Template Synthesis of Au/Co Multilayered Nanowires by Electrochemical Deposition

• Published in: Advanced functional materials 2002, Vol.12 (11-12), p.766-772
• Main Authors: Valizadeh, S., Hultman, L., George, J.M., Leisner, P.
• Format: Article
• Language: English
• Subjects: Electrochemical fabrication; metal; multilayers; Nanostructures; Nanostructures, multilayers; Nanowires; Nanowires, metal, Au, Co; TECHNOLOGY; TEKNIKVETENSKAP; Template-directed synthesis
• ISSN: 1616-301X; 1616-3028; 1616-3028
• DOI: 10.1002/adfm.200290005

The electrochemical deposition of Au/Co multilayers into 20 μm‐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 multilayered nanowires revealed dense and well‐defined layer interfaces. X‐ray diffraction investigations of 20 μm long Au and Co nanowires showed that the Au deposits exhibit a face‐centered cubic (fcc) 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. Au/Co multilayers have been deposited into 20 μm thick ion track etched polycarbonate membranes. The optimal conditions for the electrodeposition of these multilayers have been determined by cyclic voltammetry, chronoamperometry, and pulse‐potential experiments in different electrolytes. A dark field TEM image from 2 nm Au/4 nm Co multilayered nanowires reveals dense and well‐defined layer interfaces (see Figure).