Self-terminated Electrodeposition of Ni, Co and Fe Ultrathin Films
Thomas P. Moffat
Self-terminated iron group metal electrodeposition occurs at potentials negative of the onset of water reduction due to formation of a monolayer thick hydroxide layer. Quenching of metal deposition is accompanied by an increase in dissipative energy loss in microbalance experiments attributed to increased hydrogen bonding to the adjacent double layer. Pulse deposition at -1.5 VSSCE, in 5 mmol/L (NiCl2, CoCl2 or FeSO4) - 0.1 mol/L NaCl pH 3.0 electrolytes, yields smooth, fully coalesced ultrathin films of Ni, Co, Fe, or alloys thereof, on Au. The film thickness is determined by the nucleation, growth and termination dynamics constrained by the electrochemical cell time constant. Precipitation of bulk Ni(OH)2 and related phases is minimized by using short deposition times and dilute transition metal cation concentrations to limit supersaturation. The rapid deposition of smooth, compact ultrathin Fe, Co, Ni films should facilitate mechanistic and durability studies of Fe-group metal catalysis and the fabrication and operation of microdevices relevant to emerging technologies.
Journal of the American Chemical Society
self-terminated electrodeposition, electroplating, nickel, cobalt, iron