Advanced Functional Materials, Vol.12, No.11-12, 766-772, 2002
Template synthesis of Au/Co multilayered nanowires by electrochemical deposition
The electrochemical deposition of Au/Co multilayers into 20 mum-thick ion track etched polycarbonate membranes with pore diameters of 110-150 nm was studied in a single electrolyte containing cobalt sulfate, gold cyanide, and citric acid. Cyclic voltammetry, chronoamperometry, and pulse-potential experiments were used to determine the deposition conditions for pure Au and 98 wt.-% Co layers. The Co-rich metallic nanowires were deposited at -1100 mV and the Au nanowires at -490 mV vs. Ag/AgCl. Under open-circuit conditions an Au-displacement reaction occurred. Open-circuit conditions were applied in combination with a steep ramp between the Co and Au potential pulses to avoid the otherwise severe Co-dissolution when the potential was switched to less negative values. Scanning and transmission electron microscopy of the deposited multilayers nanowires revealed dense and well-defined layer interfaces. X-ray diffraction investigations of 20 mum long Au and Co nanowires showed that the Au deposits exhibit a face-centered cubic (fcc) <111> texture, while the Co deposits exhibit a hexagonal close-packed (hcp) (002) structure. The magnetic measurements of 12 nm Co/4 nm Au nanowires for fields applied parallel and perpendicular to the film plane indicate a low remnant magnetization.