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Direct Observations Of Atomic Structures Of Defects In Gan By High Resolution Z Contrast Stem
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Book Synopsis Direct Observations of Atomic Structures of Defects in GaN by High-resolution Z-contrast STEM. by :
Download or read book Direct Observations of Atomic Structures of Defects in GaN by High-resolution Z-contrast STEM. written by and published by . This book was released on 1997 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: GaN/(0001) Sapphire grown by low pressure MOVPE is studied by high resolution Z-contrast imaging using STEM. First direct observation of the threading dislocation with edge character shows the atomic core structure, which appears to have a similar configuration to the {l_brace}10-10{r_brace} surface. The surfaces of the nanopipe walls are on {l_brace}10-10{r_brace} with the terminating layer between the atoms with one bond per pair. In addition, the high resolution Z contrast image of the prismatic stacking fault confirms the results by conventional HRTEM.
Book Synopsis Direct Observations of Defect Structures in Optoelectronic Materials by Z-contrast STEM. by :
Download or read book Direct Observations of Defect Structures in Optoelectronic Materials by Z-contrast STEM. written by and published by . This book was released on 1998 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optoelectronic semiconductor materials have wide and important technological applications. For example, wide gap nitride semiconductors have attracted significant attention recently due to their promising performance as short-wavelength light emitting diodes (LEDs) and blue lasers, while HgCdTe II-VI semiconductors are the most promising candidates for applications as infrared detectors, or large array x-ray or gamma-ray detectors. In this paper, two examples are given to show that high-resolution Z-contrast imaging is an effective technique to determine the atomic structures of defects in these complex semiconductor materials. One interesting issue concerning GaN is that the material is relatively insensitive to the presence of a density of dislocations which is six orders of magnitude higher than that for III-V arsenide and phosphide based LEDs. To develop a fundamental understanding of the properties of the dislocations in GaN, the core structures are determined here by atomic-resolution Z-contrast imaging in a scanning transmission electron microscope (STEM) with a resolution of 0.13 nm. As the Z-contrast image is a convolution between the probe intensity profile and the specimen object function, it is possible to obtain detailed information on the atomic column positions through maximum entropy analysis. For a sphalerite semiconductor, polarity is an important issue, as the asymmetry of the structure gives rise to different physical and chemical properties. Here the authors show that high resolution Z-contrast imaging could be used as an effective method to determine the polarity of II-VI semiconductors without referring to reference samples or image simulations.
Book Synopsis Direct Observation of Threading Dislocations in GaN by High-resolution Z-contrast Imaging by :
Download or read book Direct Observation of Threading Dislocations in GaN by High-resolution Z-contrast Imaging written by and published by . This book was released on 1998 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wide gap nitride semiconductors have attracted significant attention recently due to their promising performance as short-wavelength light emitting diodes (LEDs) and blue lasers. One interesting issue concerning GaN is that the material is relatively insensitive to the presence of a density of dislocations which is six orders of magnitude higher than that for III-V arsenide and phosphide based LEDs. Although it is well known that these dislocations originate at the film-substrate interface during film growth, thread through the whole epilayer with line direction along 0001 and are perfect dislocations with Burgers vectors of a, c, or c+a, the reason why they have such a small effect on the properties of GaN is unclear. To develop a fundamental understanding of the properties of these dislocations, the core structures are studied here by high resolution Z-contrast imaging in a 300kV VG HB603 scanning transmission electron microscope (STEM) with a resolution of 0.13 nm. As the Z-contrast image is a convolution between the probe intensity profile and the specimen object function, it is possible to obtain more detailed information on the specimen object function, i.e. the structure, through maximum entropy analysis (the maximum entropy technique produces the ''most likely'' object function which is consistent with the image).
Book Synopsis Atomic Structure of Defects in GaN by : Z. Liliental-Weber
Download or read book Atomic Structure of Defects in GaN written by Z. Liliental-Weber and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Electron microscope phase images, produced by direct reconstruction of the scattered electron wave from a focal series of high-resolution images, were used to determine the nature of defects formed in GaN:Mg crystals. We studied bulk crystals grown from dilute solutions of atomic nitrogen in liquid gallium at high pressure and thin films grown by the MOCVD method. All the crystals were grown with Ga-polarity. In both types of samples the majority of defects were three dimensional Mg-rich hexagonal pyramids with bases on the (0001) plane and six walls on {l_brace}11{und 2}3{r_brace} planes seen in cross-section as triangulars. Some other defects appear in cross-section as trapezoidal (rectangular) defects as a result of presence of truncated pyramids. Both type of defects have hollow centers. They are decorated by Mg on all six side walls and a base. The GaN which grows inside on the defect walls shows polarity inversion. It is shown that change of polarity starts from the defect tip and propagates to the base, and that the stacking sequence changes from ab in the matrix to bc inside the defect. Exchange of the Ga sublattice with the N sublattice within the defect leads to 0.6 {+-} 0.2{angstrom} displacement between Ga sublattices outside and inside the defects. It is proposed that lateral overgrowth of the cavities formed within the defect takes place to restore matrix polarity on the defect base.
Download or read book Electron Microscopy written by and published by . This book was released on 1998 with total page 854 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Defects in P-GaN and Their Atomic Structure by : Z. Liliental-Weber
Download or read book Defects in P-GaN and Their Atomic Structure written by Z. Liliental-Weber and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper defects formed in p-doped GaN:Mg grown with Ga polarity will be discussed. The atomic structure of these characteristic defects (Mg-rich hexagonal pyramids and truncated pyramids) in bulk and thin GaN:Mg films grown with Ga polarity was determined at atomic resolution by direct reconstruction of the scattered electron wave in a transmission electron microscope. Small cavities were present inside the defects. The inside walls of the cavities were covered by GaN which grew with reverse polarity compared to the matrix. It was proposed that lateral overgrowth of the cavities restores matrix polarity on the defect base. Exchange of Ga and N sublattices within the defect compared to the matrix lead to a 0.6 {+-} 0.2 {angstrom} displacement between the Ga sublattices of these two areas. A [1{und 1}00]/3 shift with change from AB stacking in the matrix to BC within the entire pyramid is observed.
Book Synopsis Impact of Electron and Scanning Probe Microscopy on Materials Research by : David G. Rickerby
Download or read book Impact of Electron and Scanning Probe Microscopy on Materials Research written by David G. Rickerby and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 503 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Advanced Study Institute provided an opportunity for researchers in universities, industry and National and International Laboratories, from the disciplines ofmaterials science, physics, chemistry and engineering to meet together in an assessment of the impact of electron and scanning probe microscopy on advanced material research. Since these researchers have traditionally relied upon different approaches, due to their different scientific background, to advanced materials problem solving, presentations and discussion within the Institute sessions were initially devoted to developing a set ofmutually understood basic concepts, inherently related to different techniques ofcharacterization by microscopy and spectroscopy. Particular importance was placed on Electron Energy Loss Spectroscopy (EELS), Scanning Probe Microscopy (SPM), High Resolution Transmission and Scanning Electron Microscopy (HRTEM, HRSTEM) and Environmental Scanning Electron Microscopy (ESEM). It was recognized that the electronic structure derived directly from EELS analysis as well as from atomic positions in HRTEM or High Angle Annular Dark Field STEM can be used to understand the macroscopic behaviour of materials. The emphasis, however, was upon the analysis of the electronic band structure of grain boundaries, fundamental for the understanding of macroscopic quantities such as strength, cohesion, plasticity, etc.
Book Synopsis Denshi Kembikyō Gakkai Shi; Kikan by :
Download or read book Denshi Kembikyō Gakkai Shi; Kikan written by and published by . This book was released on 2001 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Atomic Structure of Pyramidal Defects in GaN by :
Download or read book Atomic Structure of Pyramidal Defects in GaN written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The atomic structure of the characteristic defects (Mg-rich hexagonal pyramids) in p-doped bulk and MOCVD GaN:Mg thin films grown with Ga polarity was determined at atomic resolution by direct reconstruction of the scattered electron wave in a transmission electron microscope. Small cavities were present inside the defects, confirmed also with positron annihilation. The inside walls of the cavities were covered by GaN of reverse polarity compared to the matrix. Defects in bulk GaN:Mg were almost one order of magnitude larger than in thin films. An exchange of Ga and N sublattices within the defect compared to the matrix lead to a 0.6 ± 0.2 Å displacement between the Ga sublattices of these two areas. A [1100]/3 shift with change from AB stacking in the matrix to BC within the entire pyramid was observed. Annealing of the MOCVD layers lead to slight increase of the defect size and an increase of the photoluminescence intensity. Positron annihilation confirms presence of vacancies of different sizes triggered by the Mg doping in as-grown samples and decrease of their concentration upon annealing at 900 and 1000 C.
Book Synopsis Nitride Semiconductor Technology by : Fabrizio Roccaforte
Download or read book Nitride Semiconductor Technology written by Fabrizio Roccaforte and published by John Wiley & Sons. This book was released on 2020-07-30 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book "Nitride Semiconductor Technology" provides an overview of nitride semiconductors and their uses in optoelectronics and power electronics devices. It explains the physical properties of those materials as well as their growth methods. Their applications in high electron mobility transistors, vertical power devices, LEDs, laser diodes, and vertical-cavity surface-emitting lasers are discussed in detail. The book further examines reliability issues in these materials and puts forward perspectives of integrating them with 2D materials for novel high-frequency and high-power devices. In summary, it covers nitride semiconductor technology from materials to devices and provides the basis for further research.
Book Synopsis Transmission Electron Microscopy by : C. Barry Carter
Download or read book Transmission Electron Microscopy written by C. Barry Carter and published by Springer. This book was released on 2016-08-24 with total page 543 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text is a companion volume to Transmission Electron Microscopy: A Textbook for Materials Science by Williams and Carter. The aim is to extend the discussion of certain topics that are either rapidly changing at this time or that would benefit from more detailed discussion than space allowed in the primary text. World-renowned researchers have contributed chapters in their area of expertise, and the editors have carefully prepared these chapters to provide a uniform tone and treatment for this exciting material. The book features an unparalleled collection of color figures showcasing the quality and variety of chemical data that can be obtained from today’s instruments, as well as key pitfalls to avoid. As with the previous TEM text, each chapter contains two sets of questions, one for self assessment and a second more suitable for homework assignments. Throughout the book, the style follows that of Williams & Carter even when the subject matter becomes challenging—the aim is always to make the topic understandable by first-year graduate students and others who are working in the field of Materials Science Topics covered include sources, in-situ experiments, electron diffraction, Digital Micrograph, waves and holography, focal-series reconstruction and direct methods, STEM and tomography, energy-filtered TEM (EFTEM) imaging, and spectrum imaging. The range and depth of material makes this companion volume essential reading for the budding microscopist and a key reference for practicing researchers using these and related techniques.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :F. Nieto Publisher :The Mineralogical Society of Great Britain and Ireland ISBN 13 :0903056348 Total Pages :456 pages Book Rating :4.9/5 (3 download)
Book Synopsis Minerals at the Nanoscale by : F. Nieto
Download or read book Minerals at the Nanoscale written by F. Nieto and published by The Mineralogical Society of Great Britain and Ireland. This book was released on 2013-05-24 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: The editors have gathered in this book, reviews of past and current studies of mineral groups that have played important roles in geology, environmental science and health science. The various chapters cover the application of TEM and related techniques to: mineral groups in which TEM investigations have been extensive and crucial to the understanding of their mineralogy, namely pyriboles, serpentines, clays, micas and other metamorphic phyllosilicates, oxides and oxyhydroxides, sulfides and carbonates. Some research fields for which TEM is particularly suitable and which have produced significant advances, in particular, are inclusions and traces, extraterrestrial material, deformation processes, non-stoichiometry and superstructures, and biominerals. Nowadays, we are witnessing the push for the improvement of detectors for imaging (direct detection of electrons) and X-rays (silicon drift detectors and annular high solid-angle of collection detectors), the development of new support materials (e.g. graphene) and liquid cells for TEMs. Most of these new technologies have not yet been applied to mineralogical problems but we hope they will be in the near future.
Book Synopsis Springer Handbook of Microscopy by : Peter W. Hawkes
Download or read book Springer Handbook of Microscopy written by Peter W. Hawkes and published by Springer Nature. This book was released on 2019-11-02 with total page 1561 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book features reviews by leading experts on the methods and applications of modern forms of microscopy. The recent awards of Nobel Prizes awarded for super-resolution optical microscopy and cryo-electron microscopy have demonstrated the rich scientific opportunities for research in novel microscopies. Earlier Nobel Prizes for electron microscopy (the instrument itself and applications to biology), scanning probe microscopy and holography are a reminder of the central role of microscopy in modern science, from the study of nanostructures in materials science, physics and chemistry to structural biology. Separate chapters are devoted to confocal, fluorescent and related novel optical microscopies, coherent diffractive imaging, scanning probe microscopy, transmission electron microscopy in all its modes from aberration corrected and analytical to in-situ and time-resolved, low energy electron microscopy, photoelectron microscopy, cryo-electron microscopy in biology, and also ion microscopy. In addition to serving as an essential reference for researchers and teachers in the fields such as materials science, condensed matter physics, solid-state chemistry, structural biology and the molecular sciences generally, the Springer Handbook of Microscopy is a unified, coherent and pedagogically attractive text for advanced students who need an authoritative yet accessible guide to the science and practice of microscopy.
Book Synopsis Defects in Self-Catalysed III-V Nanowires by : James A. Gott
Download or read book Defects in Self-Catalysed III-V Nanowires written by James A. Gott and published by Springer Nature. This book was released on 2022-01-28 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents an in-depth exploration of imperfections that can be found in self-catalysed III-V semiconductor nanowires. By utilising advanced electron microscopy techniques, the interface sharpness and defects at the atomic and macroscopic scale are analysed. It is found that a surprising variety and quantity of defect structures can exist in nanowire systems, and that they can in fact host some never-before-seen defect configurations. To probe how these defects are formed, conditions during nanowire growth can be emulated inside the microscope using the latest generation of in-situ heating holder. This allowed the examination of defect formation, dynamics, and removal, revealing that many of the defects can in fact be eliminated. This information is critical for attaining perfect nanowire growth. The author presents annealing strategies to improve crystal quality, and therefore device performance.
Book Synopsis Scanning Transmission Electron Microscopy by : Stephen J. Pennycook
Download or read book Scanning Transmission Electron Microscopy written by Stephen J. Pennycook and published by Springer Science & Business Media. This book was released on 2011-03-24 with total page 764 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scanning transmission electron microscopy has become a mainstream technique for imaging and analysis at atomic resolution and sensitivity, and the authors of this book are widely credited with bringing the field to its present popularity. Scanning Transmission Electron Microscopy(STEM): Imaging and Analysis will provide a comprehensive explanation of the theory and practice of STEM from introductory to advanced levels, covering the instrument, image formation and scattering theory, and definition and measurement of resolution for both imaging and analysis. The authors will present examples of the use of combined imaging and spectroscopy for solving materials problems in a variety of fields, including condensed matter physics, materials science, catalysis, biology, and nanoscience. Therefore this will be a comprehensive reference for those working in applied fields wishing to use the technique, for graduate students learning microscopy for the first time, and for specialists in other fields of microscopy.
Download or read book Nanoinformatics written by Isao Tanaka and published by Springer. This book was released on 2018-01-15 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book brings out the state of the art on how informatics-based tools are used and expected to be used in nanomaterials research. There has been great progress in the area in which “big-data” generated by experiments or computations are fully utilized to accelerate discovery of new materials, key factors, and design rules. Data-intensive approaches play indispensable roles in advanced materials characterization. "Materials informatics" is the central paradigm in the new trend. "Nanoinformatics" is its essential subset, which focuses on nanostructures of materials such as surfaces, interfaces, dopants, and point defects, playing a critical role in determining materials properties. There have been significant advances in experimental and computational techniques to characterize individual atoms in nanostructures and to gain quantitative information. The collaboration of researchers in materials science and information science is growing actively and is creating a new trend in materials science and engineering.
