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Study On Thermal Annealing Of Cadmium Zinc Telluride Czt Crystals
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Book Synopsis Study on Thermal Annealing of Cadmium Zinc Telluride (CZT) Crystals by :
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 Synopsis Post-Growth Annealing of Bridgman-grown CdZnTe and CdMnTe Crystals for Room-temperature Nuclear Radiation Detectors by :
Download or read book Post-Growth Annealing of Bridgman-grown CdZnTe and CdMnTe Crystals for Room-temperature Nuclear Radiation Detectors written by and published by . This book was released on 2015 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bridgman-grown cadmium zinc telluride (CdZnTe or CZT) and cadmium manganese telluride (CdMnTe or CMT) crystals often have Te inclusions that limit their performances as X-ray- and gamma-ray-detectors. We present here the results of post-growth thermal annealing aimed at reducing and eliminating Te inclusions in them. In a 2D analysis, we observed that the sizes of the Te inclusions declined to 92% during a 60-h annealing of CZT at 510 °C under Cd vapor. Further, tellurium inclusions were eliminated completely in CMT samples annealed at 570 °C in Cd vapor for 26 h, whilst their electrical resistivity fell by an order of 102. During the temperature-gradient annealing of CMT at 730 °C and an 18 °C/cm temperature gradient for 18 h in a vacuum of 10-5 mbar, we observed the diffusion of Te from the sample, causing a reduction in size of the Te inclusions. For CZT samples annealed at 700 °C in a 10 °C/cm temperature gradient, we observed the migration of Te inclusions from a low-temperature region to a high one at 0.022 [mu]m/s. During the temperature-gradient annealing of CZT in a vacuum of 10-5 mbar at 570 °C and 30 °C/cm for 18 h, some Te inclusions moved toward the high-temperature side of the wafer, while other inclusions of the same size, i.e., 10 μm in diameter, remained in the same position. These results show that the migration, diffusion, and reaction of Te with Cd in the matrix of CZT- and CMT-wafers are complex phenomena that depend on certain conditions.
Book Synopsis Annealing as Grown Large Volume CZT Single Crystals Increased Spectral Resolution by :
Download or read book Annealing as Grown Large Volume CZT Single Crystals Increased Spectral Resolution written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The spectroscopic performance of current large-volume Cadmium 10% Zinc Telluride, Cd{sub 0.9}Zn{sub 0.1}Te, (CZT) detectors is impaired by cumulative effect of tellurium precipitates (secondary phases) presented in CZT single-crystal grown by low-pressure Bridgman techniques(1). This statistical effect may limit the energy resolution of large-volume CZT detectors (typically 2-5% at 662 keV for 12-mm thick devices). The stochastic nature of the interaction prevents the use of any electronic or digital charge correction techniques without a significant reduction in the detector efficiency. This volume constraint hampers the utility of CZT since the detectors are inefficient at detecting photons>1MeV and/or in low fluency situations. During the project, seven runs CZT ingots have been grown, in these ingots the indium dopant concentrations have been changed in the range between 0.5ppm to 6ppm. The I-R mapping imaging method has been employed to study the Te-precipitates. The Teprecipitates in as-grown CZT wafers, and after annealing wafers have been systematically studied by using I-R mapping system (home installed, resolution of 1.5 [mu]m). We employed our I-R standard annealing CZT (Zn=4%) procedure or two-steps annealing into radiation CZT (Zn=10%), we achieved the 'non'-Te precipitates (size 1 [mu]m) CZT n+-type with resistivity 109−1° [Omega]-cm. We believe that the Te-precipitates are the p-type defects, its reducing number causes the CZT became n+-type, therefore we varied or reduced the indium dapant concentration during the growth and changed the Te-precipitates size and density by using different Cd-temperature and different annealing procedures. We have made the comparisons among Te-precipitates size, density and Indium dopant concentrations, and we found that the CZT with smaller size of Te-precipitates is suitable for radiation uses but non-Te precipitates is impossible to be used in the radiation detectors, because the CZT would became un-dopant or 'intrinsic' with non radiation affection (we have studied before). We used 3 weeks annealing time for 3-5 mm thickness CZT wafres, if the thickness increased to 10-15mm, the annealing time would be increased to many months, which is very unpractical and very difficult to control the CZT property. We have obtained as-grown CZT by using adding the extra Cd before growth, which showed the smaller size of Te-precipitates and excellent radiation performance. These CZT has very high [mu][tau](e)>1 x 10−2cm2/V, [rho]> 2 x 101° [Omega]-cm, and the thickness could be up to 80-100mm. The energy resolution of the detector (thickness>10mm) at 662 keV is about 1.2% without any correction (2) and according to Aquila, the 0.5-0.8% resolution at 662 keV would be expected by using appropriated electronic correction.
Book Synopsis Development of CdZnTe Radiation Detectors by :
Download or read book Development of CdZnTe Radiation Detectors written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Cadmium Zinc Telluride (CdZnTe or CZT) is a very attractive material for room-temperature semiconductor detectors because of its wide band-gap and high atomic number. Despite these advantages, CZT still presents some material limitations and poor hole mobility. In the past decade most of the developing CZT detectors focused on designing different electrode configurations, mainly to minimize the deleterious effect due to the poor hole mobility. A few different electrode geometries were designed and fabricated, such as pixelated anodes and Frisch-grid detectors developed at Brookhaven National Lab (BNL). However, crystal defects in CZT materials still limit the yield of detector-grade crystals, and, in general, dominate the detector's performance. In the past few years, our group's research extended to characterizing the CZT materials at the micro-scale, and to correlating crystal defects with the detector's performance. We built a set of unique tools for this purpose, including infrared (IR) transmission microscopy, X-ray micro-scale mapping using synchrotron light source, X-ray transmission- and reflection-topography, current deep level transient spectroscopy (I-DLTS), and photoluminescence measurements. Our most recent work on CZT detectors was directed towards detailing various crystal defects, studying the internal electrical field, and delineating the effects of thermal annealing on improving the material properties. In this paper, we report our most recent results.
Book Synopsis Development of Traveling Heater Method to Grow Cadmium Telluride (CdTe)/Cadmium Zinc Telluride (CZT) Crystals by : Manchanahalli S. Rohan Rao
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 Synopsis Developments in Cadmium Zinc Telluride Crystal Growth, Sample Preparation and Characterisation [sic] Techniques by : Amlan Datta
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:
Book Synopsis Induced Positron Annihiliation Investigation of Cadmium Zinc Telluride Crystal Microstructures by : D. W. Akers
Download or read book Induced Positron Annihiliation Investigation of Cadmium Zinc Telluride Crystal Microstructures written by D. W. Akers and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Cadmium-Zinc-Telluride (CZT) crystals are used in semiconductor radiation detectors for the detection of x-ray and gamma radiation. However, production of detector grade crystals is difficult as small variations in compositional uniformity and primarily the zinc content can significantly affect the ability of the CZT crystal to function as a radiation detector. Currently there are no known nondestructive methods that can be used to identify detector grade crystals. The current test method is to fabricate and test the detector to determine if the crystal is sufficiently uniform and of the correct composition to be considered a detector grade crystal. Consequently, nondestructive detection methods are needed to identify detector grade crystals prior to the fabrication process. The purpose of this feasibility study was to perform a preliminary assessment of the ability of several new, nondestructive technologies based on Induced Positron Annihilation (IPA) to determine if detector grade CZT crystals can be identified. Results of measurements performed on specimens from Fisk University and EV Products, Inc. indicate that both the near surface Distributed Source Positron Annihilation (up to 3 mm penetration) and the volumetric Photon Induced Positron Annihilation methods may be suitable for determining CZT crystal quality. Further work on CZT crystals with a broader range of compositions and detector characteristics is needed to provide a well defined, calibrated, method for assessing CZT crystal quality.
Book Synopsis Photoluminescence Characterization of Cadmium Zinc Telluride by : Mohamed Alshal
Download or read book Photoluminescence Characterization of Cadmium Zinc Telluride written by Mohamed Alshal and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The demand for wide bandgap semiconductors for radiation detector applications has significantly increased in recent years due to an ever-growing need for safeguard measures and medical imaging systems amongst other applications. The need for these devices to be portable and efficient, and to operate at room temperature is important for practical applications. For radiation detectors, the semiconductor materials are mainly required to have an optimal energy gap, high average atomic number, good electrical resistivity and charge transport properties as well as purity and homogeneity. Cadmium zinc telluride (CZT) distinctly stands out among the other choices of semiconductor materials for radiation detector applications, due to its attractive material properties and the room temperature operation possibility. A tremendous amount of research is being conducted to improve CZT technology and its implementation into more commercial systems. Applications of CZT detector technology in national security, high energy physics, nuclear spectroscopy, and medical imaging systems are of special interests. However, CZT devices still face challenges that need to be understood and overcome in order to have more efficient radiation detector systems. One such challenge lies in the understanding of the surfaces of CZT detectors and surface recombination effects on charge transport, charge collection efficiency, and detector performance. Another common issue is the degradation of CZT detectors due to the presence of defects which can act as traps for the charge carriers and cause incomplete charge collection from the detectors. Thus, a major challenge is that, the commercial CZT crystals have large concentrations of defects and impurities that need to be characterized, and their effects on the detector performance should be studied. Photoluminescence (PL) spectroscopy is a sensitive, non-contact and non-destructive method, suitable to characterize lower concentrations of point defects, such as substitutional impurities (donors, acceptors) and native defects in CZT crystals. A PL spectrum provides information regarding the defect nature of the crystal by determining the presence and the type of vacancies, interstitials, and impurities in the lattice. The main objective of this thesis is to address the presence of the defects in CZT crystals, identify their types, and study their roles in the performance of x-ray radiation detectors using PL spectroscopy. Additionally, using PL method and different excitation sources including UV excitation, this thesis studies the surface of CZT samples and investigates the PL signature of the surface oxide of the samples, in an effort to optimize the surface processing and thereby improve CZT detector performance.
Book Synopsis Material Properties of Large-volume Cadmium Zinc Telluride Crystals and Their Relationship to Nuclear Detector Performance by :
Download or read book Material Properties of Large-volume Cadmium Zinc Telluride Crystals and Their Relationship to Nuclear Detector Performance written by and published by . This book was released on 1997 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The material showing the greatest promise today for production of large-volume gamma-ray spectrometers operable at room temperature is cadmium zinc telluride (CZT). Unfortunately, because of deficiencies in the quality of the present material, high-resolution CZT spectrometers have thus far been limited to relatively small dimensions, which makes them inefficient at detecting high photon energies and ineffective for weak radiation signals except in near proximity. To exploit CZT fully, it will be necessary to make substantial improvements in the material quality. Improving the material involves advances in the purity, crystallinity, and control of the electrical compensation mechanism. Sandia National Laboratories, California, in close collaboration with US industry and academia, has initiated efforts to develop a detailed understanding of the underlying material problems limiting the performance of large volume gamma-ray spectrometers and to overcome them through appropriate corrections therein. A variety of analytical and numerical techniques are employed to quantify impurities, compositional and stoichiometric variations, crystallinity, strain, bulk and surface defect states, carrier mobilities and lifetimes, electric field distributions, and contact chemistry. Data from these measurements are correlated with spatial maps of the gamma-ray and alpha particle spectroscopic response to determine improvements in the material purification, crystal growth, detector fabrication, and surface passivation procedures. The results of several analytical techniques will be discussed. The intended accomplishment of this work is to develop a low-cost, high-efficiency CZT spectrometer with an active volume of 5 cm3 and energy resolution of 1--2% (at 662 keV), which would give the US a new field capability for screening radioactive substances.
Book Synopsis Optimization of Cadmium Zinc Telluride Crystal Growth for Room Temperature Radiation Detectors by : Kelly Allan Jones
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:
Book Synopsis Proceedings of the ... National Conference on Undergraduate Research by :
Download or read book Proceedings of the ... National Conference on Undergraduate Research written by and published by . This book was released on 1997 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Global Modeling of Bulk Crystal Growth of Cadmium Zinc Telluride in Industrial VB/VGF Systems by : Arun Pandy
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:
Book Synopsis Advanced Materials for Radiation Detection by : Krzysztof (Kris) Iniewski
Download or read book Advanced Materials for Radiation Detection written by Krzysztof (Kris) Iniewski and published by Springer Nature. This book was released on 2021-08-05 with total page 357 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers readers an overview of some of the most recent advances in the field of advanced materials used for gamma and X-ray imaging. Coverage includes both technology and applications, with an in-depth review of the research topics from leading specialists in the field. Emphasis is on high-Z materials like CdTe, CZT and GaAs, as well as perovskite crystals, since they offer the best implementation possibilities for direct conversion X-ray detectors. Authors discuss material challenges, detector operation physics and technology and readout integrated circuits required to detect signals processes by high-Z sensors.
Book Synopsis Cadmium Zinc Telluride Spectral Modeling by :
Download or read book Cadmium Zinc Telluride Spectral Modeling written by and published by . This book was released on 1998 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cadmium Zinc Telluride (CZT) detectors are the highest resolution room-temperature gamma ray detectors available for isotopic analysis. As with germanium detectors, accurate isotopic analysis using the spectra requires peak deconvolution. The CZT peak shapes are asymmetric, with a long low energy tail. The asymmetry is a result of the physics of the electron/hole transport in the semiconductor. An accurate model of the physics of the electron/hole transport through an electric field will allow the parameterization of the peak shapes as a function of energy. In turn this leads to the ability to perform accurate spectral deconvolution and therefore accurate isotopic analysis. The model and the peak-shape parameterization as a function of energy will be presented.
Book Synopsis Characterization of Te Secondary Phases in Cadmium Zinc Telluride Using IR Transmission Microscopy by : W. Gitau Munge
Download or read book Characterization of Te Secondary Phases in Cadmium Zinc Telluride Using IR Transmission Microscopy written by W. Gitau Munge and published by . This book was released on 2010 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Defect Characterization in 4% Cadmium Zinc Telluride Semiconductors by : Silvia I. Penkova
Download or read book Defect Characterization in 4% Cadmium Zinc Telluride Semiconductors written by Silvia I. Penkova and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a characterization study of Cadmium Zinc Telluride with a 4% Zinc molar concentration using five different techniques. Three of the characterization methods - X-ray diffraction (XRD), transmission electron microscopy (TEM) and wet chemical etching - were used to study the atomic arrangement of the lattice and the type of defects in the material. On the other hand, the other two methods - photoluminescence (PL) and the Hall Effect - provided information about the electronic properties of the material and identified the electronic signatures of the defects present. This thesis study applied these five methods to 29 samples with the [111] and [211] crystal orientations. XRD was used to calculate the Zn concentration and the atomic spacing of the samples. TEM allowed to map the crystal structure using Kikuchi diffraction and to calculate the variation of the local lattice constant. This showed that the sample was under strain. A CBED imaging condition producing HOLZ lines allowed for qualitatively imaging the strain field in the crystal and contrast phase imaging showed stacking faults and dislocations present in the lattice. Next, wet chemical etching - using Nakagawa and Everson solutions - revealed several different types of etch pits were present on the material's surface and provided a value for the etch pit density (EPD). PL at room temperature was used to calculate the Zn concentration and to produce contour maps of the samples showing the variation in Zn. Low temperature PL was used to conduct intensity and thermal studies of the material providing information about the type of emission (donor-acceptor pair, free exciton or excitonic) and the activating energies. This information was used to assign the peaks seen in the PL spectrum at 8K. Lastly, the Hall Effect experiment was used to calculate the resistivity and the mobility of carriers, i.e., electrons and holes, of the samples. The last stage of the project was to seek correlations between the data obtained during the five characterization techniques. Correlations were noted between the XRD FWHM broadening and the EPD, the disturbances in the atomic lattice and the defect band broadening and a summary of all the values calculated during the project was provided. Overall this project provided a very thorough study of 4% CZT.
Book Synopsis International Research in Engineering Sciences VIII by : Tayfun Soysal
Download or read book International Research in Engineering Sciences VIII written by Tayfun Soysal and published by EĞİTİM YAYINEVİ. This book was released on 2024-05-01 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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