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Book Inclusion Free Cadmium Zinc Tellurium and Cadmium Tellurium Crystals and Associated Growth Method

Download or read book Inclusion Free Cadmium Zinc Tellurium and Cadmium Tellurium Crystals and Associated Growth Method written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The present disclosure provides systems and methods for crystal growth of cadmium zinc tellurium (CZT) and cadmium tellurium (CdTe) crystals with an inverted growth reactor chamber. The inverted growth reactor chamber enables growth of single, large, high purity CZT and CdTe crystals that can be used, for example, in X-ray and gamma detection, substrates for infrared detectors, or the like. The inverted growth reactor chamber enables reductions in the presence of Te inclusions, which are recognized as an important limiting factor in using CZT or CdTe as radiation detectors. The inverted growth reactor chamber can be utilized with existing crystal growth techniques such as the Bridgman crystal growth mechanism and the like. In an exemplary embodiment, the inverted growth reactor chamber is a U-shaped ampoule.

Book Simulation and Growth of Cadmium Zinc Telluride from Small Seeds by the Travelling Heater Method

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.

Book GROWTH OF CADMIUM ZINC TELLURIDE CRYSTALS BY CONTROLLED SEEDING CONTRACTLESS PHYSICAL VAPOR TRANSPORT NASA CR 204728 SEP 18 1997

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:

Book Study on Thermal Annealing of Cadmium Zinc Telluride CZT Crystals

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.

Book Development of Traveling Heater Method to Grow Cadmium Telluride CdTe Cadmium Zinc Telluride CZT Crystals

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:

Book Large Volume Single Crystal Growth of Cadmium Zinc Telluride with Minimal Secondary Phases for Room Temperature Radiation Detector Application

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.

Book Strategies and Challenges to Improve Single Crystal Yield and Detector Properties of Cadmium Zinc Telluirde that Is Telluride Grown Via Accelerated Crucible Rotation

Download or read book Strategies and Challenges to Improve Single Crystal Yield and Detector Properties of Cadmium Zinc Telluirde that Is Telluride Grown Via Accelerated Crucible Rotation written by Saketh Kakkireni and published by . This book was released on 2020 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solid-state radiation detection finds its applications in numerous fields ranging from nuclear medicine to astrophysics. Although Semiconductors offer better energy and spatial resolution than Scintillators, their market share is limited by the cost, availability and need for cryogenic cooling. Cadmium Zinc Telluride (CZT) is a compound semiconductor with attractive properties for compact device technology for detection of X-rays and Gamma-rays. Over the past few decades' numerous efforts are made to grow high-quality CZT, unfortunately to-date it's application is limited by large-scale production and cost. Poor thermo-physical properties of CZT coupled with no strong growth direction make it a challenge to achieve high yield of single crystalline material. Current industrial flux growth technique is inherently limited by slow growth rates and requires post-processing. The solution may be found in the Accelerated Crucible Rotation Technique (ACRT), where the crystal growth is achieved under a forced convective regime involving periodic rotation of the growth crucible. ACRT induced flow patterns can homogenize the melt thereby enabling faster growth rates and eliminate the need for post-processing. Our preliminary results, presented here, show that ACRT can reduce the production time by a factor of four. Additionally, the application of ACRT has provided the potential for scale up the growth process. Also discussed are challenges and future strategies in ACRT coupled CZT growth. Successful completion of this work will enable the use of CZT in the next generation imaging systems as well as provide a better foundation for understanding and implementing ACRT in other crystal growth systems. Successful seeding and superior detector resolutions are demonstrated.

Book SEEDED PHYSICAL VAPOR TRANSPORT OF CADMIUM ZINC TELLURIDE CRYSTALS GROWTH AND CHARACTERIZATION NASA TM 97 207738 JUN 1 1998

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:

Book Improved Techniques for the Growth of High Quality Cadmium Telluride Crystals

Download or read book Improved Techniques for the Growth of High Quality Cadmium Telluride Crystals written by R. S. Feigelson and published by . This book was released on 1985 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report summarizes two years' work as part of a multiyear program on improved techniques for the growth of high quality cadmium telluride crystals and represents one of the most comprehensive studies of melt growth and defect characterization in CdTe reported to date. Extensive melt growth studied were carried out using te vertical Bridgman method. Growth parameters were systematically varied in order to determine the influence of seed orientation, thermal environment, and growth rate on crystal quality. Growth interface shapes were revealed using autoradiographic dopant tracing methods. Melt thermal profiling was also carried out to further evaluate growth interface shapes. Controlled convex growth interface shapes were generated by using the heat exchanger method. By this means some improvement in grain structure of the typically polycrystalline boules was accomplished. Low frequency melt vibrations during growth were also observed to improve grain structure and reduce dislocation density. Extensive defect characterization was alos carried out using chemical etching methods, and later, synchrotron x-ray topography. Comparative studies of a broad selection of commercial CdTe substrates was carried out, and extensive defect structure was observed in all cases. Reduced dislocation densities and defect structures were accomplished using both low amplitude melt vibrations and doping with In 1IIC13. In the second case, solution hardening was assumed to be the mechanism responsible. For the case of melt vibration, the mechanism is not yet understood.

Book Research in Purification and Single Crystal Growth of II VI Compounds

Download or read book Research in Purification and Single Crystal Growth of II VI Compounds written by Lloyd W. Brown and published by . This book was released on 1965 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The preparation and purification of elemental cadmium by zone refining are described. A comparison of the emission and mass spectrographic results on the zoning of a doped cadmium test bar is presented. The syntheses of high purity cadmium sulfide, cadmium selenide, zinc sulfide, and zinc selenide by the direct reaction of their gaseous elemental constituents are discussed. Emission and mass spectrographic data on synthesized cadmium sulfide are compared. The syntheses of zinc telluride, mercuric sulfide, mercuric selenide, and mercuric telluride by the combination of the elements in the liquid phase are outlined. A method for preparing barium telluride by the reduction of barium tellurate is given. Special handling techniques and x-ray characterization of this material are presented. Crystal growth of cadmium sulfide, zinc sulfide, cadmium selenide, zinc selenide, and mixed crystals of zinc sulfide-zinc selenide from the melt in a high pressure furnace is discussed. Doping of melt grown crystals is described. A discussion of the crystal growth of cadmium sulfide, zinc sulfide, and cadmium oxide by vapor phase techniques is presented. (Author).

Book Research and Development on Single Crystal High Resistivity Cadmium Telluride for Use as a Gamma ray Spectrometer

Download or read book Research and Development on Single Crystal High Resistivity Cadmium Telluride for Use as a Gamma ray Spectrometer written by Kenneth R. Zanio and published by . This book was released on 1971 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: