The PC porous membranes with interconnected pores have been fabricated by exposing a 22-μm-thick PC film to a two-step irradiation process. The topology of the membranes was defined by exposing the film to a first irradiation step at two fixed angles of −25° and +25° with respect to the normal axis of the film plane. After rotating the PC film in the plane by 90°, the second irradiation step took place at the same fixed angular irradiation flux to finally form a 3D nanochannel network. The diameter of the latent tracks was enlarged by following a previously reported protocol to obtain membranes with distinct porosities and pores sizes (37 ). The PC membranes with average pore diameters of 80 and 105 nm display low volumetric porosity (3%) and large volumetric porosity (22%), respectively. Next, the PC templates were coated on one side using an e-beam evaporator with a metallic Cr/Au bilayer to serve as cathode during the electrochemical deposition. The thickness of the thin adhesion layer of Cr was 3 nm, while for a uniform and consistent nanopore coverage withstanding the electrodeposition process, the Au film thickness was set to 400 and 750 nm for the 80- and 105-nm-diameter porous membranes, respectively.
The multilayered NW networks have been grown at RT by electrodeposition into the 3D porous PC templates from a single sulfate bath using potentiostatic control and a pulsed electrodeposition technique (38 ). For these experiments, we used an Ag/AgCl reference electrode and a Pt counter electrode. To prepare the CoNi/Cu interconnected NW networks, the composition of the electrolyte was 2.3 M NiSO4 · 6H2O + 0.4 M CoSO4 · 7H2O + 15 mM CuSO4 · 5H2O + 0.5 M H3BO3, and the deposition potential was alternatively switched between −1 V to deposit equiatomic CoNi alloy layer (containing approximately 5% Cu impurity), and −0.4 V to deposit almost pure Cu layers (39 ). Following a procedure described elsewhere (38 ), the deposition rates of each metals were determined from the pore filling time. According to this calibration, the deposition time was adjusted to 300 ms and 12 s for the CoNi and Cu layers, respectively, and the estimated average thickness of the bilayer was ~15 nm, with approximately the same thicknesses for the CoNi and Cu layers. The morphology of the nanostructured interconnected NW networks was characterized using a high-resolution field emission SEM JEOL 7600F equipped with an energy-dispersive x-ray analyzer. For the electron microscopy analysis, we removed the PC template by chemical dissolution using dichloromethane. For conducting magnetotransport measurements, the cathode was locally removed by plasma etching to create a two-probe design suitable for electric measurements, with the flow of current restricted along the NW segments, thus perpendicular to the plane of the layers.
The multilayered NW networks have been grown at RT by electrodeposition into the 3D porous PC templates from a single sulfate bath using potentiostatic control and a pulsed electrodeposition technique (38 ). For these experiments, we used an Ag/AgCl reference electrode and a Pt counter electrode. To prepare the CoNi/Cu interconnected NW networks, the composition of the electrolyte was 2.3 M NiSO4 · 6H2O + 0.4 M CoSO4 · 7H2O + 15 mM CuSO4 · 5H2O + 0.5 M H3BO3, and the deposition potential was alternatively switched between −1 V to deposit equiatomic CoNi alloy layer (containing approximately 5% Cu impurity), and −0.4 V to deposit almost pure Cu layers (39 ). Following a procedure described elsewhere (38 ), the deposition rates of each metals were determined from the pore filling time. According to this calibration, the deposition time was adjusted to 300 ms and 12 s for the CoNi and Cu layers, respectively, and the estimated average thickness of the bilayer was ~15 nm, with approximately the same thicknesses for the CoNi and Cu layers. The morphology of the nanostructured interconnected NW networks was characterized using a high-resolution field emission SEM JEOL 7600F equipped with an energy-dispersive x-ray analyzer. For the electron microscopy analysis, we removed the PC template by chemical dissolution using dichloromethane. For conducting magnetotransport measurements, the cathode was locally removed by plasma etching to create a two-probe design suitable for electric measurements, with the flow of current restricted along the NW segments, thus perpendicular to the plane of the layers.
