The Influence of Specific Anion Adsorption on the Surface Roughness of Electrodeposited Polycrystalline Cu Films

Abstract

We studied the effect of submillimolar quantities of specifically adsorbing anions on the surface roughness evolution of Cu films electrodeposited from acidic perchlorate electrolytes. Using scaling analysis, we found that the roughness evolution of the thin films galvanostatically deposited at constant overpotential in the presence of different anions is correlated with the anions’ adsorption energy. The roughness of the Cu films deposited in perchlorate electrolyte and the ones with the addition of nonadsorbing and weakly adsorbing anions follow almost the same anomalous scaling behavior. However, in the presence of specifically adsorbing halides, the roughness significantly changes, exhibiting near-normal scaling. This change is illustrated by a decrease in the local growth exponent, , with an increase in anion adsorption strength . The X-ray diffraction analysis showed the thickness-dependent change of the preferred microstructure orientation from {111} to {220} occurring at lower thicknesses in the presence of specifically adsorbing halides. Focused ion beam microstructure analysis also reveals columnar growth and larger grain size for films grown in the presence of specifically adsorbing halides. In this paper we show how the effects of specific adsorption on the mechanism of deposition and surface transport processes influence the changes in both roughness and microstructure evolution.