Shape control of electrodeposited copper films and nanostructures through additive effects

The use of electrolyte additives to affect nanocrystallite shape and film morphology in electrodeposited copper films is presented. Linear sweep and cyclic voltammetry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) methods are employed to investigate the effects of alcohol additives and the organic additive malachite green (MG), on copper electrodeposited onto polycrystalline gold electrodes. The use of additives affects the deposition process by increasing cathodic peak potentials and decreasing corresponding peak currents. Copper films deposited from electrolyte solutions with additives show additive-specific nanostructure and crystallite morphology. Film analysis reveals a greater than five times reduction in both film roughness and grain size in the presence of even small concentrations of the additive MG. Use of MG results in the preferential electrodeposition of oriented, square pyramidal crystallites, while alcohol additives result in tetrahedral crystallite textures. These shape-controlled additive effects are supported by additive adsorption energy calculations, which indicate preferential interactions, and differential growth kinetics on different facets of the film's growing nanostructures during electrodeposition. This approach offers a new and cost-effective route to achieve shape-controlled surface nanostructure.