Comparative study on the effects of chemical treatments on CdZnTe nuclear detectors

Room temperature semiconductor detectors such as cadmium zinc telluride (CdZnTe) are often subject to surface damage during fabrication processes, thus affecting detector performance. The surface defects are usually removed through mechanical and chemical polishing, and passivation processes. This paper compares the effects of two surface passivation chemical solutions on CdZnTe detectors. The two chemicals studied are ammonium fluoride in hydrogen peroxide (NH₄F + H₂O₂ + H₂O) and potassium hydroxide in hydrogen peroxide (0.1 g of KOH + 10 ml of 30% H₂O₂) solutions. X-ray photoelectron spectroscopy analysis showed that the NH₄F-based solution is more effective at converting Te species on the CZT wafer surfaces into a more stable TeO₂ layer, with values of 4.90 and 5.34 for the Te₃d_3/2O₂/Te₃d_3/2 and Te₃d_5/2O₂/Te₃d_5/2 peak-height ratios respectively, compared to the KOH-based solution which has 1.25 and 1.19 respectively. Analysis of the 59.5-keV peak of Am-241 showed that the sample passivated with the NH₄F-based solution has a better energy resolution (FWHM = 9.83%) compared to the one passivated with the KOH-based solution (FWHM = 14.60%).