Structural study of nanometric electrodeposited Co films using Co-59 NMR

A Co-59 NMR experiment has been used to investigate the structure of two se ries of Co films with thicknesses varying from 5 to 400 nm which were elect rodeposited on Cu at the electrolyte pH value of 2.1 and 3.7, respectively. It was shown that the overall structure of studied Co films consists of a very good quality fcc phase and a heavily faulted hcp phase in about equal proportions. The exceptions are very thin Co layers (below 20 nm) where the hcp structure was stabilized at pH 3.7 and overpotential of 0.9 V. This ef fect is attributed to the formation of hexagonal cobalt hydroxide in the ea rly stage of deposition, which acts as a buffer layer stabilizing Co hcp st ructure. (C) 2001 American Institute of Physics.