Shape and propagation rate of monatomic layers upon electrocrystallization of cadmium onto a screw-dislocation-free (0001) crystal face

Abstract

A screw-dislocation-free (0001) face on a cadmium single crystal was prepared by the capillary method in a cadmium sulphate solution. Successive current pulses due to spontaneous two-dimensional (2D) nucleation and growth were recorded at an overpotential close to the critical one (14–15 mV) for 2D nucleation. Statistical analysis of the time intervals between the successive pulses indicated a purely random and steady-state process of nucleation. Monatomic layers were deposited, each one from a single nucleus, at different overpotentials lower than the critical one for 2D nucleation. The analysis of the shape of the potentiostatic current transients recorded during deposition of the monolayers suggests that the growth shape of the layers is an equilateral triangle. The propagation rate of the monatomic layer was determined from each current transient. A linear dependence of the propagation rate on the overpotential was established. The kinetic constants of the deposition process of cadmium were determined.