NUCLEATION AND CRYSTAL-GROWTH IN GOLD ELECTRODEPOSITION FROM ACID-SOLUTION .1. SOFT GOLD

The initial stages of gold electrodeposition on a gold electrode were studied in a proprietary bath (Renovel N) using linear sweep voltammet ry and chronoamperometry. Tafel plots with two different slopes were o btained, indicating that the mechanism for gold deposition depends on potential. An inhibition phenomenon was observed during gold electrocr ystallization. Experimental current-time transients were analysed usin g nonlinear least-squares approximations by various models of nucleati on and crystal growth. The electrodeposition mechanism changes from th ree-dimensional progressive at lower overpotentials to three-dimension al instantaneous at higher overpotentials. Moreover, additional two-di mensional progressive or a secondary three-dimensional progressive pro cesses take place in certain potential ranges. It was shown that the o utward growth rate of the substrate's base plane displays a linear Taf el relationship whereas the vertical growth rate of gold crystals decr eases at more negative potentials due to an inhibition process.