Electrodeposition of CdSe films: In-situ study by spectroscopic ellipsometry

CdSe films grown on Ti-coated polished steel by constant-current deposition from an aqueous solution containing selenosulfite and cadmium nitrilotriac etate have been studied by spectroscopic ellipsometry under in-situ conditi ons. Ellipsometric parameters, tan Psi and cos Delta, were measured both as a function of deposition time at lambda = 825 nm and of wavelength (lambda = 500-900 nm) for constant film thickness from 0.02 mu m to 2.3 mu m. The model used for data analysis, Ti-substrate \ TiO2 \ CdSe-film \ solution, w ith optically homogeneous phases was valid for film thickness larger than 0 .3 mu m Refractive indices and extinction coefficients of the 2.3-mu m film were derived for lambda = 500-900 nm. A direct band-gap of 1.72 eV was det ermined. The faradaic efficiency of electrodeposition was 0.93 for a curren t density of 50 mu A cm(-2).