Oxidation and erosion of single crystal CdTe surface in distilled water and NaCl solution

Surface oxide formation was examined on low resistivity p-type CdTe single crystals immersed into distilled water held at 50 °C. The oxide thickness and roughness were investigated by spectroscopic ellipsometry, and its composition was studied by X-ray photoelectron spectroscopy. It was observed that after the fast growth of thin oxide layer with the thickness 1.7 nm the growth of oxide layer is proportional to a square root of the immersion time. The oxidation was described by a model in which the oxidation rate is limited by the drift of positive Cd ions from the CdTe-oxide interface into water. The penetration of Na and erosion of CdTe immersed in saturated NaCl solution was investigated by secondary ion mass spectrometry measurements on samples treated in NaCl solution for different time intervals. Very low determined diffusion coefficient of Na was explained by trapping of Na on acceptor-type defects in Cd sublattice.