Characterization of Extended Defects Observed in Cadmium Zinc Telluride (CZT) Crystal

2015 ◽  
Vol 1792 ◽  
Author(s):  
Samuel Uba ◽  
Stephen Babalola ◽  
Anwar Hossain ◽  
Ralph James
Keyword(s):  
Electrical Properties ◽  
Grain Boundaries ◽  
Cadmium Zinc Telluride ◽  
Zinc Telluride ◽  
High Energy ◽  
Extended Defects ◽  
Detector Performance ◽  
Te Inclusions ◽  
Czt Detectors ◽  
Cadmium Zinc

ABSTRACTCadmium Zinc Telluride (CZT) semiconductor crystal properties have been studied extensively with a focus on correlations to their radiation detector performance. The need for defect-free CZT crystal is imperative for optimal detector performance. Extended defects like Tellurium (Te) inclusions, twins, sub-grain boundaries, and dislocations are common defects found in CZT crystals; they alter the electrical properties and, therefore, the crystal's response to high energy radiation. In this research we studied the extended defects in CZT crystals from two separate ingots grown using the low-pressure Bridgman technique. We fabricated several detectors cut from wafers of two separate ingots by dicing, lapping, polishing, etching and applying gold metal contacts on the main surfaces of the crystals. Using infrared (IR) transmission microscope we analyzed the defects observed in the CZT detectors, showing three dimensional scans and plot size distributions of Te inclusions, twins and sub-grain boundaries observed in particular regions of the CZT detectors. We characterized electrical properties of the detectors by measuring bulk resistivity and detector response to gamma radiation. We observed that CZT detectors with more extended defects showed poor opto-electrical properties compared to detectors with fewer defects.

scholarly journals Advances in CdZnTeSe for Radiation Detector Applications

Radiation ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 123-130
Author(s):  
Utpal N. Roy ◽  
Giuseppe S. Camarda ◽  
Yonggang Cui ◽  
Ralph B. James
Keyword(s):  
Grain Boundary ◽  
Cadmium Zinc Telluride ◽  
Radiation Detector ◽  
Zinc Telluride ◽  
High Energy ◽  
Detector Performance ◽  
Wide Range ◽  
Temperature Detector ◽  
Te Inclusions ◽  
Cadmium Zinc

Detection of X- and gamma-rays is essential to a wide range of applications from medical imaging to high energy physics, astronomy, and homeland security. Cadmium zinc telluride (CZT) is the most widely used material for room-temperature detector applications and has been fulfilling the requirements for growing detection demands over the last three decades. However, CZT still suffers from the presence of a high density of performance-limiting defects, such as sub-grain boundary networks and Te inclusions. Cadmium zinc telluride selenide (CZTS) is an emerging material with compelling properties that mitigate some of the long-standing issues seen in CZT. This new quaternary is free from sub-grain boundary networks and possesses very few Te inclusions. In addition, the material offers a high degree of compositional homogeneity. The advancement of CZTS has accelerated through investigations of the material properties and virtual Frisch-grid (VFG) detector performance. The excellent material quality with highly reduced performance-limiting defects elevates the importance of CZTS as a potential replacement to CZT at a substantially lower cost.

scholarly journals Impact of selenium addition to the cadmium-zinc-telluride matrix for producing high energy resolution X-and gamma-ray detectors

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Utpal N. Roy ◽  
Giuseppe S. Camarda ◽  
Yonggang Cui ◽  
Ge Yang ◽  
Ralph B. James
Keyword(s):  
Grain Boundaries ◽  
Energy Resolution ◽  
Room Temperature ◽  
Cadmium Zinc Telluride ◽  
Zinc Telluride ◽  
High Energy ◽  
High Energy Resolution ◽  
Material Quality ◽  
X Ray ◽  
Cadmium Zinc

AbstractBoth material quality and detector performance have been steadily improving over the past few years for the leading room temperature radiation detector material cadmium-zinc-telluride (CdZnTe). However, although tremendous progress being made, CdZnTe still suffers from high concentrations of performance-limiting defects, such as Te inclusions, networks of sub-grain boundaries and compositional inhomogeneity due to the higher segregation coefficient of Zn. Adding as low as 2% (atomic) Se into CdZnTe matrix was found to successfully mitigate many performance-limiting defects and provide improved compositional homogeneity. Here we report record-high performance of Virtual Frisch Grid (VFG) detector fabricated from as-grown Cd0.9Zn0.1Te0.98Se0.02 ingot grown by the Traveling Heater Method (THM). Benefiting from superior material quality, we achieved superb energy resolution of 0.77% at 662 keV (as-measured without charge-loss correction algorithms) registered at room temperature. The absence of residual thermal stress in the detector was revealed from white beam X-ray topographic images, which was also confirmed by Infra-Red (IR) transmission imaging under cross polarizers. Furthermore, neither sub-grain boundaries nor their networks were observed from the X-ray topographic image. However, large concentrations of extrinsic impurities were revealed in as-grown materials, suggesting a high likelihood for further reduction in the energy resolution after improved purification of the starting material.

On the Active Volume of Cadmium Zinc Telluride Gamma-Ray Spectrometers

1997 ◽  
Vol 487 ◽  
Author(s):  
J. C. Lund ◽  
B. A. Brunett ◽  
T. P. Viles ◽  
N. R. Hilton ◽  
R. B. James
Keyword(s):  
Gamma Ray ◽  
Cadmium Zinc Telluride ◽  
Pulse Height ◽  
Zinc Telluride ◽  
Charge Trapping ◽  
Active Volume ◽  
Electronic Signal Processing ◽  
Czt Detectors ◽  
Unipolar Devices ◽  
Cadmium Zinc

AbstractIn this paper we develop quantitative models to predict the active volume of cadmium zinc telluride (CZT) detectors operated as gamma-ray pulse height spectrometers. Three cases are considered: a conventional planar detector, a unipolar device, and a detector in which electronic signal processing has been applied to correct for charge trapping effects. We find that existing detectors are very limited in their maximum attainable active volume, but unipolar devices with charge correction show promise for producing large active volume devices.

Thermal Annealing: A Technique to Improve the Performance of Cadmium Zinc Telluride (CZT) Material for Semiconductor Radiation Detector Applications

2012 ◽  
Author(s):  
Aaron L. Adams ◽  
Aschalew Kassu ◽  
Wing Chan ◽  
Mebougna Drabo ◽  
Rodney Pinder ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Thermal Annealing ◽  
Large Volume ◽  
Cadmium Zinc Telluride ◽  
Radiation Detector ◽  
Zinc Telluride ◽  
Radiation Detectors ◽  
Nuclear Radiation ◽  
Structural Defects ◽  
Cadmium Zinc

Extensive research was undertaken over the past 20 years to investigate the suitability of cadmium zinc telluride (CZT) crystals as a material for room-temperature nuclear-radiation detectors. Large-volume CZT crystals, with thicknesses up to 2 cm and large effective areas of roughly 5–10 cm2, are needed to fabricate efficient detectors that meet the working requirements of federal agencies, such as the DOE/NNSA (Department Energy National Nuclear Security Administration), Department of Homeland Security (DHS), and the Department of Defense (DOD). However, because of the imperfect methods for growing crystals, the resulting large-volume crystals most often are not perfect single ones, and contain structural defects such as voids, pipes, impurities from source materials, tellurium inclusions and precipitates, vacancies, and vacancy-impurity complexes generated during the process of their production. Other extended defects that may be present include grain boundaries, micro twins, and walls of dislocations (sub-grain boundaries). Identifying these defects, controlling their occurrence and eliminating them from the bulk CZT material currently are important tasks that will improve the yield of detector-grade crystals from ingots, and ultimately better their performance. In this study, we used a post-growth thermal annealing technique to remove the performance-limiting defects caused by tellurium inclusions and associated impurities in the CZT crystals. We realized a 66% ± 16% reduction in the size of the inclusions, with an overall elimination of 17% ± 2% of them. We believe that our experimental results offer a better understanding of the optimal annealing parameters, and of the dynamic properties of post-growth annealing processes.

scholarly journals Modern possibilities of cardiovascular imaging using gamma cameras with cadmium–zinc–telluride-detectors

2020 ◽  
Vol 24 (3) ◽  
pp. 11
Author(s):  
S. M. Minin ◽  
K. V. Zavadovky ◽  
N. A. Nikitin ◽  
A. V. Mochula ◽  
A. B. Romanov
Keyword(s):  
Conflict Of Interest ◽  
Cadmium Zinc Telluride ◽  
Zinc Telluride ◽  
Diagnostic Tools ◽  
Cardiac Spect ◽  
Gamma Cameras ◽  
Non Invasive ◽  
Flow Reserve ◽  
Czt Detectors ◽  
Cadmium Zinc

<p>Myocardial perfusion imaging is considered one of the leading non-invasive diagnostic tools for the assessment of patients with known or suspected coronary artery disease and other cardiac pathologies. The technical improvement of the currently used gamma-tomographic devices has increased the diagnostic capability of this technique. In recent years, the use of dedicated cardiac SPECT cameras with solid-state cadmium–zinc–telluride (CZT) technology has increased in nuclear imaging. These new CZT technologies have several advantages over existing scanner models. The development of new CZT detectors and their collimator configuration has increased scanning sensitivity and spatial resolution values. Also, due to the significantly higher sensitivity of new CZT detectors and new methods of data processing, radiologists have already introduced new scanning protocols and methods for radionuclide assessment of myocardial blood flow, reserve and non-invasive visualisation of the functioning of the sympathetic nervous system into clinical practice. The purpose of this review is to provide data on the main technical characteristics of gamma cameras equipped CZT detectors as well as the current possibilities of using CZT cameras for examining patients with various cardiovascular diseases.</p><p>Received 1 April 2020. Revised 22 April 2020. Accepted 30 April 2019.</p><p><strong>Funding:</strong> The work is supported by a grant of the Russian Science Foundation No. 17-75-20118.</p><p><strong>Conflict of interest:</strong> Authors declare no conflict of interest.</p><p><strong>Author contributions</strong><br />Conception and study design: S.M. Minin, K.V. Zavadovky, A.B. Romanov<br />Drafting the article: S.M. Minin, K.V. Zavadovky, N.A. Nikitin, A.V. Mochula, A.B. Romanov<br />Critical revision of the article: S.M. Minin, K.V. Zavadovky<br />Final approval of the version to be published: S.M. Minin, K.V. Zavadovky, N.A. Nikitin, A.V. Mochula, A.B. Romanov</p>

scholarly journals Opto-electrical characterization and X-ray Mapping of large-volume cadmium zinc telluride radiation detectors

2009 ◽  
Vol 1164 ◽  
Author(s):  
Ge Yang ◽  
Aleksey E Bolotnik ◽  
Giuseppe Camarda ◽  
Yonggang Cui ◽  
Anwar Hossain ◽  
...  
Keyword(s):  
Large Volume ◽  
Cadmium Zinc Telluride ◽  
Radiation Detection ◽  
Zinc Telluride ◽  
Radiation Detectors ◽  
Internal Electric Field ◽  
Pockels Effect ◽  
X Ray ◽  
Czt Detectors ◽  
Cadmium Zinc

AbstractLarge-volume cadmium zinc telluride (CZT) radiation detectors would greatly improve radiation detection capabilities and, therefore, attract extensive scientific and commercial interests. CZT crystals with volumes as large as hundreds of centimeters can be achieved today due to improvements in the crystal growth technology. However, the poor performance of large-volume CZT detectors is still a challenging problem affecting the commercialization of CZT detectors and imaging arrays. We have employed Pockels effect measurements and synchrotron X-ray mapping techniques to investigate the performance-limiting factors for large-volume CZT detectors. Experimental results with the above characterization methods reveal the non-uniform distribution of internal electric field of large-volume CZT detectors, which help us to better understand the responsible mechanism for the insufficient carrier collection in large-volume CZT detectors.

Detector performance crystallinity and impurity study of cadmium zinc telluride crystals grown from the melt

2001 ◽  
Author(s):  
Haim Hermon ◽  
Michael M. Schieber ◽  
M. Factor ◽  
Tuviah E. Schlesinger ◽  
Ralph B. James ◽  
...  
Keyword(s):  
Cadmium Zinc Telluride ◽  
Zinc Telluride ◽  
Detector Performance ◽  
Cadmium Zinc

Mapping of Large Area Cadmium Zinc Telluride (CZT) Wafers: Apparatus and Methods

1997 ◽  
Vol 487 ◽  
Author(s):  
B. A. Brunett ◽  
J. M. Van Scyoc ◽  
H. Yoon ◽  
T. S. Gilbert ◽  
T. E. Schlesinger ◽  
...  
Keyword(s):  
Transport Properties ◽  
Cadmium Zinc Telluride ◽  
Radiation Detector ◽  
Zinc Telluride ◽  
Hole Transport ◽  
Device Fabrication ◽  
Great Promise ◽  
Large Area ◽  
Detector Performance ◽  
Cadmium Zinc

AbstractCadmium Zinc Telluride (CZT) shows great promise as a semiconductor radiation detector material. CZT possesses advantageous material properties over other radiation detector materials in use today, such as a high intrinsic resistivity and a high cross-section for x and γ-rays. However, presently available CZT is not without limitations. The hole transport properties severely limit the performance of these detectors, and the yield of material possessing adequate electron transport properties is currently much lower than desired. The result of these material deficiencies is a lack of inexpensive CZT crystals of large volume for several radiation detector applications. One approach to help alleviate this problem is to measure the spatial distribution (or map) the electrical properties of large area CZT wafers prior to device fabrication. This mapping can accomplish two goals: identify regions of the wafers suitable for detector fabrication and correlate the distribution of crystalline defects with the detector performance. The results of this characterization can then be used by the crystal manufacturers to optimize their growth processes. In this work, we discuss the design and performance of apparatus for measuring the electrical characteristics of entire CZT wafers (up to 10 cm × 10 cm). The data acquisition and manipulation will be discussed and some typical data will be presented.

Study of impurity segregation, crystallinity, and detector performance of melt-grown cadmium zinc telluride crystals

2002 ◽  
Vol 237-239 ◽  
pp. 2082-2090 ◽  
Author(s):  
M. Schieber ◽  
T.E. Schlesinger ◽  
R.B. James ◽  
H. Hermon ◽  
H. Yoon ◽  
...  
Keyword(s):  
Cadmium Zinc Telluride ◽  
Zinc Telluride ◽  
Detector Performance ◽  
Impurity Segregation ◽  
Cadmium Zinc
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