Electrochemical pore filling strategy for controlled growth of magnetic and metallic nanowire arrays with large area uniformity

Abstract

While a variety of template-based strategies have been developed in the fabrication of nanowires (NWs), a uniform pore filling across the template still poses a major challenge. Here, we present a large area controlled pore filling strategy in the reproducible fabrication of various magnetic and metallic NW arrays, embedded inside anodic aluminum oxide templates. Using a diffusive pulsed electrodeposition (DPED) technique, this versatile strategy relies on the optimized filling of branched nanopores at the bottom of templates with Cu. Serving the Cu filled nanopores as appropriate nucleation sites, the DPED is followed by a uniform and homogeneous deposition of magnetic (Ni and Fe) and metallic (Cu and Zn) NWs at a current density of 50 mA cm for an optimal thickness of alumina barrier layer (∼18 nm). Our strategy provides large area uniformity (exceeding 400 μm) in the fabrication of 16 μm long free-standing NW arrays. Using hysteresis loop measurements and scanning electron microscopy images, the electrodeposition efficiency (EE) and pore filling percentage (F ) are evaluated, leading to maximum EE and F values of 91% and 95% for Ni and Zn, respectively. Moreover, the resulting NW arrays are found to be highly crystalline. Accordingly, the DPED technique is capable of cheaply and efficiently controlling NW growth over a large area, providing a tool for various nanoscale applications including biomedical devices, electronics, photonics, magnetic storage medium and nanomagnet computing.

Small-diameter magnetic and metallic nanowire arrays grown in anodic porous alumina templates anodized in selenic acid

“…But in the following, it has immediately increased and remained constant, whereas the reduction voltage of the sample thinned in oxalic acid decreases progressively. Based on previous works, the progressive reduction of this voltage is necessary to reach optimum and uniform electrodeposition [46]. Also, by performing the PED, the presence of the oxidation half cycle leads to an increase in the barrier layer resistivity [50].…”

“…To electrodeposit such a sample, the concentration of electrolyte solutions was set as follows: CoFeNi pre-plating) [45], prior to the electrodeposition of Zn nanowires. Other conditions for each element were set according to the optimal conditions reported previously [46]. The magnetic properties of the prepared nanowires were measured using a vibrating sample magnetometer (VSM, Magnetic DaneshPajoh Kashan Co.) at room temperature with an applied field parallel to the nanowire axis.…”

“…04-0783). The absence of Ni peaks in the XRD pattern of AgNi nanowires can be related to the additive role of Ni during the electrodeposition due to its low content arising from the smaller valence of Ni than that of Ag [46]. Moreover, the more positive standard reduction potential of Ag (+0.8 V) than that of Ni (-0.25 V) can lead to the domination of the electrodeposition of Ag.…”

Small-Diameter Magnetic and Metallic Nanowire Arrays Grown in Anodic Porous Alumina Templates Anodized in Selenic Acid

“…But in the following, it has immediately increased and remained constant, whereas the reduction voltage of the sample thinned in oxalic acid decreases progressively. Based on previous works, the progressive reduction of this voltage is necessary to reach optimum and uniform electrodeposition [46].…”

Template-Assisted Iron Nanowire Formation at Different Electrolyte Temperatures

“…Because of their biocompatibility, neutrality, and easy intracellular digestion [ 50 ], unlike Ni- and Co-containing nanostructures, iron nanowires are attractive materials for chemical and biomedical applications [ 17 ]. The crucial problem during nanowire deposition is the pore filling efficiency, which can be controlled by chemical agents, the electrodeposition rate, or other electrodeposition parameters such as pH, temperature, electrolyte composition, values of cathodic potential, or current [ 51 , 52 , 53 ]. In the presence of air, iron nanowires naturally develop an oxide layer on their surface, which makes them biocompatible and biodegradable, but that results in limitations in their sensor-like applications; thus, preventing the uncontrollable oxidation of nanowires is another challenge in the production of Fe nanowires [ 26 ].…”