Download or read book Chemical vapour deposition of boron carbon thin films from organoboron precursors written by Maiwulidan (Mewlude) Yimamu (Imam) and published by Linköping University Electronic Press. This book was released on 2016-01-13 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boron-carbon (BxC) thin films enriched in 10B are potential neutron converting layers for 10Bbased solid-state neutron detectors given the good neutron absorption cross-section of 10B atoms in the thin film. Chemical Vapour Deposition (CVD) of such films faces the challenge that the maximum temperature tolerated by the aluminium substrate is 660 °C and low temperature CVD routes for BxC films are thus needed. This thesis presents the use of two different organoboron precursors, triethylboron –B(C2H5)3 (TEB) and trimethylboron – B(CH3)3 (TMB) as single-source precursors for CVD of BxC thin films. The CVD behaviour of TEB in thermal CVD has been studied by both BxC thin film deposition and quantum chemical calculations of the gas phase chemistry at the corresponding CVD conditions. The calculations predict that the gas phase reactions are dominated by ?-hydride eliminations of C2H4 to yield BH3. In addition, a complementary bimolecular reaction path based on H2-assisted C2H6 elimination to BH3 is also present at lower temperatures in the presence of hydrogen molecules. A temperature window of 600 – 1000 °C for deposition of X-ray amorphous BxC films with 2.5 ? x ? 4.5 is identified showing good film density (2.40 – 2.65 g/cm3) which is close to the bulk density of crystalline B4C, 2.52 g/cm3 and high hardness (29 – 39 GPa). The impurity level of H is lowered to < 1 at. % within the temperature window. Plasma chemical vapour deposition has been studied using TMB as single-source precursor in Ar plasma for investigating BxC thin film deposition at lower temperature than allowed by thermal CVD and further understanding of thin film deposition process. The effect of plasma power, total pressure, TMB and Ar gas flow on film composition and morphology are investigated. The highest B/C ratio of 1.9 is obtained at highest plasma power of 2400 W and TMB flow of 7 sccm. The H content in the films seems constant at 15±5 at. %. The B-C bond is dominant in the films with small amount of C-C and B-O bonds, which are likely due to the formation of amorphous carbon and surface oxidation, respectively. The film density is determined as 2.16±0.01 g/cm3 and the internal compressive stresses are measured to be <400 MPa.
Download or read book Chemical Vapour Deposition of sp2 Hybridised Boron Nitride written by Mikhail Chubarov and published by Linköping University Electronic Press. This book was released on 2014-12-04 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this work was to develop a chemical vapour deposition process and understand the growth of sp2 hybridised Boron Nitride (sp2-BN). Thus, the growth on different substrates together with the variation of growth parameters was investigated in details and is presented in the papers included in this thesis. Deposited films of sp2-BN were characterised with the purpose to determine optimal deposition process parameters for the growth of high crystal quality thin films with further investigations of chemical composition, morphology and other properties important for the implementation of this material towards electronic, optoelectronic devices and devices based on graphene/BN heterostructures. For the growth of sp2-BN triethyl boron and ammonia were employed as B and N precursors, respectively. Pure H2 as carrier gas is found to be necessary for the growth of crystalline sp2-BN. Addition of small amount of silane to the gas mixture improves the crystalline quality of the growing sp2-BN film. It was observed that for the growth of crystalline sp2-BN on c-axis oriented ?-Al2O3 a thin and strained AlN buffer layer is needed to support epitaxial growth of sp2-BN, while it was possible to deposit rhombohedral BN (r-BN) on various polytypes of SiC without the need for a buffer layer. The growth temperature suitable for the growth of crystalline sp2-BN is 1500 °C. Nevertheless, the growth of crystalline sp2-BN was also observed on ?-Al2O3 with an AlN buffer layer at a lower temperature of 1200 °C. Growth at this low temperature was found to be hardly controllable due to the low amount of Si that is necessary at this temperature and its accumulation in the reaction cell. When SiC was used as a substrate at the growth temperature of 1200 °C, no crystalline sp2-BN was formed, according to X-ray diffraction. Crystalline structure investigations of the deposited films showed formation of twinned r-BN on both substrates used. Additionally, it was found that the growth on ?-Al2O3 with an AlN buffer layer starts with the formation of hexagonal BN (h-BN) for a thickness of around 4 nm. The formation of h-BN was observed at growth temperatures of 1200 °C and 1500 °C on ?-Al2O3 with AlN buffer layer while there were no traces of h-BN found in the films deposited on SiC substrates in the temperature range between 1200 °C and 1700 °C. As an explanation for such growth behaviour, reproduction of the substrate crystal stacking is suggested. Nucleation and growth mechanism are investigated and presented in the papers included in this thesis.
Download or read book Silicon Carbide written by Moumita Mukherjee and published by BoD – Books on Demand. This book was released on 2011-10-10 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicon Carbide (SiC) and its polytypes, used primarily for grinding and high temperature ceramics, have been a part of human civilization for a long time. The inherent ability of SiC devices to operate with higher efficiency and lower environmental footprint than silicon-based devices at high temperatures and under high voltages pushes SiC on the verge of becoming the material of choice for high power electronics and optoelectronics. What is more important, SiC is emerging to become a template for graphene fabrication, and a material for the next generation of sub-32nm semiconductor devices. It is thus increasingly clear that SiC electronic systems will dominate the new energy and transport technologies of the 21st century. In 21 chapters of the book, special emphasis has been placed on the materials aspects and developments thereof. To that end, about 70% of the book addresses the theory, crystal growth, defects, surface and interface properties, characterization, and processing issues pertaining to SiC. The remaining 30% of the book covers the electronic device aspects of this material. Overall, this book will be valuable as a reference for SiC researchers for a few years to come. This book prestigiously covers our current understanding of SiC as a semiconductor material in electronics. The primary target for the book includes students, researchers, material and chemical engineers, semiconductor manufacturers and professionals who are interested in silicon carbide and its continuing progression.
Download or read book Synthesis and Properties of Boron Nitride written by John J. Pouch and published by Trans Tech Publications. This book was released on 1990 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boron nitride thin films can be deposited on different substrates using techniques such as plasma deposition, ion beam deposition and reactive sputter deposition.
Download or read book Ultrahigh Vacuum Metalorganic Chemical Vapor Deposition and in Situ Characterization of Nanoscale Titanium Dioxide Films written by Polly Wanda Chu and published by . This book was released on 1994 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin titanium dioxide films were produced by metalorganic chemical vapor deposition on sapphire(0001) in an ultrahigh vacuum (UHV) chamber. A method was developed for producing controlled submonolayer depositions from titanium isopropoxide precursor. Film thickness ranged from 0.1 to 2.7 nm. In situ X-ray photoelectron spectroscopy (XPS) was used to determine film stoichiometry with increasing thickness. The effect of isothermal annealing on desorption was evaluated. Photoelectron peak shapes and positions from the initial monolayers were analyzed for evidence of interface reaction. Deposition from titanium isopropoxide is divided into two regimes: depositions below and above the pyrolysis temperature. This temperature was determined to be 300 deg C. Controlled submonolayers of titanium oxide were produced by cycles of dosing with titanium isopropoxide vapor below and annealing above 300 deg C. Precursor adsorption below the pyrolysis temperature was observed to saturate after 15 minutes of dosing. The quantity absorbed was shown to have an upper limit of one monolayer. The stoichiometry of thin films grown by the cycling method were determined to be TiO2. Titanium dioxide film stoichiometry was unaffected by isothermal annealing at 700 deg C. Annealing produced a decrease in film thickness. This was explained as due to desorption. Desorption ceased at approximately 2.5 to 3 monolayers, suggesting bonding of the initial monolayers of film to sapphire is stronger than to itself. Evidence of sapphire reduction at the interface by the depositions was not observed. The XPS O is peak shifted with increased film thickness. The shifts were consistent with oxygen in sapphire and titanium dioxide having different O is photoelectron peak positions. Simulations showed the total shifts for thin films ranging in thickness of 0.1 to 2.7 nm to be -0.99 to -1.23 eV. Thick films were produced for comparison.
Download or read book Chemical Vapor Deposition International Conference written by and published by . This book was released on 1970 with total page 878 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Chemical Vapor Deposition Growth and Characterization of Two Dimensional Hexagonal Boron Nitride written by Roland Yingjie Tay and published by Springer. This book was released on 2018-06-20 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis focuses on the growth of a new type of two-dimensional (2D) material known as hexagonal boron nitride (h-BN) using chemical vapor deposition (CVD). It also presents several significant breakthroughs in the authors’ understanding of the growth mechanism and development of new growth techniques, which are now well known in the field. Of particular importance is the pioneering work showing experimental proof that 2D crystals of h-BN can indeed be hexagonal in shape. This came as a major surprise to many working in the 2D field, as it had been generally assumed that hexagonal-shaped h-BN was impossible due to energy dynamics. Beyond growth, the thesis also reports on synthesis techniques that are geared toward commercial applications. Large-area aligned growth and up to an eightfold reduction in the cost of h-BN production are demonstrated. At present, all other 2D materials generally use h-BN as their dielectric layer and for encapsulation. As such, this thesis lays the cornerstone for using CVD 2D h-BN for this purpose.
Download or read book Deposition of A C B Films from O carborane and Trimethyl Boron Precursors written by Joseph Benjamin Geddes and published by . This book was released on 1996 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Chemical Vapor Deposition written by John Milton Blocher and published by . This book was released on 1970 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Information on the Use of Boron Carbide as a Nuclear Control and Poison Material written by E. W. Hoyt and published by . This book was released on 1961 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Industrial Ceramics written by and published by . This book was released on 1989 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Carbon Nanowalls written by Mineo Hiramatsu and published by Springer Science & Business Media. This book was released on 2010-07-23 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Representing the first text to cover this exciting new area of research, this book will describe synthesis techniques of CNWs, their characterization and various expected applications using CNWs. Carbon-nanowalls (CNWs) can be described as two-dimensional graphite nanostructures with edges comprised of stacks of plane graphene sheets standing almost vertically on the substrate. These sheets form a wall structure with a high aspect ratio. The thickness of CNWs ranges from a few nm to a few tens of nm. The large surface area and sharp edges of CNWs may prove useful for a number of applications such as electrochemical devices, field electron emitters, storage materials for hydrogen gas, catalyst support. In particular, vertically standing CNWs with a high surface-to-volume ratio, serve as an ideal material for catalyst support for fuel cells and in gas storage materials.
Download or read book Boron Rich Solids written by David Emin and published by AIP Conference Proceedings (Nu. This book was released on 1991 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vertically Oriented Graphene written by Junhong Chen and published by Springer. This book was released on 2015-03-23 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the basic concepts, synthesis techniques, and applications of vertically-oriented graphene. The authors detail emerging applications of vertically-oriented graphene such as field emitters, atmospheric nanoscale corona discharges, gas sensors and biosensors, supercapacitors, lithium-ion batteries, fuel cells (catalyst supports) and electrochemical transducers. They offer a perspective on current challenges to enabling commercial applications of vertically-oriented graphene.
Download or read book Core Concepts in Supramolecular Chemistry and Nanochemistry written by Jonathan W. Steed and published by John Wiley & Sons. This book was released on 2007-04-30 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supramolecular chemistry and nanochemistry are two strongly interrelated cutting edge frontiers in research in the chemical sciences. The results of recent work in the area are now an increasing part of modern degree courses and hugely important to researchers. Core Concepts in Supramolecular Chemistry and Nanochemistry clearly outlines the fundamentals that underlie supramolecular chemistry and nanochemistry and takes an umbrella view of the whole area. This concise textbook traces the fascinating modern practice of the chemistry of the non-covalent bond from its fundamental origins through to it expression in the emergence of nanochemistry. Fusing synthetic materials and supramolecular chemistry with crystal engineering and the emerging principles of nanotechnology, the book is an ideal introduction to current chemical thought for researchers and a superb resource for students entering these exciting areas for the first time. The book builds from first principles rather than adopting a review style and includes key references to guide the reader through influential work. supplementary website featuring powerpoint slides of the figures in the book further references in each chapter builds from first principles rather than adopting a review style includes chapter on nanochemistry clear diagrams to highlight basic principles
Download or read book Boron Based Compounds written by Evamarie Hey-Hawkins and published by John Wiley & Sons. This book was released on 2018-07-23 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt: Noted experts review the current status of boron-containing drugs and materials for molecular medical diagnostics Boron-Based Compounds offers a summary of the present status and promotes the further development of new boron-containing drugs and advanced materials, mostly boron clusters, for molecular medical diagnostics. The knowledge accumulated during the past decades on the chemistry and biology of bioorganic and organometallic boron compounds laid the foundation for the emergence of a new area of study and application of boron compounds as lipophilic pharmacophores and modulators of biologically active molecules.This important text brings together in one comprehensive volume contributions from renowned experts in the field of medicinal chemistry of boron compounds. The authors cover a range of the most relevant topics including boron compounds as modulators of the bioactivity of biomolecules, boron clusters as pharmacophores or for drug delivery, boron compounds for boron neutron capture therapy (BNCT) and for diagnostics, as well as in silico molecular modeling of boron- and carborane-containing compounds in drug design. Authoritative and accessible, Boron-Based Compounds: Contains contributions from a panel of internationally renowned experts in the field Offers a concise summary of the current status of boron-containing drugs and materials used for molecular diagnostics Highlights the range and capacity of boron-based compounds in medical applications Includes information on boron neutron capture therapy and diagnostics Designed for academic and industrial scientists, this important resource offers the cutting-edge information needed to understand the current state of boron-containing drugs and materials for molecular medical diagnostics.
Download or read book Conservation of Wood Artifacts written by A. Unger and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: The impetus for this book was the desire to systematically organize the extant literature on the conservation of cultural property made of wood, from its beginnings before the Christian Era to the year 2000. Various published reviews and monographs, including Holzkonservierung (Wood Conserva tion) published by the senior author in 1988, have appeared over the years, especially in English and in German. They have provided exemplary treat merit of individual areas or aspects of wood conservation, but a comprehen sive, up-to-date exposition of historic and current developments has been lacking. The diverse professional fields of the authors, as well as their insights into methods of conservation and restoration of wood artifacts in Europe, North America, and Asia provided a solid basis for the success of this under taking. One of the goals during the examination of the literature was that not only well-known conservators and scientists from countries that are leaders in wood conservation should be represented, but that less well-known, often not as readily accessible contributions should also be included. Only in this manner was it possible to draw a comprehensive picture of the national and international state of wood conservation. The Art and Archaeology Technical Abstracts (AATA) of the Getty Institute were very helpful in our efforts to evaluate as many publications as possible.
