Study of the spectral response of CZT multiple-electrode detectors

Cadmium zinc telluride (CZT) is a promising material for room temperature X-ray and gamma-ray detectors. The high atomic number and the wide band-gap give high quantum efficiency and good room temperature performances. Due to hole trapping, particular electrode structures have been developed to provide single-charge carrier collection (electrons), exploiting the excellent charge transport properties of the electrons. In this work, the spectroscopic performances of two CZT detectors (CZT1: 5 mm times 5 mm times 0.90 mm; CZT2: 4.8 mm times 5 mm times 0.55 mm) with five electrodes (cathode, anode and three steering electrodes) were studied. The anode-collecting electrode, surrounded by three steering electrodes (biased for optimum charge collection), is mostly sensitive to electron carriers, overcoming the effects of hole trapping in the measured spectra (hole tailing). We investigated on the spectroscopic response (241Am source; 59.5 keV) of the detectors at different bias voltages of the electrodes. The detectors exhibit excellent energy resolution (CZT1: 2.0% FWHM at 59.5 keV; CZT2: 1.7% FWHM at 59.5 keV; working temperature -10degC) and low tailing (CZT1: FW.1M to FWHM ratio of 1.93 at 59.5 keV; CZT2: 2.35 at 59.5 keV). This study stresses on the excellent spectroscopic properties of the CZT detectors equipped with a custom anode layout, making them very attractive candidates as x-ray spectrometers mainly for medical applications.