Fabrication and characterisation of copper nanowires electrochemically deposited in etched ion-track membranes
Poly- and single-crystalline copper nanowires have been created by electrochemical deposition of copper in etched ion-track membranes. 30 µm thick polycarbonate foils were irradiated at the UNILAC (GSI, Darmstadt) with Au and Pb ions of kinetic energy 1-2 GeV with ?uences between 1 and 10^9 ions/cm^2. The latent tracks generated by the heavy ions were chemically etched providing membranes with cylindrical pores of diameter between 30 nm and µm. These membranes were used as templates for the growth of copper. Potentiostatic deposition of copper in membranes with large (several hundred nm) and small (several ten nm) diameter pores have been investigated using a two-electrode electrochemical cell. We present the results of a systematic study aimed at determination of the optimal deposition parameters (overvoltage, temperature, and electrolyte solution) required for single-crystalline growth. The morphology and crystallinity of the copper nanowires were studied by means of scanning electron microscopy, transmission electron microscopy and x-ray diffraction. Thus, from our results we can afirm that nanowires deposited at high temperatures (50 ?C) and overvoltages lower than 60 mV possess a single-crystalline structure. Polycrystalline wires were obtained from deposition at room temperature or at higher overvoltages. Typical defects of single- crystals as twins and slips were also observed. Two different techniques were tested to contact nanoneedles for electrical transport measurements.
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