STUDY OF CDTE ELECTRODEPOSITION FROM A NONAQUEOUS BATH

A detailed investigation has been carried out on the processes occurri ng during the electrodeposition of cadmium telluride on a nickel elect rode from a special bath containing CdCl2, TeCl4 and KI in ethylene gl ycol at 160-degrees-C. KI was added to the bath both to improve the de posit adhesion on the substrate and to hinder ion complexation. Steady -state current-potential and cyclic voltammetry experiments. were perf ormed along with electrolyte ohmic resistance measurements. The experi mental results evidenced the fairly good electrochemical behaviour of this organic electrolyte bath and its negligible ohmic resistance. Cyc lic voltammetry showed that the reduction of Te(IV) ions occurs via a four-electron process as well as a six-electron process followed by a chemical reaction. Moreover, during slow-scan cyclic voltammetry and s teady-state current-potential studies, the underpotential deposition o f Cd(II) ions was observed. This behaviour has been attributed to the negative Gibbs free energy change involved in the CdTe-forming reactio n.