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Title: Research on CdZnTe and Other Novel Room Temperature Gamma Ray Spectrometer Materials

Abstract

Room temperature gamma-ray spectrometers are being developed for a number of years for national security applications where high sensitivity, low operating power and compactness are indispensable. The technology has matured now to the point where large volume (several cubic centimeters) and high energy resolution (approximately 1% at 660 eV) of gamma photons, are becoming available for their incorporation into portable systems for remote sensing of signatures from nuclear materials.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Fisk University
Sponsoring Org.:
USDOE
OSTI Identifier:
908231
Report Number(s):
DOE/ID/14555
TRN: US200722%%564
DOE Contract Number:
FG07-04ID14555
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE; ENERGY RESOLUTION; NATIONAL SECURITY; PHOTONS; REMOTE SENSING; SENSITIVITY; SPECTROMETERS; GAMMA RADIATION

Citation Formats

Arnold Burger, Michael gGoza, Yunlong Cui, Utpal N. Roy, and M. Guo. Research on CdZnTe and Other Novel Room Temperature Gamma Ray Spectrometer Materials. United States: N. p., 2007. Web. doi:10.2172/908231.
Arnold Burger, Michael gGoza, Yunlong Cui, Utpal N. Roy, & M. Guo. Research on CdZnTe and Other Novel Room Temperature Gamma Ray Spectrometer Materials. United States. doi:10.2172/908231.
Arnold Burger, Michael gGoza, Yunlong Cui, Utpal N. Roy, and M. Guo. Sat . "Research on CdZnTe and Other Novel Room Temperature Gamma Ray Spectrometer Materials". United States. doi:10.2172/908231. https://www.osti.gov/servlets/purl/908231.
@article{osti_908231,
title = {Research on CdZnTe and Other Novel Room Temperature Gamma Ray Spectrometer Materials},
author = {Arnold Burger and Michael gGoza and Yunlong Cui and Utpal N. Roy and M. Guo},
abstractNote = {Room temperature gamma-ray spectrometers are being developed for a number of years for national security applications where high sensitivity, low operating power and compactness are indispensable. The technology has matured now to the point where large volume (several cubic centimeters) and high energy resolution (approximately 1% at 660 eV) of gamma photons, are becoming available for their incorporation into portable systems for remote sensing of signatures from nuclear materials.},
doi = {10.2172/908231},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat May 05 00:00:00 EDT 2007},
month = {Sat May 05 00:00:00 EDT 2007}
}

Technical Report:

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  • The primary goal of this project has been to characterize and identify point defects (e.g., impurities, vacancies, vacancy-impurity complexes, etc.) in CdZnTe and determine the mechanisms by which these defects influence the carrier {mu}{tau}products. Special attention is given to the role of shallow donors, shallow acceptors, and deeper acceptors. There are two experimental focus areas in the project: (1) liquid-helium photoluminescence (PL) and PL excitation spectroscopy are used to identify and characterize donors and acceptors and to determine zinc molar fraction; and (2) electron paramagnetic resonance (EPR) and photoinduced EPR experiments are performed at liquid-helium temperature to identify paramagnetic pointmore » defects and to determine the concentration of these defects. Results from the two experimental focus areas are correlated with detector performance parameters (e.g., electron and hole {mu}{tau} products), crystal growth conditions, and microstructure analyses.« less
  • High-energy photon detectors have been constructed by engineering and fabricating p-i-n diode struitures consisting of bulk CdZnTe and epitaxial HgCdTe. The p-i-n structure was obtained by liquid-phase epitaxial growth of p and n doped HgCdTe layers on ``intrinsic`` CdZnTe material about 1 mm thick and approximately 25mm square. Curve tracing shows I-V curves with diode characteristics having resistivity above 10{sup 11} {Omega}-cm and leakage current of <400 pA to about {minus}60V reverse bias on a typical test piece approximately 5 {times} 8 {times} 1 mm. Spectra of similar test pieces have been obtained at room temperature with various nuclear isotopicmore » sources over the range of 22 keV to 662 keV which show exceptionally high energy resolution. Resolution as low as 1.82% FWHM was obtained for the 355 key line of {sup 133}Ba line with a P/V=3.4. The performance of these detectors combined with contemporary technology capable of fabricating megapixel 2D arrays of these II-VI materials open up manifold exciting applications in astrophysics, medical, industrial, environmental, and defense spectroscopy and imaging.« less
  • A significant amount of progress has been achieved in the development of the novel vacuum distillation method described in the proposal. The process for the purification of Te was fully developed and characterized in a series of trials. The purification effect was confirmed with GDMS sample analysis and indicates the process yields very high purity Te metal. Results of this initial process study have been submitted for publication in the Proceedings of the SPIE and will be presented on August 28, 2007 at the SPIE Optics and Photonics 2007 conference in San Diego, CA. Concurrent to the development of themore » Te process, processes for the purification of Cd, Zn, and Mn have also progressed. The development of the processes for Cd and Zn are nearly complete, while the development of the process for Mn is still in its infancy. It is expected that a full characterization of the Cd process will be completed within the next quarter, followed by Zn. Parallel to those characterization studies, efforts will be made to further develop the Mn purification process. Zone melting work for Te and Cd has also been efforted as per the project work schedule. Initial trials have been completed and the processes developed. Characterization of the results will be completed within the first fiscal year. Finally, an apparatus for the zone refinement of Cd, Zn, and Mn has been constructed and initial trials are set to begin shortly.« less
  • In this study, we report on the results of the investigation of lead iodide material properties. The effectiveness of zone refining purification methods on the material purity is determined by ICP-MS and ICP-OES and correlated to the electrical and physical material properties. We show that this zone refining method is very efficient in removing impurities from lead iodide and we also determine the segregation coefficient for some of these impurities. Triple axis x- ray diffraction (TAD) analysis has been used to determine the crystalline perfection of the lead iodide after applying various cutting, etching, and fabrication methods. The soft leadmore » iodide crystal was found to be damaged when cleaved by a razor blade, but by using a diamond wheel saw, followed by etching, the crystallinity of the material was improved, as observed by TAD. Low temperature photoluminescence also indicates an improvement in the material properties of the purified lead iodide. Electrical properties of lead iodide such as carrier mobility, were calculated based on carrier- phonon scattering. The results for the electrical properties were in good agreement with the experimental data.« less