Adherent Cu films were electrodeposited onto polycrystalline W foils from purged solutions of 0.05 M CuSO4 in H2SO4 supporting electrolyte and 0.025 M CuCO3Cu(OH)(2) in 0.32 M H3BO3 and corresponding HBF4 supporting electrolyte, both at pH 1. Films were deposited under constant potential conditions at voltages between -0.6 V and -0.2 V vs. Ag/AgCl. All films produced by pulses of 10 s duration were visible to the eye; copper colored, and survived the Scotch tape test. Characterization by scanning electron microscopy (SEM)/energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of metallic Cu, with apparent dendritic growth. No sulfur impurity was observable by XPS or EDX. Kinetics measurements indicate that the Cu nucleation process in the sulfuric bath is slower than in the borate bath. In both baths, nucleation kinetics does not correspond to either instantaneous or progressive nucleation. Films deposited from 0.05 M CuSO4/H2SO4 solution at pH > 1 at -0.2 V exhibited poor adhesion and decreased Cu reduction current. In both borate and sulfate baths, small Cu nuclei are observable by SEM upon deposition at higher negative overpotentials, while only large nuclei (approx. 1 p,m or larger) are observed upon deposition at less negative potentials. (C) 2003 Elsevier Science B.V. All rights reserved.