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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. 

Cadmium zinc telluride (CdZnTe) and cadmium manganese telluride (CdMnTe) semiconductor nuclear detectors have the ability to operate at room temperature without cryogenic cooling. Thus, they can be fabricated into portable nuclear detection devices that can be used at seaports and border security, and at nuclear facilities to monitor radiation levels. In this paper, we present results from the use of X-ray photoelectron spectroscopy (XPS) to study the surface compositions of CdZnTe and CdMnTe wafers. Our results showed that Cd, Te and TeO2 are the dominant species on these materials. Zn was also present on CdZnTe wafer, and Mn is present on the CdMnTe wafer. CdZnTe samples that were etched with high-energy ion beam did not show the presence of TeO2 on their surfaces. 

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.