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Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Structure of silicon carbide wafers have been evaluated by x-ray topography, high resolution x-ray diffraction, etching, Atomic Force Microscopy, and related techniques. The low angle grain boundaries were imaged by White Beam Synchrotron X-Ray Topography and mis-orientations quantitatively mapped out by x-ray diffraction. The dominant component of mis-orientation was basal plane tilt. The formation mechanism is most likely due to buckling of the rigidly mounted SiC seed during initial stages of growth. The morphology of hexagonal voids was studied by optical microscopy and AFM. Voids originate at the seed crystal/crucible lid interface and move through the boule during growth. Interaction of void and grown in dislocations leads to formation of dislocation arrays and open core screw dislocations underneath the void. It appears to be the dominant formation mechanism of micropipes.
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Structure of silicon carbide wafers have been evaluated by x-ray topography, high resolution x-ray diffraction, etching, Atomic Force Microscopy, and related techniques. The low angle grain boundaries were imaged by White Beam Synchrotron X-Ray Topography and mis-orientations quantitatively mapped out by x-ray diffraction. The dominant component of mis-orientation was basal plane tilt. The formation mechanism is most likely due to buckling of the rigidly mounted SiC seed during initial stages of growth. The morphology of hexagonal voids was studied by optical microscopy and AFM. Voids originate at the seed crystal/crucible lid interface and move through the boule during growth. Interaction of void and grown in dislocations leads to formation of dislocation arrays and open core screw dislocations underneath the void. It appears to be the dominant formation mechanism of micropipes.
Author: Joshua Taylor Jarrell Publisher: ISBN: Category : Nuclear engineering Languages : en Pages : 195
Book Description
There exists a need for monitoring the actinide concentrations in elevated temperature molten salt environments. Reprocessing of used nuclear fuel through pyroprocessing is being investigated as a viable method to manage the growing stockpile of used nuclear fuel. Idaho National Laboratory has demonstrated the ability to reprocess both breeder and blanket fuel from the Experimental Breeder Reactor II using an electrorefining system. This system uses a molten eutectic salt mixture of lithium chloride and potassium chloride. This electrorefining system can produce high purity uranium ingots and mixed uranium-plutonium ingots. The fundamental electrochemistry used for this process precludes the separation of high purity plutonium when operated within the suggested process limits. However, special nuclear material may be diverted by operating outside of the normal process. Complete draw down of the uranium dissolved into the molten salt would allow for the subsequent removal of high purity plutonium. Monitoring of the operational history of the electrorefiner is therefore essential to address these non-proliferation and safeguard concerns. There is thus a need to monitor the concentrations of individual elements and isotopes present in the electrorefiner salt. Currently, such assays require time on the order of weeks to provide an accurate description of isotopic concentrations within the salt. Thus, a near real-time measurement system for the actinide isotopic concentrations within the salt is needed. All actinide isotopes of interest to non-proliferation and safeguards interests emit characteristic alpha particles. Semiconductor radiation detectors have been shown to provide a compact, high energy resolution solution to spectroscopic measurement needs. Silicon carbide, a wide band-gap semiconductor, provides elevated temperature operation capability and corrosion resistance in the molten salt environment that is superior to silicon. As a result, for this work, alpha radiation detectors comprised of 4H-SiC with Schottky barrier contacts have been fabricated and shown to operate above 500oC. Detector contact compositions of nickel-platinum was explored as possible Schottky contact structures. The electrical and diode characteristics of the detectors were measured. Alpha spectra from multiple source isotopes and source geometries were obtained in vacuum with the detector heated from 20oC to 500oC. The resulting detector behavior including alpha spectrum centroid position and detector energy resolution were measured. To avoid energy attenuation in the molten salt, a repeatable method for depositing actinides to the surface of the detector was devised that allows for repeated spectroscopic measurements by a single detector. The resilience of detector performance to submersion in a molten salt was investigated as well as energy resolution during elevated temperature operation. Detectors were characterized prior to being submerged in a 500oC molten LiCl-KCl eutectic salt for increasing time intervals. After submersion, the detectors were again characterized to identify any degradation. Detector packaging capable of withstanding the corrosive 500oC molten salt environment was developed which allows for electrical connections between the detector and spectrometry equipment. The packaging was designed to allow for actinide deposition on the active area of the detector, allowing for accurate calculations of the actinide mass deposited by a known current. Additionally, nuclear forensic applications of 4H-SiC alpha detectors in conjunction with electrodeposited source fabrication were explored. A method was determined to calculate the 235U enrichment in the product stream of an enrichment facility through measurement of the 234U and 235U enrichments in an electrodeposited source fabricated from depleted uranium.
Author: Stephen J. Pearton Publisher: CRC Press ISBN: 1000448428 Category : Science Languages : en Pages : 556
Book Description
Presents views on current developments in heat and mass transfer research related to the modern development of heat exchangers. Devotes special attention to the different modes of heat and mass transfer mechanisms in relation to the new development of heat exchangers design. Dedicates particular attention to the future needs and demands for further development in heat and mass transfer. GaN and related materials are attracting tremendous interest for their applications to high-density optical data storage, blue/green diode lasers and LEDs, high-temperature electronics for high-power microwave applications, electronics for aerospace and automobiles, and stable passivation films for semiconductors. In addition, there is great scientific interest in the nitrides, because they appear to form the first semiconductor system in which extended defects do not severely affect the optical properties of devices. This series provides a forum for the latest research in this rapidly-changing field, offering readers a basic understanding of new developments in recent research. Series volumes feature a balance between original theoretical and experimental research in basic physics, device physics, novel materials and quantum structures, processing, and systems.
Author: Matteo Meneghini Publisher: Springer ISBN: 3319431994 Category : Technology & Engineering Languages : en Pages : 383
Book Description
This book presents the first comprehensive overview of the properties and fabrication methods of GaN-based power transistors, with contributions from the most active research groups in the field. It describes how gallium nitride has emerged as an excellent material for the fabrication of power transistors; thanks to the high energy gap, high breakdown field, and saturation velocity of GaN, these devices can reach breakdown voltages beyond the kV range, and very high switching frequencies, thus being suitable for application in power conversion systems. Based on GaN, switching-mode power converters with efficiency in excess of 99 % have been already demonstrated, thus clearing the way for massive adoption of GaN transistors in the power conversion market. This is expected to have important advantages at both the environmental and economic level, since power conversion losses account for 10 % of global electricity consumption. The first part of the book describes the properties and advantages of gallium nitride compared to conventional semiconductor materials. The second part of the book describes the techniques used for device fabrication, and the methods for GaN-on-Silicon mass production. Specific attention is paid to the three most advanced device structures: lateral transistors, vertical power devices, and nanowire-based HEMTs. Other relevant topics covered by the book are the strategies for normally-off operation, and the problems related to device reliability. The last chapter reviews the switching characteristics of GaN HEMTs based on a systems level approach. This book is a unique reference for people working in the materials, device and power electronics fields; it provides interdisciplinary information on material growth, device fabrication, reliability issues and circuit-level switching investigation.
Author: Didier Decoster Publisher: John Wiley & Sons ISBN: 1118622928 Category : Technology & Engineering Languages : en Pages : 246
Book Description
Optoelectronic sensors combine optical and electronic systems for numerous applications including pressure sensors, security systems, atmospheric particle measurement, close tolerance measurement, quality control, and more. This title provides an examination of the latest research in photonics and electronics in the areas of sensors.
Author: Silvano Donati Publisher: John Wiley & Sons ISBN: 1119769949 Category : Science Languages : en Pages : 464
Book Description
Explore this comprehensive introduction to the foundations of photodetection from one of the leading voices in the field The newly revised Photodetectors: Devices, Circuits and Applications delivers a thoroughly updated exploration of the fundamentals of photodetection and the novel technologies and concepts that have arisen since the release of the first edition twenty years ago. The book offers discussions of established and emerging photodetection technologies, including photomultipliers, the SPAD, the SiPM, the SNSPD, the UTC, the WGPD/TWPD, the QWIP, and the LT-GaAs. New examinations of correlation measurements on ultrafast pulses and single-photon detectors for quantum communications and LiDARs have also been added. Each chapter includes selected problems for students to work through to aid in learning and retention. A booklet of solutions is also provided. The book is especially ideal for students and faculties of Engineering, with an emphasis on first principles, design, and the engineering of photodetectors. Issues in the book are grouped through the development of concepts, as opposed to collections of technical details. Perfect for undergraduate students interested in the science or design of modern optoelectronics, Photodetectors: Devices, Circuits and Applications also belongs on the bookshelves of professors teaching PhD seminars in advanced courses on photodetection and noise, as well as engineers and physicists seeking a guide to an optimum photodetection solution.
Author: Antoni Rogalski Publisher: SPIE-International Society for Optical Engineering ISBN: 9781510611399 Category : Antimonides Languages : en Pages :
Book Description
"Among the many materials investigated in the infrared (IR) field, narrow-gap semiconductors are the most important in IR photon detector family. Although the first widely used narrow-gap materials were lead salts (during the 1950s, IR detectors were built using single-element-cooled PbS and PbSe photoconductive detectors, primary for anti-missile seekers), this semiconductor family was not well distinguished. This situation seems to have resulted from two reasons: the preparation process of lead salt photoconductive polycrystalline detectors was not well understood and could only be reproduced with well-tried recipes; and the theory of narrow-gap semiconductor bandgap structure was not well known for correct interpretation of the measured transport and photoelectrical properties of these materials"--
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Author: Joshua Taylor Jarrell
Author: Stephen J. Pearton
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Author: Matteo Meneghini
Author: Didier Decoster
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Author: Silvano Donati
Author: Antoni Rogalski