Potentiostatic controlled nucleation and growth modes of electrodeposited cobalt thin films on n-Si(1 1 1)

Abstract

The nucleation and growth of Co electrodeposits on n-Si(111) substrate have been investigated as a function of the applied potential in a large potential range using electrochemical techniques (voltammetry and chrono-amperometry) and surface imaging by Atomic Force Microscopy (AFM). The surface preparation of the sample is crucial and we achieve a controlled n-Si(111) surface with mono-atomic steps and flat terraces. We observe an increase of the Co yields in the electrodeposition process with the potential due to a lower contribution of hydrogen release at higher overpotentials. Using Scharifker-Hills models for fitting the current-time transients, we show that a transition from an instantaneous nucleation process to a progressive one occurs when the overpotential increases. We show A good agreement between the nucleation and growth parameters extracted from the models and the AFM data's is observed. The growth is of the Volmer-Weber type with a roughness and a mean diameter a spatial extension in the substrate plane of the deposited islands that increase with thickness.