Properties Of Radiation Detectors Research Articles

A novel material for radiation detection application of zinc bismuth lithium borotellurite glass doped with Dy2O3

Radiation detection glass with the following chemical composition B2O3–TeO2–Li2O3–Bi2O3–ZnO doped with Dy2O3 where x = 0.00, 0.10, 0.50, 1.00, 1.50 and 2.00 mol%, was developed for the characterization of physical properties such as density, molar volume (Vm), and refractive index, optical absorption, luminescence, CIE's diagram, and radiation detection properties. The density and refractive index of glass samples increase with the increase of Dy2O3 composition. The optical property of glass shows eight strongest peaks from 6H15/2 centering at 263 nm (4I13/2 + 4F7/2), 298 nm (4G11/2), 357 nm (4I15/2), 803 nm (6F5/2), 897 nm (6F7/2), 1090 nm (6H7/2 + 6F9/2), 1272 nm (6F11/2 + 6H9/2) and 1671 nm (6H11/2), respectively. The emission peaks are r (4F9/2), 481 nm (6H15/2), 575 nm (6H13/2), 664 nm (6H11/2), and 751 nm (6H9/2) under excited at 453 nm (4F9/2), respectively. The excitation peaks under emission at 575 nm from 6H15/2 centering at 350 nm (6P7/2), 365 nm (4P3/2), 388 nm (4K17/2), 425 nm (4G11/2), 453 nm (4I15/2), and 471 nm (4F9/2) respectively. The study of luminescence characteristics, which includes emission, excitation, and CIE diagrams, reveals white emission bands that coincide with the CIE diagram. Furthermore, measuring the parameters of the thermoluminescence dosimeter (TLD) recorded with a heating rate of 5 °C/s in the temperature up to a maximum of 400 °C yields good results in low dose radiation detection. Based on all the results, it was determined that this glass can be a candidate for radiation detection materials in the future.

Charge transport comparison of FA, MA and Cs lead halide perovskite single crystals for radiation detection

We report a systematic comparison of the charge transport and radiation detection properties of inorganic and organic metal bromide single crystal perovskites. We studied the performance of Bridgman-grown CsPbBr3 single crystals, together with solution-grown FAPbBr3 and MAPbBr3 single crystals. Laser time of flight is used to measure the drift mobilities for all samples, and we report a maxium mobility value of 121 ± 10 cm V−1 s−1 for CsPbBr3. Alpha particle measurements were used to assess the mobility-lifetime products, with values recorded in the range of 2 × 10−4 cm2 V−1 to 1 × 10−3 cm2 V−1. Low temperature measurements showed an increase in bulk resistivity at temperatures down to 260 K, but no significant change to the drift mobilities. The overall performance of the Cs, FA and MA samples is compared and their potential for use in gamma spectroscopy measurements is discussed.

Influence of carrier trapping on radiation detection properties in CVD grown 4H-SiC epitaxial layers with varying thickness up to 250 µm

Low doped n-type 4H-SiC epitaxial layers of thickness 50, 150, and 250 µm grown by hot wall chemical vapor deposition were used to fabricate Ni/4H-SiC Schottky radiation detectors. The epitaxial layers were grown on the (0001) face of highly conductive bulk 4H-SiC substrates 8° offcut towards the 〈112¯0〉 direction. The 50, 150, and 250 µm thick epilayer detectors, under optimized settings, showed energy resolutions of 2.0%, 0.78%, and 0.63%, respectively for 5.48 MeV alpha particles. Deep level transient spectroscopy studies showed that the observed variation in the detector resolution is linked to the defect parameters in the devices. Least-squares fitting of the bias dependence of the charge collection efficiency according to a drift-diffusion model, revealed minority carrier diffusion lengths of 16, 10, and 9.2 µm, respectively, implying that the detectors are not limited by minority carrier trapping. The detector performance was observed to be primarily dependent on the concentration and capture cross-sections of the lifetime killing electron traps Z1/2 and EH6/7.

Improvement in Plastic Scintillator with Loading of BaFBr:Eu²⁺ Radioluminescence Phosphor

This article describes a new concept of developing a composite plastic scintillator (PS) with better light out and detection efficiency of ionizing radiations by loading high Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> radioluminescence (RL) phosphor powder. Gamma-ray interaction in PSs has been enhanced due to increased photoelectric absorption in the loaded BaFBr:Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> phosphor powder. RL BaFBr:Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> powder has been synthesized by a high-temperature solid-state diffusion method in reducing atmosphere. Polystyrene-based PS sheets of 250±50 μm thickness have been prepared with 2.5-diphenyl oxazole (PPO) and 1.4-bis(5-phenyl-2-oxazolyl) benzene (POPOP) as primary and secondary fluors, respectively, mixed with the synthesized phosphor powder in different weight percentages. Radiation detection properties of the composite PS have been studied for alpha, beta, neutron, and gamma radiations of different energies. The composite PS sheet loaded with 20 wt% of phosphor powder showed maximum intensity for RL and photoluminescence (PL). Studies also confirmed a significant increase in the radiation detection efficiency in composite PS for various energies of beta and gamma rays. The lifetime measurement of the composite PS showed same nanosecond lifetime which is appropriate for fast counting and matches closely with the PS without loading. Pulse height analysis for various ionizing radiations of different energies confirmed significant improvement in the detection efficiency of loaded PSs.

Correlation of Space Charge Limited Current and γ-Ray Response of CdxZn1-xTe1-ySey Room-Temperature Radiation Detectors

In this letter we report a direct correlation between the space charge limited current flow and radiation detection properties of Cd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-y</sub> Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> (CZTS) detector. CZTS is a recently discovered quaternary wide bandgap semiconductor for room-temperature gamma photon detection. The CZTS single crystals have been grown in-house using a modified Bridgman technique. Planar detectors were fabricated and characterized in terms of charge carrier flow and radiation detection measurements. An anomalous current flow falling outside the Lampert's triangle in logJ - logV plot, has been observed which is not generally seen in semiconductor detectors governed by space-charge limited current flow mechanism. The anomalous behavior has been attributed to the presence of electron traps. The devices were tested for their radiation detection properties by acquiring pulse height spectra using <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">241</sup> Am and a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs isotopes as a source of alpha particles and gamma photons, respectively. It was further noticed that the only detectors which worked satisfactorily as radiation detectors, did not exhibit the anomalous current flow mechanism.

Growth of Large-Area Cd₀.₉Zn₀.₁Te Single Crystals and Fabrication of Pixelated Guard-Ring Detector for Room-Temperature γ-Ray Detection

Large-volume detector-grade Cd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.9</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> Te (CZT) single crystals were grown using a vertical Bridgman technique. The bulk resistivity of the as-grown crystal was found to be ~5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> Q-cm from current-voltage measurements. A 19.0 × 19.0 × 5.0 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> block of the crystal was used to fabricate a detector with 10 × 10 pixelated anode configuration integrated with interpixel guard rings. The detector was tested for its radiation detection properties using 662-keV gamma rays from a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs source. The pixels exhibited well-resolved gamma pulse-height spectra (PHS) with percentage energy resolution ~1.6% at 662 keV. A few pixels exhibited tailing of the photopeak on the lower energy side indicating the presence of hole traps. Biparametric plots (BPs) were obtained from digitally recorded preamplifier pulses. The BPs showed anomalous behavior, which was correlated with the gamma interactions in the active region of the detector in virtual Frisch grid configuration. The BPs also enabled to extract PHS free from the extensive tailing of the photopeak.

Bismuth chalcohalide-based nanocomposite for application in ionising radiation detectors

Bismuth sulpho iodide (BiSI) belongs to the family of chalcohalides, which present several attractive electro-optic properties. In particular, BiSI is a semiconductor which could be used in X and gamma ray detection due to a band gap of 1.6 eV, density of 6.4 g cm−3, and absorption coefficient for 60 keV radiation of 5.6 cm2 g−1. This work presents a facile synthesis under solvothermal conditions of a nanocomposite consisting of BiSI nanorods and amorphous carbon structures. Furthermore, it studies its ionising radiation detection properties at room temperature, when prototype detectors were built from pellets. The construction conditions of pellets were also studied, varying the applied pressure and heat treatment to the nanocomposite. Dark current density and response to different exposure rates of a 241Am source were measured for the prototype detectors built. It was found that heat treatment of pellets considerably improves detectors performance. Dark current density was one order of magnitude lower than for the pellets without heat treatment, and its response to the 241Am source, linear, with a signal to noise ratio of 7 for 20 V. Finally, the resistivity for the heat treated detector was in the order of 1011 Ω cm, comparable to other materials studied for this application.

Advances in High-Resolution Radiation Detection Using 4H-SiC Epitaxial Layer Devices.

Advances towards achieving the goal of miniature 4H-SiC based radiation detectors for harsh environment application have been studied extensively and reviewed in this article. The miniaturized devices were developed at the University of South Carolina (UofSC) on 8 × 8 mm 4H-SiC epitaxial layer wafers with an active area of ≈11 mm2. The thicknesses of the actual epitaxial layers were either 20 or 50 µm. The article reviews the investigation of defect levels in 4H-SiC epilayers and radiation detection properties of Schottky barrier devices (SBDs) fabricated in our laboratories at UofSC. Our studies led to the development of miniature SBDs with superior quality radiation detectors with highest reported energy resolution for alpha particles. The primary findings of this article shed light on defect identification in 4H-SiC epilayers and their correlation with the radiation detection properties.

Methylammonium lead tribromide semiconductors: Ionizing radiation detection and electronic properties

Abstract The response of single crystal methylammonium lead tribromide (MAPbBr 3 or MAPB) semiconductors to alpha particles at low voltage is presented. Through analysis of the preamplifier traces induced by 210Po alpha particles and collecting holes, we were able to determine the mobility–lifetime product, apparent mobility, trapping time constant, and the detrapping time constant. In addition, a quantitative study of the rate of positive polarization and device breakdown time at different applied voltages is presented. Finally, using a 239 Pu/Be fast neutron source, we were able to demonstrate the response of MAPB to fast neutrons for the first time via benchmarking experiment with Monte Carlo simulations.

Stable room-temperature thallium bromide semiconductor radiation detectors

Thallium bromide (TlBr) is a highly efficient ionic semiconductor with excellent radiation detection properties. However, at room temperature, TlBr devices polarize under an applied electric field. This phenomenon not only degrades the charge collection efficiency of the detectors but also promotes chemical reaction of the metal electrodes with bromine, resulting in an unstable electric field and premature failure of the device. This drawback has been crippling the TlBr semiconductor radiation detector technology over the past few decades. In this exhaustive study, this polarization phenomenon has been counteracted using innovative bias polarity switching schemes. Here the highly mobile Br− species, with an estimated electro-diffusion velocity of 10−8 cm/s, face opposing electro-migration forces during every polarity switch. This minimizes the device polarization and availability of Br− ions near the metal electrode. Our results indicate that it is possible to achieve longer device lifetimes spanning more than 17 000 h (five years of 8 × 7 operation) for planar and pixelated radiation detectors using this technique. On the other hand, at constant bias, 2500 h is the longest reported lifetime with most devices less than 1000 h. After testing several biasing switching schemes, it is concluded that the critical bias switching frequency at an applied bias of 1000 V/cm is about 17 μHz. Using this groundbreaking result, it will now be possible to deploy this highly efficient room temperature semiconductor material for field applications in homeland security, medical imaging, and physics research.

Taking Advantage of Disorder: Small-Molecule Organic Glasses for Radiation Detection and Particle Discrimination.

A series of fluorescent silyl-fluorene molecules were synthesized and studied with respect to their photophysical properties and response toward ionizing neutron and gamma-ray radiation. Optically transparent and stable organic glasses were prepared from these materials using a bulk melt-casting procedure. The prepared organic glass monoliths provided fluorescence quantum yields and radiation detection properties exceeding the highest-performing benchmark materials such as solution-grown trans-stilbene crystals. Co-melts based on blends of two different glass-forming compounds were prepared with the goal of enhancing the stability of the amorphous state. Accelerated aging experiments on co-melt mixtures ranging from 0% to 100% of each component indicated improved resistance to recrystallization in the glass blends, able to remain fully amorphous for >1 month at 60 °C. Secondary dopants comprising singlet fluorophores or iridium organometallic compounds provided further improved detection efficiency, as evaluated by light yield and neutron/gamma particle discrimination measurements. Optimized singlet and triplet doping levels were determined to be 0.05 wt % 1,4-bis(2-methylstyryl)benzene singlet fluorophore and 0.28 wt % Ir3+, respectively.

Investigation of radiation detection properties of CRY-018 and CRY-019 scintillators for medical imaging

During the last years the research for new scintillation crystals has been crucial for the improvement of imaging performance in nuclear medicine applications. Crytur company has recently released two new scintillators named CRY-018 and CRY-019 which are non hygroscopic, have short decay time and low refraction index. They represent the ideal candidates to substitute NaI:Tl and BGO crystals in future PET ad SPECT applications. The purpose of this work is to characterize this unknown crystals, look for possible applications in imaging for nuclear medicine. The results of this work were compared with the results obtained with a LaBr3:ce scintillation crystal. This particular crystal is used as a comparison benchmark because of its strong linear pulse height uniformity response and high energy resolution. Measurements have been performed with a high count rate which is typical for medical applications. Irradiation of the crystals have been performed in three different geometries and in a photon energy range suitable with SPECT and PET applications. The experimental results identify the CRY-018 as an Yttrium and Silicon mixture and the CRY-019 with as Lutetium and Silicon one. Moreover a light yield of about 45% of LaBr3 one, was obtained for both the CRY-018 and CRY-019. This is one of the higher light yield between most of the scintillation crystals usually used in nuclear medicine. Both crystals are characterized by a non-proportionality in the pulse height linearity response. Energy resolutions of 7.4% for CRY-018 and 8.4% for CRY-019 at 661 keV, have been measured. The intrinsic component of the energy resolution has been esteemed for all three scintillators. An intrinsic detection efficiency of about 45% at 122 keV for CRY-018 and 14% at 661 keV for CRY-019 has been measured. Compared with LaBr3:Ce efficiency, which is highly deteriorated by the coating required by the hygroscopicity, CRY-018 and CRY-019 are really interesting considering that these two samples are only 6 mm thick. Crytur's crystals seem to be suitable for nuclear medicine applications.

Molecular Dynamics Simulations of Dislocations in TlBr Crystals under an Electrical Field

ABSTRACTTlBr crystals have superior radiation detection properties; however, their properties degrade in the range of hours to weeks when an operating electrical field is applied. To account for this rapid degradation using the widely-accepted vacancy migration mechanism, the vacancy concentration must be orders of magnitude higher than any conventional estimates. The present work has incorporated a new analytical variable charge model in molecular dynamics (MD) simulations to examine the structural changes of materials under electrical fields. Our simulations indicate that dislocations in TlBr move under electrical fields. This discovery can lead to new understanding of TlBr aging mechanisms under external fields.

WE‐C‐TOUR‐I‐01: Dosimters for QC in Diagnostic Imaging

Tour Leader: Xia Jiang, Ohio State University, Columbus, OHTour Guides:Xia Jiang, Ohio State University, Columbus, OHKevin Little, The University of Chicago, Chicago, ILAdrien Sanchez, University of Chicago, Chicago, ILParticipating Vendors:IBAPTW ‐ New YorkRadcal CorporationRTI Electronics, Inc.Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year's Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introduction and background given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM‐member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions.Outline: Types and properties of radiation detectors and dosimeters Ionization chamber dosimeters Solid state dosimeters Dosimeter calibration: Primary and secondary standards dosimetry laboratories Instruments for measuring tube voltage and exposure timeVendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use. Learning Objectives: Understand the types and properties of different instrumentations used for quality control in diagnostic imaging. Understand the process of dosimeter calibration. Gain familiarity with the latest commercial dosimeter systems from different vendors.

TU‐E‐TOUR‐I‐00: Exhibit Hall Guided Tours‐Dosimters for QC in Diagnostic Imaging (Tuesday)

Tour Leader: Xia Jiang, Ohio State University, Columbus, OHTour Guides:Xia Jiang, Ohio State University, Columbus, OHKevin Little, The University of Chicago, Chicago, ILChristina Sammet, Lurie Children's Hospital of Chicago, Chicago, ILParticipating Vendors:IBAPTW ‐ New YorkRadcal CorporationRTI Electronics, Inc.Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year's Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introduction and background given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM‐member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions.Outline: Types and properties of radiation detectors and dosimeters Ionization chamber dosimeters Solid state dosimeters Dosimeter calibration: Primary and secondary standards dosimetry laboratories Instruments for measuring tube voltage and exposure timeVendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use. Learning Objectives: Understand the types and properties of different instrumentations used for quality control in diagnostic imaging. Understand the process of dosimeter calibration. Gain familiarity with the latest commercial dosimeter systems from different vendors.

TU‐E‐TOUR‐I‐01: Dosimters for QC in Diagnostic Imaging

Tour Leader: Xia Jiang, Ohio State University, Columbus, OHTour Guides:Xia Jiang, Ohio State University, Columbus, OHKevin Little, The University of Chicago, Chicago, ILChristina Sammet, Lurie Children's Hospital of Chicago, Chicago, ILParticipating Vendors:IBAPTW ‐ New YorkRadcal CorporationRTI Electronics, Inc.Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year's Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introduction and background given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM‐member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions.Outline: Types and properties of radiation detectors and dosimeters Ionization chamber dosimeters Solid state dosimeters Dosimeter calibration: Primary and secondary standards dosimetry laboratories Instruments for measuring tube voltage and exposure timeVendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use. Learning Objectives: Understand the types and properties of different instrumentations used for quality control in diagnostic imaging. Understand the process of dosimeter calibration. Gain familiarity with the latest commercial dosimeter systems from different vendors.

WE‐C‐TOUR‐I‐00: Exhibit Hall Guided Tours‐Dosimters for QC in Diagnostic Imaging (Wednesday)

Tour Leader: Xia Jiang, Ohio State University, Columbus, OHTour Guides:Xia Jiang, Ohio State University, Columbus, OHKevin Little, The University of Chicago, Chicago, ILAdrien Sanchez, University of Chicago, Chicago, ILParticipating Vendors:IBAPTW ‐ New YorkRadcal CorporationRTI Electronics, Inc.Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year's Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introduction and background given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM‐member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions.Outline: Types and properties of radiation detectors and dosimeters Ionization chamber dosimeters Solid state dosimeters Dosimeter calibration: Primary and secondary standards dosimetry laboratories Instruments for measuring tube voltage and exposure timeVendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use. Learning Objectives: Understand the types and properties of different instrumentations used for quality control in diagnostic imaging. Understand the process of dosimeter calibration. Gain familiarity with the latest commercial dosimeter systems from different vendors.

Study of radiation detection properties of GaN pn diode

Recently, GaN, which has remarkable properties as a material for optical devices and high-power electron devices, has also attracted attention as a material for radiation detectors. We previously suggested the use of BGaN as a neutron detector material. However, the radiation detection characteristics of GaN itself are not yet adequately understood. For realizing a BGaN neutron detector, the understanding of the radiation detection characteristics of GaN, which is a base material of the neutron detector, is important. In this study, we evaluated the radiation detection characteristics of GaN. We performed I–V and energy spectrum measurements under alpha ray, gamma ray, and thermal neutron irradiations to characterize the radiation detection characteristics of a GaN diode. The obtained results indicate that GaN is an effective material for our proposed new BGaN-based neutron detector.

The Influence of Thermal Treatment on Monocrystalline CZT and Tellurium Inclusions

ABSTRACTCadmium Zinc Telluride (CZT), considered as a viable material for use in room temperature radiation detectors, has an undesired presence of tellurium inclusions in the bulk. Thermal treatment, in the form of annealing, has been utilized to test the viability of refining CZT into better detector material, either by the elimination of the tellurium inclusions or by the migration of the inclusions under a temperature gradient, but usually with a deterioration of electrical properties. We took infrared micrographs and current voltage (IV) characteristics of CZT samples prior to thermal treatment. We carried out 24-hour thermal treatments with a range of temperature from 100°C to 700°C to determine an optimal annealing temperature and to verify changes in the sizes, morphologies, and locations of the tellurium inclusions on the surfaces and within the crystal bulk of the CZT. The IV curves and resistivities prior to and after thermal treatments were compared, as were the infrared micrographs before and after annealing. Also, the changes in electrical properties of the samples with annealing conditions were compared against structural changes monitored at the same steps during the annealing process, in order to understand the effects of the thermal annealing to the radiation detector properties of the material. Correlations between the shape, size and position of inclusions and electrical properties of the material were attempted.

Neutron detection using boron gallium nitride semiconductor material

In this study, we developed a new neutron-detection device using a boron gallium nitride (BGaN) semiconductor in which the B atom acts as a neutron converter. BGaN and gallium nitride (GaN) samples were grown by metal organic vapor phase epitaxy, and their radiation detection properties were evaluated. GaN exhibited good sensitivity to α-rays but poor sensitivity to γ-rays. Moreover, we confirmed that electrons were generated in the depletion layer under neutron irradiation. This resulted in a neutron-detection signal after α-rays were generated by the capture of neutrons by the B atoms. These results prove that BGaN is useful as a neutron-detecting semiconductor material.