Electrochemical nucleation and optical characterization of highly oriented Bi clusters on Cu substrate

Abstract

The electrochemical nucleation and growth of bismuth (Bi) crystallites on copper substrates were investigated using cyclic voltammetry and chronoamperometry measurements, and scanning electron microscopy (SEM). The experimental current transients were analyzed according to the Scharifker and Hills and Mirkin-Nilov and Heerman-Tarallo models. At relatively low overpotentials and low Bi concentration, Bi deposition can be described by a model involving progressive nucleation on active sites and 3D diffusion-controlled growth. At higher Bi concentration, the growth mechanism shifts to the instantaneous nucleation mode. These results were also confirmed by SEM analysis. The values of some kinetic parameters such as the nucleation rate, the number density of active sites and the diffusion coefficient of Bi3+ ions were also calculated using different theoretical approaches. X-ray diffraction measurements revealed that the Bi crystallites grow in the rhombohedral crystal structure along the [012] direction. The optical properties of the dispersed Bi nanoparticles on the Cu surface were discussed in the ultraviolet-visible (UV–Vis) wavelength range. It was found that the UV–Vis spectrum exhibit a strong resonant optical absorption on the surface with the smallest Bi crystallite size (200 nm).