The kinetics of the electrodeposition of cadmium telluride

Abstract

The kinetics of the electrodeposition of CdTe from an aqueous solution containing CdSO₄, TeO₂ and H₂SO₄ were investigated by using a rotating ring-disc electrode. The results for tellurium deposition alone indicated that the reaction occurs through a six-electron reduction of HTeO₂⁺ to H₂Te, followed by a reaction between H,₂Te and HTeO₂⁺ yielding tellurium. At HTeO₂⁺ concentrations greater than 10^-3 M, the second step of this process is very fast and the overall reaction behaves as a four-electron reduction of HTeO₂⁺ to Te: only at lower HTeO₂⁺ concentrations was evidence observed for the six-electron reduction. The electrodeposition of CdTe occurs through two possible pathways: Cd²⁺ ions can react with H₂Te produced during the reduction of HTeO₂⁺ and thus yield CdTe, or tellurium deposited on the electrode can react with Cd²⁺ to yield CdTe. The two reactions compete with the deposition of pure tellurium. Conditions to deposit stoichiometric CdTe are suggested.