STUDY OF GOLD DEPOSITION ON COPPER BY ELECTROCHEMICAL AND MICROSCOPICTECHNIQUES

Deposition of gold on copper from acid gold bath was investigated usin g electrochemical and microscopic techniques. The growth morphology of both soft and hard gold deposits was characterized using scanning ele ctron microscopy (SEM) and atomic force microscopy (AFM). Analysis of chronoamperometric transients showed that the mechanism of nucleation and growth of hard gold is three-dimensional progressive nucleation an d growth of right-circular cones. This was further confirmed by SEM an d AFM measurements. The grain size of hard gold deposit was shown to b e much smaller than that of soft gold, indicating that nickel in depos it acts as a grain refiner. The mean roughness of hard gold deposit in creases with deposition time, and with an increase of negative potenti al from -0.5 to -0.70 V (vs SCE), however, the surface becomes more un iform at -0.80 V. Similarly, the maximum height of clusters increases as potential is made more negative between -0.50 and -0.65 V, while it decreases steeply at potentials from -0.65 to -0.80 V. The inhibition of crystal growth in gold deposition at certain potentials was observ ed electrochemically and corroborated by microscopic techniques.