Electrodeposition of ZnTe Film with High Current Efficiency at Low Overpotential from a Citric Acid Bath

The cathodic electrodeposition of ZnTe film was studied using an aqueous citric acid bath (pH 4; temperature 368 K) in which Zn(II) and Te(IV) species were dissolved to form Zn(Cit)₂ ^4- and HTeO ₂ ⁺ ions, respectively. The deposition mechanism was studied based on cyclic voltammetry. The influence of the deposition potential on the morphology, composition, and structure of the deposited film was also investigated. A smooth, dense polycrystalline ZnTe film with nearly stoichiometric composition was deposited at a constant cathode potential, ranging from -0.80 to -0.60 V vs. Ag/AgCl, from a solution containing 20 mmol dm^-3 Zn(II), 0.16 mmol dm^-3 Te(IV), 0.25 mol dm ^-3 H₃Cit, and 0.25 mol dm^-3 Na₃Cit (Cit = C₆H₅O₇). Potentials in this range provided the deposited ZnTe film with high current efficiency (above 98%). During electrodeposition of the nearly stoichiometric crystalline ZnTe, the current density was approximately stationary.