Fabrication of Functional Metallic Nanowires Using Electrodeposition Technique

The array of numerous metallic nanowires with straight shape has much attention due to their shape anisotropy and extremely large surface area. This unique structure can be applied to develop the novel functional nano-materials such as electronic, magnetic and optical nano-scale devices. Metallic nanowires can be fabricated by manipulating metallic atoms one by one using a scanning tunneling microscope (STM) probe, while they can be also prepared by electrochemically depositing metallic atoms into a nanoporous template with numerous cylindrical nanopores. In a fabrication technique using electrodeposition of nanowires, nanoporous templates such as anodized aluminum oxide films with high density of nanopores (about 108~1010 pores•cm–2) have been used so far. In 1975, using an anodic oxide coating film on aluminum, magnetic properties of electrodeposited Co nanowires and Co-Ni alloy nanowires were investigated (Kawai & Ueda, 1975). In 1986, as an application to perpendicular magnetic recording medium, alumite films containing Fe nanowires were fabricated (Tsuya et al., 1986). In 1988, magnetization curling process in perpendicular direction was studied using Fe nanowire arrays in alumite media (Huysmans et al., 1988). In 1990, influence of the packing density on the magnetic behaviour was investigated using alumite media containg magnetic nanowires (Zhang et al., 1990). On the other hand, in 1991, using the polymer membrane template with numerous nanopores, polymeric and metal microtubules were synthesized (Martin, 1991). In 1993, arrays of Ni and Co nanowires were electrodeposited in polymer templates with the nanometer-sized pores prepared by nuclear track etching technique (Whitney et al., 1993). They found that the preferred magnetization direction is perpendicular to the film plane and enhanced coercivities as high as 680 Oe. Remnant magnetization of the nanowires up to 90% had been reported. In 1994, a membrane-based synthetic approach to obtain nanomaterials was introduced to materials science field (Martin, 1994). He suggested that the template synthesis method is useful to prepare polymers, metals, semiconductors, and other materials on a nano-scopic scale. In 1994, giant magnetoresistance (GMR) properties were found in Co/ Cu multilayered nanowires electrodeposited in nanoporous polymer template (Piraux et al., 1994). In the report, magnetoresistance measurements with the current perpendicular to the layers were performed on the array of parallel nanowires. They observed that the 15% of GMR at room temperature on Co/ Cu multilayered nanowires. In the almost same time, GMR of