DOCSLIB.ORG

Two Cadmium Zinc Telluride (CZT) Semiconductor Detectors, a Lacl3(Ce) Scintillator, and an Nai(Tl) Scintillator

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Two Cadmium Zinc Telluride (CZT) Semiconductor Detectors, a Lacl3(Ce) Scintillator, and an Nai(Tl) Scintillator Performance comparison of four compact room- temperature detectors – two cadmium zinc telluride (CZT) semiconductor detectors, a LaCl3(Ce) scintillator, and an NaI(Tl) scintillator John K. Hartwell, Member IEEE, Robert J. Gehrke, and Michael E. Mc Ilwain measurement scenarios where portability, compact design, Abstract— The performance characteristics of four compact, and freedom from cryogenics are primary considerations. room-temperature detectors – two scintillators and two A recent publication provided performance comparison semiconductor detectors – were studied. All are commercially- data on three detectors including a ∅10 cm X 10 cm NaI(Tl), available detectors. The two scintillators were a ∅13 mm X a ∅55 mm X 54 mm HPGe detector, and a ∅9 mm X 2 mm 13 mm lanthanum chloride [LaCl3(Ce)] detector and a ∅25 mm X 25 mm sodium iodide [NaI(Tl)] detector. The two CdTe detector [1]. Our work, reported in this paper, provides semiconductor detectors were a 10 mm X 10 mm X 3 mm complimentary assessment data on a different suite of four cadmium zinc telluride (CZT) detector with a coplanar gridded highly portable detectors, including work with the promising anode and a 5 mm X 5 mm X 5 mm CZT detector with an new scintillator LaCl3(Ce). extended cathode. The efficiency, resolution, and peak shape of these devices are compared. Since LaCl (Ce) is a relatively new 3 II. EXPERIMENTAL METHOD commercial scintillator material, additional information on the performance of this detector is presented. Specifically, the The electronics system used for these evaluations consisted impact of naturally-occurring radioactive 138La and additional of a preamplifier, a linear amplifier (Tennelec TC244 or Ortec contamination from alpha-emitting radionuclides on the 460), and an multichannel analyzer (Amptek MCA8000A) background measured with this detector are discussed. along with the required high voltage bias supply (ORTEC 556 Index Terms— Gamma-ray spectroscopy detectors, or ORTEC 459). Amplifier pulse shaping times and system LaCl3(Ce) scintillation detectors, Room temperature semiconductor detectors gains were adjusted to match the requirements of the detector and the desired peak positioning. All spectra were stored in I. INTRODUCTION 2048 channels. While High Purity Germanium (HPGe) detectors, with their A set of three sealed point sources were used for this evaluation. The source radionuclides, their activities and unexcelled gamma-ray energy resolution, are often the best 57 choice for gamma-ray spectroscopy applications; the estimated total uncertainties on 01-January-04 were Co ± 60 ± 137 ± requirement for cryogenic cooling during operation (1.95 0.09 kBq), Co (117 5 kBq), and Cs (360 11 kBq). ± complicates their use in certain applications. This work Source-to-detector distances were 10.0 0.2 cm unless compares the detection efficiency and resolution capabilities otherwise noted. The system gain for each detector was of four alternative gamma-ray spectrometric detectors that adjusted to position like peaks in the same channel. Thus the 57 operate at room temperature. Although none of these units spectra of Co taken with all four detectors had the 122 keV 137 provides the combination of resolution and detection peak in channel 368 ± 3, the Cs 662 keV peak in channel efficiency afforded by a HPGe, they have performance 976 ± 5 and the 60Co 1332 keV peak in channel 1737 ± 3. features that make them attractive for certain radiation Two cadmium zinc telluride (CZT) detectors were evaluated in this study. The first (designated detector C5) was a 5 mm X 5 mm X 5 mm (125 mm3) crystal obtained from eV Products. This detector is a quasi-hemispherical device with a Manuscript received 24-Sept.-2004. Prepared for the U.S. Department of Energy Through the INEEL LDRD Program Under DOE Idaho Operations full area anode and extended cathode that provides improved Office Contract DE-AC07-99ID13727. charge collection characteristics and thus improved resolution J. K. Hartwell is with the Idaho National Engineering and Environmental and peak shape relative to a pure planar design [2]. The Laboratory (INEEL), PO Box 1625-2114 Idaho Falls, ID 83415-2114. Phone: 208-526-9366; Fax: 208-526-9267; e-mail [email protected] detector is packaged along with a hybrid preamplifier in an R. J. Gehrke and M. E. Mc Ilwain are also with the INEEL. 0-7803-8701-5/04/$20.00 (C) 2004 IEEE integral package ∅12 mm by 89 mm. During testing the The base was an Ortec Model 266 and the AC-coupled detector bias voltage was +1000 V. The amplifier shaping dynode output signal was used directly as input to the TC244 time was 0.375 µsec. Testing determined that the face of the amplifier. The high voltage was set to +780 V. The amplifier detector was 13 ± 2 mm back from the detector end cap. Thus, shaping time was 1.5 µsec. to achieve a source-to-detector distance of 10.0 cm, the 57Co The spectra were acquired using the Amptek program and 137Cs sources were positioned 8.7 cm from the detector PMCA Version 2.01 specifically provided for control of the C5 end cap. The 60Co source was counted at a 5 cm source-to- 8000A Pocket MCA. Most net photopeak areas were detector distance or 3.7 cm from the end cap; and the data computed using a simple region-of-interest summation with a corrected to a source-to-detector distance of 10 cm using an stepped background subtraction, and photopeak resolution inverse square assumption. values (FWHM) were computed using analytical interpolation The second CZT detector (designated CP) was a 10 mm X of the channel contents, an approach that provides a better and 10 mm X 3 mm (300 mm3) detector obtained from Spire more consistent measure of the overall peak widths when Corporation. This crystal was equipped with a coplanar- photopeak shapes are non-Gaussian than do FWHM values gridded anode to significantly improve the unit’s resolution derived from peak fitting results. An exception to this performance [3]. The detector was packaged along with the approach was for the area calculation of the 122 keV peak of 57 required preamplifiers and analog subtraction circuit in a Co in the spectra acquired with the two scintillation ∅3.2 cm by 13 cm unit. The detector was operated with a bias detectors. The resolution of the L2 and N1 detectors was voltage of – 600 V and a grid bias of – 60 V. The amplifier insufficient to resolve the 122 keV and the 136 keV peaks. shaping time was 0.375 µsec. All sources were counted at a Consequently, the area of the 122 keV peak in these spectra distance of 9 cm from the detector end cap. However, testing was computed by non-linear least squares fitting of the 122- indicated that the detector face was located 1.8 ± 0.4 cm back 136 keV peak region as a doublet with Gaussian functions and from the anodized aluminum end cap. Consequently, sources a step background. counted at a source-to-end cap distance of 9 cm were actually 10.8 ± 0.4 cm from the detector. The results for this detector III. RESULTS AND DISCUSSION presented in this report have been adjusted to a source-to- detector distance of 10 cm by the inverse square law. Table 1 compares the measured efficiency in counts per Two scintillation detectors were included in this evaluation emitted gamma-ray at a 10 cm source-to-detector distance, – a LaCl3(Ce) and a NaI(Tl) detector. The LaCl3(Ce) detector and the resolution at half maximum height (FWHM) and the (designated L2) was a ∅13 mm X 13 mm (1.7 cm3) crystal of full width at one-tenth maximum height (FWTM) of the four LaCl3 with 10% Ce. This scintillation material is reported to detectors for the major peaks of the three radionuclides have an excellent combination of scintillation light output and counted. All uncertainties are quoted at one estimated resolution [4]. The detector was an integral unit coupled to a standard deviation. Photonis XP1911 photomultiplier tube with a dividing Additionally, Figure 1 plots the spectral region around the 137 network configured for positive high voltage. A high voltage 662 keV peak for the Cs point source at 10 cm from each setting of +800 V was used. Some spectra were acquired detector. Not only does this figure illustrate the comparative using a delay line amplifier (ORTEC 460) and a 0.25 µsec efficiency and resolution of the detectors tested, it highlights shaping time. Other spectra used the TC244 amplifier and a the significant peak shape differences noted with certain of shaping time of either 0.375 or 6 µsec. All sources were these detectors. counted at a source-to-detector distance of 10 cm. Only the NaI(Tl) detector N1 performed exactly as In addition to the source spectra acquired, a number of expected. Although the N1 resolution performance was the background spectra were taken with the LaCl3(Ce) detector. poorest of the four tested detectors, it exhibited the expected Background spectra were of particular interest with this photopeak efficiency and peak shape. Details regarding the detector for two reasons. First, Lanthanum has a naturally- performance of the other three detectors are discussed below. occurring radioactive isotope, 138La (1.05X1011 year half-life) 3 present in an abundance of about 0.09% in natural La and we A. The 125 mm CZT detector (C5) wanted to assess the effect of this 138La on the crystal The least efficient (and most compact) of the detectors 3 background. Second, during preliminary work with this studied is the 125 mm eV Products detector (C5). This unit scintillator, we and another researcher [5] noted a puzzling set incorporates what the manufacturer calls CAPturea technology of broad peaks in the background at energies between about that uses a full area anode and a cathode contact plated on the 1500 and 3000 keV.
Load more

Recommended publications
  • Progress in the Development of Cdte and Cdznte Semiconductor Radiation Detectors for Astrophysical and Medical Applications
    Sensors 2009, 9, 3491-3526; doi:10.3390/s90503491 OPEN ACCESS sensors ISSN 1424-8220 www.mdpi.com/journal/sensors Review Progress in the Development of CdTe and CdZnTe Semiconductor Radiation Detectors for Astrophysical and Medical Applications Stefano Del Sordo 1,*, Leonardo Abbene 1,2,*, Ezio Caroli 3, Anna Maria Mancini 4, Andrea Zappettini 5 and Pietro Ubertini 6 1 INAF/IASF Palermo, Via Ugo La Malfa 153, 90146 Palermo, Italy 2 Dipartimento di Fisica e Tecnologie Relative, Università di Palermo,Viale delle Scienze, 90128 Palermo, Italy 3 INAF/IASF Bologna, Via Gobetti 101, 40129 Bologna, Italy; E-Mail: [email protected] (E.C.) 4 Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Via Arnesano, 73100 Lecce, Italy; E-Mail: [email protected] (A.M.M.) 5 IMEM-CNR, Parco Area delle Scienze 37/A, 43100 Parma, Italy; E-Mail: [email protected] (A.Z.) 6 INAF/IASF Roma, Via del Fosso del Cavaliere 100, 00133 Roma, Italy; E-Mail: [email protected] (P.U.) * Authors to whom correspondence should be addressed; E-Mails: [email protected]; (S.D.S.); [email protected] (L.A.); Tel. +39-091-6809563; Fax: +39-091-6882258 (S.D.S.); Tel. +39-091-6615053; Fax: +39-091-6615063 (L.A.) Received: 26 March 2009; in revised form: 5 May 2009 / Accepted: 8 May 2009 / Published: 12 May 2009 Abstract: Over the last decade, cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) wide band gap semiconductors have attracted increasing interest as X-ray and gamma ray detectors.
    [Show full text]
  • Characterization of Cadmium Zinc Telluride Solar Cells by RF Sputtering Senthilnathan Subramanian University of South Florida
    University of South Florida Scholar Commons Graduate Theses and Dissertations Graduate School 6-24-2004 Characterization of Cadmium Zinc Telluride Solar Cells by RF Sputtering Senthilnathan Subramanian University of South Florida Follow this and additional works at: https://scholarcommons.usf.edu/etd Part of the American Studies Commons Scholar Commons Citation Subramanian, Senthilnathan, "Characterization of Cadmium Zinc Telluride Solar Cells by RF Sputtering" (2004). Graduate Theses and Dissertations. https://scholarcommons.usf.edu/etd/1261 This Thesis is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. Characterization of Cadmium Zinc Telluride Solar Cells by RF Sputtering by Senthilnathan Subramanian A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering Department of Electrical Engineering College of Engineering University of South Florida Major Professor: Christos S. Ferekides, Ph.D. Don L. Morel, Ph.D. Yun L. Choiu, Ph.D Date of Approval: June 29, 2004 Keywords: czt, thin films, wide bandgap semiconductors, tandem solar cells © Copyright 2004 , Senthilnathan Subramanian DEDICATION This thesis is dedicated to my family and friends for their love and support. ACKNOWLEDGEMENT I would like to express my gratitude to my Major Professor Dr. Chris Ferekides for his invaluable guidance and support during the course of this work. He has been a great source of inspiration during my work here. I also thank Dr.Don L. Morel and Dr.
    [Show full text]
  • Fabrication of Small-Pixel Cdznte Sensors and Characterization with X-Rays
    sensors Article Fabrication of Small-Pixel CdZnTe Sensors and Characterization with X-rays Stergios Tsigaridas 1,∗,† , Silvia Zanettini 2 , Manuele Bettelli 3 , Nicola Sarzi Amadè 3 , Davide Calestani 3 , Cyril Ponchut 1 and Andrea Zappettini 3 1 European Synchrotron Radiation Facility (ESRF), 71 Avenue des Martyrs, F-38043 Grenoble, France; [email protected] 2 Due2lab s.r.l., via Paolo Borsellino 2, 42019 Scandiano, Italy; [email protected] 3 IMEM-CNR, Istituto Materiali per l’Elettronica e il Magnetismo, Consiglio Nazionale delle Ricerche, Parco Area delle Scienze 37/A, 43124 Parma, Italy; [email protected] (M.B.); [email protected] (N.S.A.); [email protected] (D.C.); [email protected] (A.Z.) * Correspondence: [email protected] † Current address: TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada. Abstract: Over the past few years, sensors made from high-Z compound semiconductors have attracted quite some attention for use in applications which require the direct detection of X-rays in the energy range 30–100 keV. One of the candidate materials with promising properties is cadmium zinc telluride (CdZnTe). In the context of this article, we have developed pixelated sensors from CdZnTe crystals grown by Boron oxide encapsulated vertical Bridgman technique. We demonstrate the successful fabrication of CdZnTe pixel sensors with a fine pitch of 55 µm and thickness of 1 mm and 2 mm. The sensors were bonded on Timepix readout chips to evaluate their response to X-rays Citation: Tsigaridas, S.; Zanettini, S.; provided by conventional sources. Despite the issues related to single-chip fabrication procedure, Bettelli, M.; Sarzi Amadè, N.; reasonable uniformity was achieved along with low leakage current values at room temperature.
    [Show full text]
  • Cd,-,Zn,Te Materials
    Source of Acquisition NASA Goddard Space Flight Center Temperature Evolution of Excitonic Absorptions in Cd,-,Zn,Te Materials Manuel A. Quijada and Ross Henry Goddard Space Flight Center, Code 551, Greenbelt, MD 20771, USA ABSTRACT The studies consist of measuring the frequency dependent transmittance (T) and reflectance (R) above and below the optical band-gap in the W/Visible and infrared frequency ranges for Cdl-,Zn,Te materials for x=O and XI-0.04. Measurements were also done in the temperature range from 5 to 300 K. The results show that the optical gap near 1.49 eV at 300 K increases to 1.62 eV at 5 K. Finally, we observe sharp absorption peaks near this gap energy at low temperatures. The close proximity of these peaks to the optical transition threshold suggests that they originate from the creation of bound electron-hole pairs or excitons. The decay of these excitonic absorptions may contribute to a photoluminescence and transient background response of these back-illuminated HgCdTe CCD detectors. Keywords: Keywords: CdZnTe, UV/Vis infrared, transmittance, reflectance, semiconducting gap, photolumi- nescence, exciton 1. INTRODUCTION The ternary compound Cdl-,Zn,Te (CdZnTe) is a semiconducting alloy that is widely used as a base material for x-ray and infrared detectors. In particular, single crystals of CdZnTe wafers are the principal material on which HgCdTe epitaxial layers have been recently grown for the fabrication of infrared sensors on lattice matched CdZnTe substrate.l This has been possible due to recent advances through use of new detector growth technologies2 which involve p/n double layer planar heterostructure arrays grown by Molecular Beam Epitaxy (MBE).
    [Show full text]
  • Photoluminescence Study of Cadmium Zinc Telluride
    Graduate Theses, Dissertations, and Problem Reports 2001 Photoluminescence study of cadmium zinc telluride Swati Jain West Virginia University Follow this and additional works at: https://researchrepository.wvu.edu/etd Recommended Citation Jain, Swati, "Photoluminescence study of cadmium zinc telluride" (2001). Graduate Theses, Dissertations, and Problem Reports. 1252. https://researchrepository.wvu.edu/etd/1252 This Thesis is protected by copyright and/or related rights. It has been brought to you by the The Research Repository @ WVU with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you must obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in WVU Graduate Theses, Dissertations, and Problem Reports collection by an authorized administrator of The Research Repository @ WVU. For more information, please contact [email protected]. PHOTOLUMINESCENCE STUDY OF CADMIUM ZINC TELLURIDE Swati Jain Thesis submitted to the Eberly College of Arts and Sciences at West Virginia University in partial fulfillment of the requirements for the degree of Master of Science in Physics Nancy C. Giles, Ph.D., Chair Larry E. Halliburton, Ph.D. Mohindar S. Seehra, Ph.D. Department of Physics Morgantown, West Virginia 2001 Keywords: Photoluminescence, PL, CdZnTe, CZT, Cd1-xZnxTe ABSTRACT PHOTOLUMINESCENCE STUDY OF CADMIUM ZINC TELLURIDE SWATI JAIN In this thesis, I present a detailed study of Cd1-xZnxTe crystals with 0 ≤ x ≤ 0.14 using photoluminescence (PL) spectroscopy.
    [Show full text]
  • Cadmiumzinc Telluride High Resolution Detector Technology
    Invited Paper CadmiumZinc Telluride High Resolution Detector Technology Arnold Burger, Henry Chen, Kaushik Chattopadhyay, Jean-Olivier Ndap and Stephen U. Egarievwe, Center for Photonic Materials and Devices, Department of Physics Nashville, TN 37208-3051, U. S. A. and R. B. James, Advanced Electronics Manufacturing Technologies Department, Sandia National Laboratories, Livermore, CA 94550 ABSTRACT Electrode contacting on semiconductor radiation detectors has been a topic of active interest in many recent investigations. Research activities have focused on the morphology and chemistry of modified surfaces using sophisticated preparation techniques and employing characterization methods that are able to discriminate between surface and bulk effects. From an applied point of view, the detector fabrication technology involves a series of fabrication steps which can be optimized. Results of an ongoing effort to improve the performance of high resolution Cd,Zn1Te (CZT) spectrometers by addressing wafer surface preparation, electrode deposition and contact passivation are described.. Keywords: Cadmium zinc telluride, detector fabrication, contacts, surface preparation 1. INTRODUCTION There is presently a widespread need for room temperature gamma and X-ray imaging capability for both medical and industrial applications. Solid state CZT arrays offer the possibility of reducing the weight of existing nuclear medicine cameras based on scintillators and photomultiplier. CZT combines the room temperature operation with the energy resolution that approaches that ofthe cryogenically cooled Ge and Si detectors. However, CZT detectors are still in very limited use, mainly due to the limited availability oflow price and defect free material. Recently, studies aimed at a better understanding of the electric contact formation process were performed and it was shown that in many cases, in particular when high resolution, low active volume detectors, the performance of the detectors is limited by surface preparation, contacting and device passivation.
    [Show full text]
  • The Cadmium Zinc Telluride Imager on Astrosat
    J. Astrophys. Astr. (June 2017) 38:31 © Indian Academy of Sciences DOI 10.1007/s12036-017-9447-8 Review The Cadmium Zinc Telluride Imager on AstroSat V. BHALERAO1, D. BHATTACHARYA1, A. VIBHUTE1,P.PAWAR1,2,A.R.RAO3,∗, M. K. HINGAR3, RAKESH KHANNA3,A.P.K.KUTTY3, J. P. MALKAR3,M.H.PATIL3, Y. K. ARORA3, S. SINHA3,P.PRIYA4, ESSY SAMUEL4, S. SREEKUMAR4, P. VINOD4, N. P. S. MITHUN5, S. V. VADAWALE5, N. VAGSHETTE1,5, K. H. NAVALGUND6, K. S. SARMA6, R. PANDIYAN6, S. SEETHA6 and K. SUBBARAO6 1Inter University Centre for Astronomy and Astrophysics, Pune 411 007, India. 2S. R. T. M. University, Nanded 431 606, India. 3Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India. 4Vikram Sarabhai Space Centre, Thiruvananthapuram 695 022, India. 5Physical Research Laboratory, Ahmedabad 380 009, India. 6ISRO Satellite Centre, Bangalore 560 017, India. ∗Corresponding author. E-mail: [email protected] MS received 11 August 2016; accepted 29 December 2016; published online 19 June 2017 Abstract. The Cadmium Zinc Telluride Imager (CZTI) is a high energy, wide-field imaging instrument on AstroSat. CZTI’s namesake Cadmium Zinc Telluride detectors cover an energy range from 20 keV to > 200 keV, with 11% energy resolution at 60 keV. The coded aperture mask attains an angular resolution of 17 over a 4.6◦× 4.6◦ (FWHM) field-of-view. CZTI functions as an open detector above 100 keV, continuously sensitive to GRBs and other transients in about 30% of the sky. The pixellated detectors are sensitive to polarization above ∼100 keV, with exciting possibilities for polarization studies of transients and bright persistent sources.
    [Show full text]
  • Backgrounds in Cadmium Zinc Telluride (Czt) Gamma-Ray Spectrometers for Planetary Science
    43rd Lunar and Planetary Science Conference (2012) 1284.pdf BACKGROUNDS IN CADMIUM ZINC TELLURIDE (CZT) GAMMA-RAY SPECTROMETERS FOR PLANETARY SCIENCE. R. C. Reedy1, T. H. Prettyman1, and N. Yamashita1, 1Planetary Science Institute, Suite 106, 1700 E Fort Lowell, Tucson, AZ 85719. <reedy@ psi.edu>. Summary: The gamma rays made by space ener- capture of an orbiting electron or by an isomeric (or getic particles in CdZnTe detectors, such as those on internal) transition in one nucleus [2]. the NASA Dawn Mission, are listed and discussed. Production of prompt gamma rays during events Introduction: Gamma-ray detectors in space have with high fluxes of solar protons was not considered backgrounds in their spectra because of cosmic-ray because the energy loss of the proton in the detector interactions with the detector materials. A good under- will sum with most gamma rays. standing of all those backgrounds, especially discrete- Being a minor component, only the strongest gam- energy peaks, in a gamma-ray spectrometer (GRS) is ma rays are given for Zn. needed to correctly analyze the measured gamma-ray Peaks inside CZT Detectors: Almost all of the spectra from a planetary object of interest. Most back- peaks made in CZT by these gamma rays (individually grounds contribute to the continuum, but some are in or by summing) are <2 MeV, and therefore could be at peaks. Some of these peaks could possibly interfere energies of many gamma rays used to map elements. with gamma rays used to determine elemental compo- Prompt neutron-induced reactions: The main sition of an object.
    [Show full text]
  • Advances in Cdzntese for Radiation Detector Applications
    Article Advances in CdZnTeSe for Radiation Detector Applications Utpal N. Roy 1,*, Giuseppe S. Camarda 2, Yonggang Cui 2 and Ralph B. James 1 1 Savannah River National Laboratory, Aiken, SC 29808, USA; [email protected] 2 Brookhaven National Laboratory, Upton, NY 11973, USA; [email protected] (G.S.C.); [email protected] (Y.C.) * Correspondence: [email protected] Simple Summary: Cadmium-zinc-telluride is the most important semiconductor material today for room temperature gamma-ray detector applications. The radiation detectors are widely used for medical imaging, homeland security, and X- and gamma-ray astronomy. However, the material has longstanding technological problems. Despite significant improvements over the past 3 decades, the technology still suffers from major detrimental defects such as a high concentration of tellurium inclusions and sub-grain boundary network/dislocation walls, which adversely impact the yield of high-quality detectors fabricated from the crystals. To address these challenges, selenium was added to the cadmium zinc telluride matrix. The Se addition was found to have a profound effect to reduce the deleterious defects in the crystals. The resulting cadmium-zinc-telluride-selenide material was found to be free from a sub-grain boundary network with reduced tellurium inclusions. Thus, cadmium zinc telluride selenide material is a promising approach to increase the yield of high-quality radiation detectors as compared to cadmium zinc telluride. This paper reports a path to the advancement of the quaternary material to achieve the best detector performance. This advance may resolve the longstanding issues associated with cadmium zinc telluride-based X- and gamma-ray detectors.
    [Show full text]
  • A Dissertation Entitled Development of Back Contacts for Cdte Thin Films Solar Cells by Fadhil Khalaf Dahash Alfadhili Submit
    A Dissertation entitled Development of Back Contacts for CdTe Thin Films Solar Cells by Fadhil Khalaf Dahash Alfadhili Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Physics Dr. Michael J. Heben, Committee Chair Dr. Randy J. Ellingson, Committee Member ___________________________________________ Dr. Robert Collins, Committee Member Dr. Nikolas Podraza, Committee Member Dr. Daniel Georgiev, Committee Member ___________________________________________ Dr. Amanda C. Bryant-Friedrich, Dean College of Graduate Studies The University of Toledo May 2020 Copyright 2020 Fadhil Khalaf Dahash Alfadhili This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of Development of Back Contacts for CdTe Thin Films Solar Cells by Fadhil Khalaf Dahash Alfadhili Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Physics The University of Toledo May 2020 Thin film solar cells based on polycrystalline p-type cadmium telluride (CdTe) represent one of these the most promising photovoltaic (PV) device due to high efficiency and low-cost production. Currently, CdTe solar cells provide the lowest cost electricity generation in utility-scale applications, which is a cost-competitive with the traditional power source, fossil fuel. CdTe thin film PV has attained 22.1 % of power conversion efficiency for small area scale and 18.6 % for modules scale. However, the high efficiency of CdTe devices has been achieved by increasing the photo-generated current by changing the traditional window layer (CdS) of CdTe to a wider bandgap material with better band alignment.
    [Show full text]
  • Evaluation of a Small Cadmium Zinc Telluride Detector for Scintimammography
    Evaluation of a Small Cadmium Zinc Telluride Detector for Scintimammography Bryon Mueller, PhD1; Michael K. O’Connor, PhD1; Ira Blevis, PhD2; Deborah J. Rhodes, MD3; Robin Smith, MD3; Douglas A. Collins, MD1; and Stephen W. Phillips, MD1 1Department of Radiology, Mayo Clinic, Rochester, Minnesota; 2Functional Imaging, General Electric Medical Systems, Haifa, Israel; and 3Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota quently, the breast must be imaged in the prone lateral The purpose of this study was to evaluate a small semiconduc- position with poor visualization of lesions located in the tor-based gamma camera that may have applications in scinti- medial wall or close to the chest wall. Optimal scintimam- mammography. Methods: A small cadmium zinc telluride (CZT) mographic imaging requires a system that cannot only be ϫ detector was evaluated. The detector had a field of view of 20 positioned close to the breast but also allows the breast to be 20 cm with detector elements of 2.5 ϫ 2.5 mm in size. Both short-bore (35 mm) and long-bore (50 mm) collimators, imaging from any side with minimal interference from matched to the geometry of the detector elements, were eval- adjacent activity in the body. Conventional Anger-based uated. The imaging performance of the CZT detector was com- gamma cameras cannot be positioned in this manner be- pared with that of a conventional gamma camera equipped with cause of the 8- to 10-cm dead space between the active area all-purpose and ultra-high-resolution collimators. The perfor- and the physical edge of the detector.
    [Show full text]
  • Cadmium Zinc Telluride Detectors for a Next-Generation Hard X-Ray Telescope
    ©2021. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ Cadmium Zinc Telluride Detectors for a Next-Generation Hard X-ray Telescope J. Tanga,∗, F. Kislatb, H. Krawczynskia aWashington University in St. Louis, Physics Department, 1 Brookings Dr., CB 1105, St. Louis, MO 63130 bUniversity of New Hampshire, Department of Physics & Astronomy and Space Science Center, 8 College Rd, Durham, NH 03824 Abstract We are currently developing Cadmium Zinc Telluride (CZT) detectors for a next-generation space-borne hard X-ray telescope which can follow up on the highly successful NuSTAR (Nuclear Spectroscopic Telescope Array) mission. Since the launch of NuSTAR in 2012, there have been major advances in the area of X-ray mirrors, and state-of-the-art X-ray mirrors can improve on NuSTAR’s angular resolution of ∼1 arcmin Half Power Diameter (HPD) to 1500 or even 500 HPD. Consequently, the size of the detector pixels must be reduced to match this resolution. This paper presents detailed simulations of relatively thin (1 mm thick) CZT detectors with hexagonal pixels at a next-neighbor distance of 150 µm. The simulations account for the non-negligible spatial extent of the deposition of the energy of the incident photon, and include detailed modeling of the spreading of the free charge carriers as they move toward the detector electrodes. We discuss methods to reconstruct the energies of the incident photons, and the locations where the photons hit the detector. We show that the charge recorded in the brightest pixel and six adjacent pixels suffices to obtain excellent energy and spatial resolutions.
    [Show full text]