Nucleation kinetics and contact angles of silver clusters electrodeposited on indium tin oxide surfaces

The nucleation rate and the number density of nucleation sites, as well as the contact angle of silver clusters growing under diffusion control, have been determined with single-step potentiostatic experiments, from the electrical current and optical transmittance during electrocrystallization of silver on optically transparent indium tin oxide electrodes. It was found that silver grows at overpotentials as crystallites with an aspect corresponding to an effective contact angle with the indium tin oxide surface of ca. 13°. Comparison with results obtained from ex situ atomic force microscopy analysis suggests that electrodeposited nuclei undergo conformational relaxation at open circuit, leading to significantly higher equilibrium contact angles. The results obtained indicate that while the contact angles measured during growth at overpotentials have no bearing on the values of nucleation rates determined from the electrical and optical responses to potential steps, they lead to lower number densities of sites, in relation to values corresponding to the growth of hemispherical centers. Implications of the results obtained for the clustering of silver atoms leading to the electrocrystallization process are also discussed.