Hg1-xCdxTe Surface after Chemical Etching and Electrochemical Reduction

Surface compositions of Hg1-x Cd x Te (MCT) after chemical etching and electrochemical reduction have been studied with an angle-dependent X-ray photoelectron spectroscopy (XPS) technique. The degree of oxidation formed after the chemical etching in Br2-methanol solutions is dependent on Br2 concentration but independent of etching time. The etched surface is Te-rich. The cation fraction x deviates from that of the bulk value. The oxides and accumulated elemental Te are eliminated from the etched surface by the reduction at -0.9 V vs Ag/AgCl for 1 h in pH 5.0 acetic-acetate solution. The cation/anion ratio and cation fraction x approach the bulk value and are constant in the depth. Furthermore, it is confirmed that the electrochemically reduced surface is more stable in atmospheric oxygen than the chemically etched MCT. This electrochemical reduction is used for treatment prior to surface passivation.