Electrodeposition of Cu nanowire arrays with a template

Cu nanowire arrays were electrodeposited with a template of a polycarbonate (PC) filter. Pt–Pd alloy film was sputtered on one side of the PC filter and then used as cathode in 0.6 M CuSO4 aqueous solution (pH 2). Potentiostatic electrodeposition at −400 mV vs. Cu reference electrode was conducted in two kinds of electrolytic cell configurations, cathode over anode (C/A) and anode over cathode (A/C). The transient variation of the cathodic current clearly showed four stages in both cell configurations; (I) nucleation and crystal growth mode of Cu on the Pt–Pd film, (II) filling up with electrodeposited Cu in the nanosized pores, (III) covering of the surface of the template with Cu, and (IV) growth of a Cu thick film. In Stage II, the cathodic current increased in the A/C configuration, while it decreased in the C/A. The duration time of Stage II was shorter in the A/C configuration than that in the C/A. The difference of the cathodic current variation between the two configurations was smaller with smaller sized pores. These phenomena suggest that the ionic mass transfer rate of Cu2+ ion accompanied by electrodeposition is enhanced by a kind of natural convection even in and around such a nanosized pore and that the pores are filled up faster with electrodeposited Cu in the A/C than in the C/A configuration.