ELECTRODEPOSITION OF ZINC TELLURIDE

The synthesis of polycrystalline thin films of cubic ZnTe by electrochemical plating on conducting substrates (titanium, nickel and F:SnO2 glass) is described. Electrodeposition involves potentiostatic reduction from an acid aqueous bath. The influence of bath composition (concentrations of the precursors TeO2 and Zn2+, and pH), deposition potential and temperature on the chemical composition of the films and on their crystallinity is discussed. The thin films were characterized by X-ray diffraction (XRD), electron probe microanalysis, scanning electron microscopy, and optical measurements. For optimized deposition parameters, the XRD pattern of a single-phase, cubic ZnTe was found. Otherwise, the patterns of either Zn or Te were found in addition in some samples. Best results (stoichiometric ZnTe films with a reddish aspect) were obtained from TeO2 saturated solution at a pH of 4.5, 98 degrees C, and a Zn2+ concentration of 0.02 M, employing deposition potentials between - 0.8 V and - 0.9 V vs. Ag/AgCl. The optical and crystalline properties of the films improved by annealing for 1 h at 450 degrees C in argon. By this treatment excess Te found in samples prepared under certain conditions could also be removed.