A NOVEL GOLD ELECTROPLATING SYSTEM - GOLD(I)-IODIDE-THIOSULFATE

The electrodeposition of gold from a new electroplating system for gol d that contains iodide and thiosulfate has been studied using rotating disk voltammetry. The cathodic electron transfer is slow, with a tran sfer coefficient of alpha = 0.76 +/- 0.02, and is coupled with a prece ding chemical reaction, the formation of the complex ion Au(S2O3)(2)(3 -). The magnitude of the current contribution from the chemical step c an be made negligible by using high concentrations of thiosulfate and by the proper choice of supporting electrolyte. High quality gold depo sits with a very high aspect ratio have been obtained through a photor esist mask from this plating bath under optimized conditions. The choi ce of univalent salt as supporting electrolyte affects markedly the el ectroreduction of Au(I).