Study of the Nucleation and Growth Mechanisms in the Electrodeposition of Micro- and Nanostructured Cu2O Thin Films

In previous works, the electrochemical deposition method has been used to prepare pure Cu2O films onto titanium substrates from an aqueous cupric lactate solution. Recently, they have been shown to react reversibly with Li. The phase composition, the microstructure, and especially the surface morphology, crystal or grain size, and thickness of these films can be varied by changing the electrodeposition parameters. Because the characteristics of these films determine the electrochemical response toward Li+, a study of their kinetics and the mechanisms of the nucleation and growth will help us to understand fully their different reversibility behavior. Using three different applied potential values (-150, -400, and -575 mV), pure Cu2O thin films with varying surface morphologies and grain or crystal sizes were electrodeposited. Two- and three-dimensional nucleation models (instantaneous or progressive) under charge-transfer or diffusional growth control were used to describe the experimental potentiostatic current density-time transients to study the nucleation and growth mechanisms of as-prepared Cu2O films as a function of the surface morphology. The results obtained suggest a 2D layer-by-layer growth in parallel to a dependence-time 3D progressive nucleation process under charge-transfer control for the Cu2O thin films synthesized at E-d = -150 and -400 mV versus SCE. For the case of the films deposited at E-d = -575 mV versus SCE, the main contribution corresponds to a 3D progressive nucleation with diffusional control.