Detector grade Cd0.9Zn0.1Te (CZT) single crystals were grown from zone refined Cd, Zn, and Te (∼7 N) precursor materials, using a telluriumsolvent method. Detectors with virtual Frisch grid configuration were fabricated using these crystals. I-V measurements revealed low leakage currents at room-temperature, ∼11 nA for one such detector D1 and ∼8 nA for another detector D2 at 1100 V. The spectroscopic performances of the two CZT virtual Frisch grid detectors have been evaluated and compared for high energy gamma ray detection.Detector D1 showed a well-resolved pulse-height spectrum with an energy resolution of ∼1.6% for the 662 keV gamma rays.Detector D2 also showed a distinct 662 keV peak but with a broader pulse-height distribution. A digital biparametric correlation study of the depth of interaction and energy deposited by the 662 keV gamma rays was carried out. A different kind of correlation pattern from that observed normally for hole trapping was noticed in the case of detector D2. Correlation of results from thermally stimulated current measurement studies suggested that the anomalous biparametric correlation pattern was due to the trapping of holes but modified by the virtual Frisch grid effect. The results also suggested that the effect of electron trapping could not be ruled out either. Finally, a digital correction scheme was applied to recover the 137Cs spectrum from the effect of charge loss.
Received 20 December 2012Accepted 08 February 2013Published online 21 February 2013
This research was performed using partial funding received from the DOE Office of Nuclear Energy's Nuclear Energy University Programs (Grant No. DE-AC07-05ID14517).
Article outline: I. INTRODUCTION II. EXPERIMENTAL METHODS A. Detector fabrication B. Detector characterization C. Digital spectroscopic measurements III. RESULTS AND DISCUSSIONS A. I-V characteristics B. Gamma ray measurements IV. CONCLUSIONS
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