VOLTAMMETRIC STUDIES OF TANTALUM ELECTRODEPOSITION BATHS

Deposits of tantalum were prepared at 780-degrees-C by reduction of K2TaF7, the solvent being a eutectic LiF-NaF mixture. Cyclic voltammetry and square-wave voltammetry were used to demonstrate the competition exerted on the reduction of the TaF7(2-) ions leading to deposition of tantalum oxide by reduction of the tantalum oxyfluoride ions [TaOF(n)(n-3), probably with n = 5]. The use of square-wave voltammetry enabled the attribution of a peak to each of the reactions and, from the peak current produced by TaF7(2-) its calibration curve to be established. This curve was used in monitoring the level of TaF7(2-) during the deposition process.