Download or read book SEEDED PHYSICAL VAPOR TRANSPORT OF CADMIUM ZINC TELLURIDE CRYSTALS GROWTH AND CHARACTERIZATION NASA TM 97 207738 JUN 1 1998 written by United States. National Aeronautics and Space Administration and published by . This book was released on 1999* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book GROWTH OF CADMIUM ZINC TELLURIDE CRYSTALS BY CONTROLLED SEEDING CONTRACTLESS PHYSICAL VAPOR TRANSPORT NASA CR 204728 SEP 18 1997 written by United States. National Aeronautics and Space Administration and published by . This book was released on 1998* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book CHARACTERIZATION OF CADMIUM ZINC TELLURIDE CRYSTALS GROWN BY CONTACTLESS PVT USING SYNCHROTRON WHITE BEAM NASA TM 97 207869 SEP 15 1998 written by United States. National Aeronautics and Space Administration and published by . This book was released on 1999* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vapor Crystal Growth Technology Development written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-11-02 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Growth of bulk crystals by physical vapor transport was developed and applied to cadmium telluride. The technology makes use of effusive ampoules, in which part of the vapor contents escapes to a vacuum shroud through defined leaks during the growth process. This approach has the advantage over traditional sealed ampoule techniques that impurity vapors and excess vapor constituents are continuously removed from the vicinity of the growing crystal. Thus, growth rates are obtained routinely at magnitudes that are rather difficult to achieve in closed ampoules. Other advantages of this effusive ampoule physical vapor transport (EAPVT) technique include the predetermination of transport rates based on simple fluid dynamics and engineering considerations, and the growth of the crystal from close to congruent vapors, which largely alleviates the compositional nonuniformities resulting from buoyancy driven convective transport. After concisely reviewing earlier work on improving transport rates, nucleation control, and minimization of crystal wall interactions in vapor crystal growth, a detail account is given of the largely computer controlled EAPVT experimentation. Rosenberger, Franz and Banish, Michael and Duval, Walter M. B. Glenn Research Center...
Download or read book CHARACTERIZATION OF CADMIUM ZINC TELLURIDE CRYSTALS GROWN BY CONTACTLESS PVT USING SYNCHROTRON WHITE BEAM NASA written by and published by . This book was released on 1999* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Developments in Cadmium Zinc Telluride Crystal Growth Sample Preparation and Characterisation sic Techniques written by Amlan Datta and published by . This book was released on 2010 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Simulation and Growth of Cadmium Zinc Telluride from Small Seeds by the Travelling Heater Method written by Jordan Douglas Roszmann and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The semiconducting compounds CdTe and CdZnTe have important applications in high-energy radiation detectors and as substrates for infrared devices. The materials offer large band gaps, high resistivity, and excellent charge transport properties; however all of these properties rely on very precise control of the material composition. Growing bulk crystals by the travelling heater method (THM) offers excellent compositional control and fewer defects compared to gradient freezing, but it is also much slower and more expensive. A particular challenge is the current need to grow new crystals onto existing seeds of similar size and quality. Simulations and experiments are used in this work to investigate the feasibility of growing these materials by THM without the use of large seed crystals. A new fixed-grid, multiphase finite element model was developed based on the level set method and used to calculate the mass transport regime and interface shapes inside the growth ampoule. The diffusivity of CdTe in liquid tellurium was measured through dissolution experiments, which also served to validate the model. Simulations of tapered THM growth find conditions similar to untapered growth with interface shapes that are sensitive to strong thermosolutal convection. Favourable growth conditions are achievable only if convection can be controlled. In preliminary experiments, tapered GaSb crystals were successfully grown by THM and large CdTe grains were produced by gradient freezing. Beginning with this seed material, 25 mm diameter CdTe and CdZnTe crystals were grown on 10 mm diameter seeds, and 65 mm diameter CdTe on 25 mm seeds. Unseeded THM growth was also investigated, as well as ampoule rotation and a range of thermal conditions and ampoule surface coatings. Outward growth beyond one or two centimeters was achieved only at small diameters and included secondary grains and twin defects; however, limited outward growth of larger seeds and agreement between experimental and numerical results suggest that tapered growth may be achievable in the future. This would require active temperature control at the base of the crystal and reduction of convection through thermal design or by rotation of the ampoule or applied magnetic fields.
Download or read book Crystal Growth of Znse and Related Ternary Compound Semiconductors by Physical Vapor Transport written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: The materials to be investigated are ZnSe and related ternary semiconducting alloys (e.g., ZnS(x)Se(1-x), ZnTe(x)Se(1-x), and Zn(1-x)Cd(x)Se). These materials are useful for opto-electronic applications such as high efficient light emitting diodes and low power threshold and high temperature lasers in the blue-green region of the visible spectrum. The recent demonstration of its optical bistable properties also makes ZnSe a possible candidate material for digital optical computers. The investigation consists of an extensive ground-based study followed by flight experimentation, and involves both experimental and theoretical work. The objectives of the ground-based work are to establish the characteristics of the crystals grown on Earth as a basis for subsequent comparative evaluations of the crystals grown in a low gravity environment and to obtain the experimental data and perform the analyses required to define the optimum parameters for the flight experiments. During the six months of the Preliminary Definition Phase, the research efforts were concentrated on the binary compound ZnSe - the purification of starting materials of Se by zone refining, the synthesis of ZnSe starting materials, the heat treatments of the starting materials, the vapor transport rate measurements, the vapor partial pressure measurements of ZnSe, the crystal growth of ZnSe by physical vapor transport, and various characterization on the grown ZnSe crystals. Su, Ching-Hua Unspecified Center NAS8-39718...
Download or read book Characterization of Cadmium zinc Telluride Crystals Grown by contactless PVT Using Synchrotron White Beam Topography written by Witold Palosz and published by . This book was released on 1997 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Global Modeling of Bulk Crystal Growth of Cadmium Zinc Telluride in Industrial VB VGF Systems written by Arun Pandy and published by . This book was released on 2004 with total page 762 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Large Volume Single Crystal Growth of Cadmium Zinc Telluride with Minimal Secondary Phases for Room Temperature Radiation Detector Application written by Santosh Kumar Swain and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Two major aspects of Cadmium Zinc Telluride (CdZnTe) crystal growth for room temperature radiation detection application namely tellurium rich second phase defects and single crystal yield have been addressed. Various approaches were considered towards the minimization of these defects both during growth and post growth thermal treatment in cadmium environment. Since the issue of retrograde solubility in CdZnTe pseudo binary alloy system causes tellurium precipitation, different cooling mechanisms were also devised to achieve minimal secondary phases. Some important and encouraging results were obtained relative to the size and distribution of secondary phases upon growing the crystal with different growth rate and different cooling rate of the crystal after growth. Thermomigration of tellurium were also observed while post processing samples in a temperature gradient, in (Cd, Zn) atmosphere. Results indicated orders of magnitude reduction on secondary phases at the expense of sample resistivity.
Download or read book Study on Thermal Annealing of Cadmium Zinc Telluride CZT Crystals written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Cadmium Zinc Telluride (CZT) has attracted increasing interest with its promising potential as a room-temperature nuclear-radiation-detector material. However, different defects in CZT crystals, especially Te inclusions and dislocations, can degrade the performance of CZT detectors. Post-growth annealing is a good approach potentially to eliminate the deleterious influence of these defects. At Brookhaven National Laboratory (BNL), we built up different facilities for investigating post-growth annealing of CZT. Here, we report our latest experimental results. Cd-vapor annealing reduces the density of Te inclusions, while large temperature gradient promotes the migration of small-size Te inclusions. Simultaneously, the annealing lowers the density of dislocations. However, only-Cd-vapor annealing decreases the resistivity, possibly reflecting the introduction of extra Cd in the lattice. Subsequent Te-vapor annealing is needed to ensure the recovery of the resistivity after removing the Te inclusions.
Download or read book Deep Level Characterization of Seeded Physical Vapor Transport Zinc Selenide written by Brian Gerard Markey and published by . This book was released on 1993 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optimization of Cadmium Zinc Telluride Crystal Growth for Room Temperature Radiation Detectors written by Kelly Allan Jones 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 Crystal Growth of Znse and Related Ternary Compound Semiconductors by Physical Vapor Transport written by Nasa Technical Reports Server (Ntrs) and published by BiblioGov. This book was released on 2013-07-01 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: The NASA Technical Reports Server (NTRS) houses half a million publications that are a valuable means of information to researchers, teachers, students, and the general public. These documents are all aerospace related with much scientific and technical information created or funded by NASA. Some types of documents include conference papers, research reports, meeting papers, journal articles and more. This is one of those documents.
Download or read book Development of Traveling Heater Method to Grow Cadmium Telluride CdTe Cadmium Zinc Telluride CZT Crystals written by Manchanahalli S. Rohan Rao and published by . This book was released on 2011 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optical and Electrical Characterization of Seeded Physical Vapor Transport Zinc Selenide written by Hector Luis Cotal and published by . This book was released on 1993 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
