Abstract
Cadmium zinc telluride selenide (Cd1−xZnxTe1−ySey or CZTS) is one of the emerging CdTe-based semiconductor materials for detecting X- and gamma-ray radiation at or near room temperature (i.e., without cryogenic cooling). Potential applications of CZTS sensors include medical imaging, X-ray detection, and gamma-ray spectroscopy. Chemical passivation of CZTS is needed to reduce the conductivity of Te-rich surfaces, which reduces the noise and improves the device performance. In this study, we focus on the effect of surface passivation of CZTS using a 10% aqueous solution of ammonium fluoride. The effects of the chemical treatment were studied on the leakage current, charge transport measured as the electron mobility-lifetime (µτ) product, and the spectral resolution measured as the full-width at half-maximum (FWHM) of specific peaks. After passivation, the leakage current increased and began to decrease towards pre-passivation levels. The energy resolutions were recorded for eight applied voltages between −35 V and −200 V. The results showed an average of 25% improvement in the detector’s energy resolution for the 59.6 keV gamma peak of Am-241. The electron µτ product was unchanged at 2 × 10−3 cm2/V. These results show that ammonium fluoride is effective for chemical passivation of CZTS detectors.
Highlights
Cadmium zinc telluride selenide (CdZnTeSe or CZTS) has shown great potential as a quaternary semiconductor compound of cadmium telluride (CdTe) based materials for detecting nuclear radiation at room temperature [1,2,3]
The effects of the chemical treatment were studied on the leakage current, the charge transport measured as the electron mobility-lifetime product, and the spectral resolution of the detector for incident gamma rays
CdZnTe showed that NH4Ffor affects the includes current-voltage (I-V) curve and the energy resolution of the detector
Summary
Cadmium zinc telluride selenide (CdZnTeSe or CZTS) has shown great potential as a quaternary semiconductor compound of cadmium telluride (CdTe) based materials for detecting nuclear radiation at room temperature (i.e., without cryogenic cooling) [1,2,3]. Sensors 2019, 19, 3271 to defects that are related to large numbers of Te inclusions, subgrain boundaries, and compositional nonuniformity [8,9,10,11,12] These defects trap charges generated by absorption of radiation, limiting the charge transport abilities of the detector and resulting in lowering its performance for precise measurements of X- and gamma-ray energies [8]. This is especially critical in applications that require large-volume detectors [8,13]. This results in spatial variation of charge transport properties in CZT and is responsible for the spreading of pulse height in large-volume detectors [13]
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