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Cadmium zinc telluride selenide (CdZnTeSe) has shown great promise in reducing the cost of semiconductor nuclear detectors that can operate at room temperature without cryogenic cooling. This is due to the high yield of detector-grade materials in the CdZnTeSe crystal growth process, which can be attributed to the much smaller numbers of Te inclusions and grain boundary network in CdZnTeSe compared to other CdTe-based semiconductors such as CdZnTe. In the present work, we study the effects of surface passivation on CdZnTe detectors using a mixture of ammonium fluoride and hydrogen peroxide solution (NH4F + H2O2 + H2O). Detectors fabricated from CdZnTeSe crystals showed very good energy resolutions: 1.1% for the 662-keV gamma peak of Cs-137 by Frisch-grid detectors, and 5.9% for the 59.6-keV gamma peak of Am-241 by planar detectors. Experimental results show that the leakage current is increased immediately after passivation and then decreases as the surfaces stabilizes. The resistivity of the CdZnTeSe is of the order of 10**10 Ω-cm. The surface passivation improved the energy resolution of planar detector by 18% for the 59.6-keV gamma peak of Am-241. 

High-resistivity zinc cadmium telluride (CdZnTe) semiconductor is a very popular material for room-temperature nuclear detection applications. It is used for the detection of X-rays and gamma rays in many areas: nuclear and radiological threat detection, medical imaging, gamma spectroscopy, and astrophysics. Mechanical stability at the interface of electrical contacts and the detector material is an important factor in terms of durability and shelf life of detector devices. Other engineering factors where that interface plays an important role include thermal expansion due to temperature changes and vibrations that may result from certain applications. The surface composition of the material play an important role in the surface stability of the material. The stoichiometric composition of the detector surfaces also affects its surface current, which, in turn, contributes to electronic noise. High electronic noise is detrimental to the energy resolution of the detector device. X-ray photoelectron spectroscopy (XPS) is a good technique for determining dominant surface composition of materials. In this current study, the authors used an XPS to look at the dominant composition materials on the surface of a CdZnTe wafer. The experiments involved loading CdZnTe wafers into the XPS machine and recording the peaks of the binding energies of elements and compounds present on the surfaces. The XPS results showed the presence of Zn, Te, O, Cd, C, Cl, Si, and TeO2. These results are important in the engineering of CdZnTe radiation detection devices. 

Cadmium telluride (CdTe) and its ternary and quaternary compounds have found applications in the development of X-ray and gamma-ray detectors used in nuclear detection and medical imaging applications. Example of these detectors include CdZnTe (CZT), CdMnTe (CMT), and CdZnTeSe (CZTS). These nuclear detectors can operate at room temperature without cryogenic cooling. This paper presents comparative studies of these semiconductor material. The properties studied include detector resistivity, Te inclusions, grain boundary networks, mobility/lifetime of the charge carriers, and energy resolution. The effects of passivation with chemicals such as KOH and NH4F, are also presented. X-ray photoelectron spectroscopy (XPS) studies showed increase in the quantity of TeO2 on surfaces of these materials after passivation in KOH and NH4F. While CZT detector has wide commercial availability, it has more Te inclusions and grain boundary network compared to CZTS. CMT and CZTS have better crystal uniformity than CZT. The comparatively low presence of Te inclusions and grain boundary network in CZTS gives it a higher crystal growth yield for detector-grade material. 

Cadmium manganese telluride (CdMnTe) crystals are expected to be homogeneous in structure due to the segregation coefficient of Mn in CdTe, which is about 1.0. This could translate in the growth of large-volume CdMnTe crystals free of defects that currently limit X-ray and gamma-ray detection efficiencies. The present characterization experiments show results on CdMnTe planar detectors grown by the vertical Bridgman technique. The CdMnTe crystal used in the experiments was mostly free of tellurium inclusions and high angle grain boundaries. We recorded an energy resolution of 9.2% FWHM for the 59.5-keV gamma-peak of Am-241 for the planar detector. We also resolved peaks at energies below the 59.5-keV peak.