Simulation, modeling, and crystal growth of Cd0.9Zn0.1Te for nuclear spectrometers |
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Authors: | Krishna C Mandal Sung Hoon Kang Michael Choi Job Bello Lili Zheng Hui Zhang Michael Groza Utpal N Roy Arnold Burger Gerald E Jellison David E Holcomb Gomez W Wright Joseph A Williams |
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Affiliation: | (1) EIC Laboratories, Inc., 111 Downey Street, 02062 Norwood, MA;(2) Department of Mechanical Engineering, State University of New York at Stony Brook, 11794 Stony Brook, NY;(3) Center of Excellence in Physics and Chemistry of Materials, Fisk University, 37208 Nashville, TN;(4) Oak Ridge National Laboratory, 37831 Oak Ridge, TN |
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Abstract: | High-quality, large (10 cm long and 2.5 cm diameter), nuclear spectrometer grade Cd0.9Zn0.1Te (CZT) single crystals have been grown by a controlled vertical Bridgman technique using in-house zone refined precursor
materials (Cd, Zn, and Te). A state-of-the-art computer model, multizone adaptive scheme for transport and phase-change processes
(MASTRAP), is used to model heat and mass transfer in the Bridgman growth system and to predict the stress distribution in
the as-grown CZT crystal and optimize the thermal profile. The model accounts for heat transfer in the multiphase system,
convection in the melt, and interface dynamics. The grown semi-insulating (SI) CZT crystals have demonstrated promising results
for high-resolution room-temperature radiation detectors due to their high dark resistivity (ρ≈2.8 × 1011 Θ cm), good charge-transport properties electron and hole mobility-life-time product, μτe≈(2–5)×10−3 and μτh≈(3–5)×10−5 respectively, and low cost of production. Spectroscopic ellipsometry and optical transmission measurements were carried out
on the grown CZT crystals using two-modulator generalized ellipsometry (2-MGE). The refractive index n and extinction coefficient
k were determined by mathematically eliminating the ∼3-nm surface roughness layer. Nuclear detection measurements on the single-element
CZT detectors with 241Am and 137Cs clearly detected 59.6 and 662 keV energies with energy resolution (FWHM) of 2.4 keV (4.0%) and 9.2 keV (1.4%), respectively. |
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Keywords: | CZT MASTRAP model Bridgman technique 2-MGE radiation detectors |
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