Chemical etching and surface oxidation studies of cadmium zinc telluride radiation detectors

CdZnTe (CZT) is commonly used as a radiation detector material and the surface properties are important as they influence detector performance. The surface chemistry is generally controlled through chemical etching and oxidation processes. In this paper, X-ray photoelectron spectroscopy (XPS) is employed to investigate changes in the surface composition of single-crystal Cd0.95Zn0.05Te samples after exposure to bromine in methanol (BM) chemical etching treatments and subsequent oxidation in air or 30% H2O2. BM treatment of CZT is found to result in a graded Te-rich surface layer which increases in thickness as a function of BM concentration. Room-temperature air oxidation of 0.2% BM-treated CZT follows a logarithmic rate law. BM-treated CZT exposed to 30% H2O2 for 30 s shows a linear increase in the TeO2 oxide thickness with increasing BM concentration up to a BM concentration of 1.5%. Above 2% BM concentration, the Te enrichment in the CZT surface region has reached saturation and is effectively pure Te. Copyright (C) 2010 John Wiley & Sons, Ltd.