoscopic levels. The nanostructures considered in this book are individual nanometric crystallites, nanocrystalline films, and nanowires of which the thermodynamic, structural, and optical properties are discussed in detail. The work: Outlines the influence of growth processes on their morphology and structure Describes the benefits of optical spectroscopies in the understanding of the role and nature of defects in nanostructured semiconductors Considers the limits of nanothermodynamics Details the critical role of interfaces in nanostructural behavior Covers the importance of embedding media in the physico-chemical properties of nanostructured semiconductors Explains the negligible role of core point defects vs. surface and interface defects Written for researchers, engineers, and those working in the physical and physicochemical sciences, this work comprehensively details the chemical, structural, and optical properties of semiconductor nanostructures for the development of more powerful and efficient devices.

New Frontiers in Nanochemistry: Concepts, Theories, and Trends, Volume 2: Topological Nanochemistry is the second of the new three-volume set that explains and explores the important basic and advanced modern concepts in multidisciplinary chemistry. Under the broad expertise of the editor, this second volume explores the rich research areas of nanochemistry with a specific focus on the design and control of nanotechnology by structural and reactive topology. The objective of this particular volume is to emphasize the application of nanochemistry. With 46 entries from eminent international scientists and scholars, the content in this volume spans concepts from A-to-Z—from entries on the atom-bond connectivity index to the Zagreb indices, from connectivity to vapor phase epitaxy, and from fullerenes to topological reactivity—and much more. The definitions within the text are accompanied by brief but comprehensive explicative essays as well as figures, tables, etc., providing a holistic understanding of the concepts presented.