Download or read book Characterization of Planar Defects in Silicon Carbide Nanowires written by Monika Katarzyna Wieligor and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Stacking faults and twins were identifying in SiC nanowires produced according three different synthesis methods. By direct observation of high resolution TEM images, analysis of Raman spectra, and from X-ray diffraction results we concluded that planar defects were present in all specimens, regardless the synthesis method. The study of TEM images revealed that concentration of defects was not uniform. The amount of stacking faults and twins varied between the samples, and seems to be dependent on the size of nanowires. Concentration of twins appeared to be highest in nanowires obtained from raw carbon blacks of small diameters. The quantitative analysis of concentration of defects was not conducted because Raman and conventional X-ray cannot discern stacking faults and twins. Therefore, the estimation of concentration of planar defects was based on the examination of TEM images. The application of two TEM modes, bright field and dark field, let to deduce that twins played a dominant role in observed defects. A minimum surface energy and strain energy argument was proposed to explain the formation of twins in the SiC nanowires. The high pressure measurements in DAC were performed and the results validated the core-shell model. The application of new carbon precursor revealed with new, highly efficient method of synthesis of SiC nanowires. We proved that it is possible to produce low-cost, catalyst-free, and high-yield SiC nanowires of 10 nm diameter and narrow size distribution. Morphology of the nanowires depended on carbon precursor used. That technique was described in details in Chapter IV. The model of typical nanowire, composed of crystalline SiC core, coated by thin, 2 nm amorphous SiC layer, was presented. After analysis of produced SiC nanowires we were able to construct the possible model of growth mechanism, and explain the differences in dimensions and morphology for nanowires, obtained from graphitized and not graphitized carbon blacks precursors. We deduced that vapor-solid growth mechanism is more plausible in nanowires synthesis from carbon black, than the vapor-liquid-solid mechanism"--Abstract.
Download or read book Characterization of Planar Defects in SiC Nanowires written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Stacking faults and twins were identifying in SiC nanowires produced according three different synthesis methods. By direct observation of high resolution TEM images, analysis of Raman spectra, and from X-ray diffraction results we concluded that planar defects were present in all specimens, regardless the synthesis method. The study of TEM images revealed that concentration of defects was not uniform. The amount of stacking faults and twins varied between the samples, and seems to be dependent on the size of nanowires. Concentration of twins appeared to be highest in nanowires obtained from raw carbon blacks of small diameters. The quantitative analysis of concentration of defects was not conducted because Raman and conventional X-ray cannot discern stacking faults and twins. Therefore, the estimation of concentration of planar defects was based on the examination of TEM images. The application of two TEM modes, bright field and dark field, let to deduce that twins played a dominant role in observed defects. A minimum surface energy and strain energy argument was proposed to explain the formation of twins in the SiC nanowires. The high pressure measurements in DAC were performed and the results validated the core-shell model. The application of new carbon precursor revealed with new, highly efficient method of synthesis of SiC nanowires. We proved that it is possible to produce low-cost, catalyst-free, and high-yield SiC nanowires of 10 nm diameter and narrow size distribution. Morphology of the nanowires depended on carbon precursor used. That technique was described in details in Chapter IV. The model of typical nanowire, composed of crystalline SiC core, coated by thin, 2 nm amorphous SiC layer, was presented. After analysis of produced SiC nanowires we were able to construct the possible model of growth mechanism, and explain the differences in dimensions and morphology for nanowires, obtained from graphitized and not graphitized carbon blacks precursors. We de.
Download or read book Production and Characterization of Nanostructured Silicon Carbide written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanostructured materials continue to attract attention because of their new and interesting properties, which are very different from their macrostructured equivalents. Since the size of grain and surface differs, a better understanding of the microstructure, the mechanism of formation, and methods of controlling surface properties is necessary. In this study, nanostructured silicon carbide has been produced from the solid-solid reaction of a mixture of silicon nanopowder and carbon multiwalled nanotubes (MWNT) sintered by induction. A study of the reaction rate at different temperatures has yielded a value for the activation energy of 254 " 36 kJ/mol, and has led to the conclusion that the reaction is diffusion-controlled. A second method produced pure silicon carbide nanowires using a procedure which kept the solid reactants, silicon powder and MWNT, separated while sintering at a constant temperature of 1200̆%. Silicon in the vapor-phase reacted at the surface of the MWNTs followed by diffusion of both precursors through the product phase boundary. The reaction time was varied, and a morphological study has been done describing changes in shape and size as a function of time. The initial reaction produced a layer of SiC providing the outer shell of coaxial structures with carbon nanotubes inside. As Si and C diffused through the product phase to react at the interface, the tube became filled with SiC to form solid SiC nanowires, and the outer diameter of the nanowires grew continuously as reaction time increased. After long sintering times, growth continued in two dimensions, fusing nanowires together into planar structures. In addition, the precursor form of carbon was varied, and nanowires produced by two different types of nanotubes have been studied. The produced SiC nanowires show cubic crystal structure. After a few hours of sintering, stacking faults began to occur inside the wires, and the frequency of occurrence of the stacking faults increased as reacti.
Download or read book Silicon Carbide Nanowires written by Ryan Michael Rich and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A highly reproducible method of producing SiC nanowires on a large scale is presented, and the average size of SiC nanowires was 30 nm. XRD revealed that the molar yield increased linearly with time. TEM showed a distribution of nanowire sizes that shifted towards larger diameters as sintering time increased. It is known that vapor-liquid-solid reactions involving a metal catalyst play a role in their formation, and there is further evidence that a vapor-solid mechanism contributes as well. The elastic properties of the following SiC morphologies were explored with pressure applied via a diamond anvil cell: 20 nm grains, 50 nm grains, 130 nm grains, and 30 nm nanowires The bulk modulus of nanowires increased by 8%, while that of 20 nm grains increased 30% in comparison to bulk material. The increased bulk modulus is explained by the core-shell model, where nanoparticles possess one or more distinct regions near the surface with identical crystal symmetry but different interatomic distances. Defects may also affect the bulk modulus, especially in the heavily faulted nanowires. As seen by TEM, planar faults were abundant, and their quantity decreased with decreasing diameter. The extended Convolutional Multiple Whole Profile (eCMWP) analysis was employed to quantitate the defects by XRD. This analysis concluded that twins are the most frequently occurring planar fault with a 2.20% probability of formation, which corresponds to a defect spacing of 38 nm. SiC nanowires are formed with an amorphous outer layer a few nanometers deep. It was concluded that the layer consisted mainly of amorphous SiC, but EDS confirmed that this structure was rich in oxygen. FTIR confirmed the presence of Si-O bands which increased in population with thermal treatment. The surface of SiC nanowires was modified by etching in HF and HNO3 acids. Silica bands were reduced and functional groups appeared after treatment. XRD found that grain size increased by 186% and dislocations decreased by 91% with treatment by nitric acid. It is proposed that modification of the surface leads to a reduction of surface stresses, thereby increasing the apparent grain size and reducing dislocations.
Download or read book Growth and Characterization of Silicon Carbide Thin Films and Nanowires written by Lunet Estefany Luna and published by . This book was released on 2016 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicon carbide (SiC) based electronics and sensors hold promise for pushing past the limits of current technology to achieve small, durable devices that can function in high-temperature, high-voltage, corrosive, and biological environments. SiC is an ideal material for such conditions due to its high mechanical strength, excellent chemical stability, and its biocompatibility. Consequently, SiC thin films and nanowires have attracted interest in applications such as micro- and nano-electromechanical systems, biological sensors, field emission cathodes, and energy storage devices. In terms of high-temperature microdevices, maintaining low-resistance electrical contact between metal and SiC remains a challenge. Although SiC itself maintains structural and electrical stability at high temperatures, the metallization schemes on SiC can suffer from silicide formation and oxidation when exposed to air. The second chapter presents efforts to develop stable metallization schemes to SiC. A stack consisting of Ni-induced solid-state graphitization of SiC and an atomic layer deposited layer of alumina is shown to yield low contact resistivity of Pt/Ti to polycrystalline n-type 3C-SiC films that is stable in air at 450 oC for 500 hours. The subsequent chapters focus on the growth and structural characterization of SiC nanowires. In addition to its structural stability in harsh-environments, there is interest in controlling SiC crystal structure or polytype formation. Over 200 different polytypes have been reported for SiC, with the most common being 3C, 4H, and 2H. In terms of SiC nanowire growth, the 3C or cubic phase is the most prevalent. However, as the stacking fault energy for SiC is on the order of a few meV, it is common to have a high density of stacking faults within a given SiC crystal structure. Thus, to enable reliable performance of SiC nanowires, a growth method that can promote a specific polytype or reduce stacking faults is of importance. Ni-catalyzed chemical vapor deposition method is employed for the growth of the nanowires. The effects of substrate structure and quality as well as the various growth parameters such as temperature, pressure, and post-deposition annealing are investigated. Most significant has been the growth and characterization of vertically aligned hexagonal phase (or 4H-like) SiC nanowires grown on commercially available 4H-SiC (0001). The studies presented in this thesis tackle issues in SiC metallization and nanowire growth in efforts to expand the versatility of SiC as a material platform for novel devices.
Download or read book Silicon Carbide written by Wolfgang J. Choyke and published by Springer Science & Business Media. This book was released on 2003-10-08 with total page 938 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the 1997 publication of "Silicon Carbide - A Review of Fundamental Questions and Applications to Current Device Technology" edited by Choyke, et al., there has been impressive progress in both the fundamental and developmental aspects of the SiC field. So there is a growing need to update the scientific community on the important events in research and development since then. The editors have again gathered an outstanding team of the world's leading SiC researchers and design engineers to write on the most recent developments in SiC.
Download or read book Silicon Carbide written by Peter Friedrichs and published by John Wiley & Sons. This book was released on 2011-04-08 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book prestigiously covers our current understanding of SiC as a semiconductor material in electronics. Its physical properties make it more promising for high-powered devices than silicon. The volume is devoted to the material and covers methods of epitaxial and bulk growth. Identification and characterization of defects is discussed in detail. The contributions help the reader to develop a deeper understanding of defects by combining theoretical and experimental approaches. Apart from applications in power electronics, sensors, and NEMS, SiC has recently gained new interest as a substrate material for the manufacture of controlled graphene. SiC and graphene research is oriented towards end markets and has high impact on areas of rapidly growing interest like electric vehicles. The list of contributors reads like a "Who's Who" of the SiC community, strongly benefiting from collaborations between research institutions and enterprises active in SiC crystal growth and device development.
Download or read book Characterization of Silicon Carbide Substrate Defects written by Benjamin D. Poust and published by . This book was released on 2004 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization of Process related Defects in Silicon Carbide by Electron Microscopy written by Per O. Å Persson and published by . This book was released on 2001 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization of Growth Defects in Silicon Carbide Single Crystals by Synchrotron X ray Topography written by Shaoping Wang and published by . This book was released on 1995 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Silicon Carbide written by Peter Friedrichs and published by Wiley-VCH. This book was released on 2009-12-02 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book prestigiously covers our current understanding of SiC as a semiconductor material in electronics. Its physical properties make it more promising for high-powered devices than silicon. The volume is devoted to the material and covers methods of epitaxial and bulk growth. Identification and characterization of defects is discussed in detail. The contributions help the reader to develop a deeper understanding of defects by combining theoretical and experimental approaches. Apart from applications in power electronics, sensors, and NEMS, SiC has recently gained new interest as a substrate material for the manufacture of controlled graphene. SiC and graphene research is oriented towards end markets and has high impact on areas of rapidly growing interest like electric vehicles. The list of contributors reads like a "Who's Who" of the SiC community, strongly benefiting from collaborations between research institutions and enterprises active in SiC crystal growth and device development.
Download or read book Silicon Carbide One dimensional Nanostructures written by Laurence Latu-Romain and published by John Wiley & Sons. This book was released on 2015-02-23 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dedicated to SiC-based 1D nanostructures, this book explains the properties and different growth methods of these nanostructures. It details carburization of silicon nanowires, a growth process for obtaining original Si-SiC core-shell nanowires and SiC nanotubes of high crystalline quality, thanks to the control of the siliconout-diffusion. The potential applications of these particular nano-objects is also discussed, with regards to their eventual integration in biology, energy and electronics.
Download or read book Characterization of Defects and Minority Carrier Lifetime in Silicon Carbide Materials written by A. Rohatgi and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Silicon Carbide Nanowires Thermo mechanical Characterization and Applications for Sustainability written by Jaron Kuppers and published by . This book was released on 2009 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Properties and Applications of Silicon Carbide written by Rosario Gerhardt and published by BoD – Books on Demand. This book was released on 2011-04-04 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, we explore an eclectic mix of articles that highlight some new potential applications of SiC and different ways to achieve specific properties. Some articles describe well-established processing methods, while others highlight phase equilibria or machining methods. A resurgence of interest in the structural arena is evident, while new ways to utilize the interesting electromagnetic properties of SiC continue to increase.
Download or read book Bulk and Nano scale Characterization of Polymer Derived Silicon Carbide and Comparison with Sintered Silicon Carbide written by Arif Rahman and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Defects in Nanocrystals written by Sergio Pizzini and published by CRC Press. This book was released on 2020-05-11 with total page 295 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
