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Electrochemical self-assembled of copper/copper oxide nanowires

S. Kenane and L. Piraux Unité de Physico-Chimie et de Physique des Matériaux, Place Croix du Sud 1, B-1348 Louvain-la-Neuve, Belgium

ABSTRACT Arrays of Cu/Cu 2 O nanowires are electrodeposited at room temperature from alkaline solutions of copper lactate in the nanopores of track-etched polymer membranes. Using the appropriate solution, the electrode potential spontaneously oscillates during the application of a constant cathodic current. Both the period of the oscillations and the composition of the nanowires can be controlled by varying the applied current density. A nanocomposite of copper and cuprous oxide is deposited at an applied current over which oscillations occur. In contrast, pure Cu or Cu 2 O nanowires are obtained at deposition current out of the range of oscillation. INTRODUCTION The fabrication of magnetic nanowires and multilayers has attracted considerable interest motivated by applications in the area of ultra-high density magnetic recording and by promising giant magnetoresistance and high-frequency properties [1-2]. Also, ultrathin superconducting wires exhibiting large critical field and anomalous resistive behavior have been investigated recently [3]. In addition, the template method was also employed for the synthesis of electrically conducting polymer tubules with conductivity of one order of magnitude larger than in the bulk form [4]. On the other hand, electrodeposited oxide/metal layered structures would be interesting because tunneling barrier effects could be studied. It was recently demonstrated that layered structures of copper/cuprous oxide can be prepared by electrodeposition [5-6]. The fabrication of multilayers by electrodeposition is usually made by pulsing the applied potential or current during the growth. However, it was shown that, using appropriate solution and pH, the electrode potential may spontaneously oscillate when a fixed current is applied. Evidence for layering was reported with individual thickness layers in the nanometer range [6-8]. The phase composition and layer thicknesses was found to be very sensitive to the applied current deposition and pH of the solution. In the present study, we report on the fabrication and properties of arrays of selfassembled Copper/Cuprous oxide nanowires made by electrodeposition in nanoporous tracketched polycarbonate membranes. These membranes are produced at the labscale and exhibit improved properties in terms of pore shape, pore size, porosity control and parallel arrangement of the pores [9]. The same fascinating phenomena already reported for films was also observed in the nanowire system, i.e., the electrode potential spontaneously oscillates during the application of a constant cathodic current. Our results provide new insight in the understanding of the oscillating phenomena. Electrical transport measurements were also recently reported in these Cu/Cu 2 O nanowires.[10]

AA6.2.1/M5.2.1

EXPERIMENTAL DETAILS Nanoporous membranes (22 microns thick) were used