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ABSTRACT: In work the complex investigation of structural and optical properties of CdTe and Cd1-xMnxTe semiconductor films deposited by close-spaced vacuum sublimation method using thermal evaporation on non-oriented substrates was carried out. The structural and phase analysis of the layers condensed at different substrate temperatures was performed.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Proc. SPIE 8507, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics. 01/2012; 8507.
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A.E. Bolotnikov,
S. Babalola,
G.S. Camarda,
Y. Cui,
R. Gul,
S.U. Egarievwe, P.M. Fochuk,
M. Fuerstnau,
J. Horace,
A. Hossain,
F. Jones,
K.H. Kim,
O.V. Kopach,
B. McCall,
L. Marchini,
B. Raghothamachar,
R. Taggart,
G. Yang,
L. Xu,
R.B. James
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ABSTRACT: Poor crystallinity remains a major problem affecting the availability and cost of CdZnTe (CZT) detectors. Point defects are responsible for small gradual charge loss and correlated with the electron clouds' drift times, which allows electronic correction of the output signals to achieve high spectral-resolution even with large-volume CZT detectors. In contrast, extended defects causes significant charge losses, which typically are uncorrelated, and, thus, result in much greater fluctuations of the output signals that cannot be corrected. Although extended defects do not affect all the interaction events, their fraction rapidly increases with the crystal's thickness and volume. In this paper, we summarize our recent results from testing CZT material and detectors that emphasize the particular roles of two types of extended defects, and their contributions to the device's overall performance.
IEEE Transactions on Nuclear Science 09/2011; · 1.45 Impact Factor
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A.E. Bolotnikov,
S.O. Babalola,
G.S. Camarda,
H. Chen,
S. Awadalla,
Yonggang Cui,
S.U. Egarievwe, P.M. Fochuk,
R. Hawrami,
A. Hossain,
J.R. James,
I.J. Nakonechnyj,
J. Mackenzie,
Ge Yang,
Chao Xu,
R.B. James
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ABSTRACT: Large-volume CdZnTe (CZT) single crystals with electron lifetime exceeding 10 mus have recently become commercially available. This opened the opportunity for making room temperature CZT gamma-ray detectors with extended thicknesses and larger effective areas. However, the extended defects that are present even in the highest-quality material remain a major drawback which affects the availability and cost of large CZT detectors. In contrast to the point defects that control electron lifetime and whose effects on the charge collection can be electronically corrected, the extended defects introduce significant fluctuations in the collected charge, which increase with a crystal's thickness. The extended defects limit the uniformity in the electrons' drift distance in CZT crystals, above which electron trapping cannot effectively be corrected. In this paper, we illustrate the roles of the extended defects in CZT detectors with different geometries. We emphasize that the crystallinity of commercial CZT materials remains a major obstacle on the path to developing thick, large-volume CZT detectors for gamma-ray imaging and spectroscopy.
IEEE Transactions on Nuclear Science 09/2009; · 1.45 Impact Factor
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G Yang,
A E Bolotnikov, P M Fochuk,
G S Camarda,
Y Cui,
A Hossain,
K J Kim,
B Horace,
R Mccall,
L Gul,
O V Xu,
R B Kopach,
James
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J.K. Polack,
M. Hirt,
J. Sturgess,
N.D. Sferrazza,
A.E. Bolotnikov,
S. Babalola,
G.S. Camarda,
Y. Cui,
S.U. Egarievwe, P.M. Fochuk,
R. Gul,
A. Hossain,
K. Kim,
O.V. Kopach,
L. Marchini,
G. Yang,
L. Xu,
R.B. James
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ABSTRACT: Because of the low mobility of holes, CdZnTe (CZT) detectors operate as electron-transport-only type devices whose particular geometrical parameters and contacts configurations are specially chosen to minimize the contribution of uncollected holes into the output signal amplitudes (induction effect). Several detector configurations have been proposed to address this problem. One of them employs a large geometrical aspect ratio, parallelepiped-shaped crystal with two planar contacts on the top and bottom surfaces (anode and cathode) and an additional shielding electrode placed on a crystal’s side to create the virtual Frisch-grid effect. We studied the effect of the shielding electrode length, as well as its location, on the responses of 6×6×15 mm3 virtual Frisch-grid detectors. We found that the length of the shielding electrode placed next to the anode can be reduced to 5 mm with no adverse effects on the device performance. Meanwhile, this allows for charge loss correction by reading the cathode signals.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 621:424-430. · 1.21 Impact Factor
