Real-Time Pulse Height Spectroscopy Using Cd0.9Zn0.lTe Coplanar Grid Digital Spectrometer

Detector grade large volume Cd0.9Zn0.1Te (CZT) single crystals were grown using a modified vertical Bridgman technique. Single crystals of dimensions 1.1 × 1.1 × 1.0 cm
³
were used to fabricate detectors in coplanar grid (CG) geometry. The CG-CZT detectors were characterized using various electrical, optical and spectroscopic techniques. Current-voltage (I- V) measurements were carried out in planar configuration at room temperature. The bulk resistivity was found to be 3.3 × 10
¹⁰
Ω-cm. Intergrid I-V measurements were also carried out and the intergrid leakage current was found to be negligible under the operating conditions. IR transmission images showed the presence of tellurium (Te) inclusions with an average diameter of 8 μm, A digital data acquisition program was developed to collect the preamplifier charge pulses connected to the two grids and plot the difference spectrum to obtain single-polarity charge sensing pulse-height spectra in real time. The detector was exposed to a
¹³⁷
Cs radiation test source emitting 662 keV gamma rays and well-resolved digital gamma pulse height spectra were generated.