Pulse Electrodeposition of Multi-Segmented Super Invar/Au Nanowires

Abstract

Nanowires are fabricated by template directed electrodeposition with multi-segmented nanowires with combined functionality. Five-segmented nanowires are developed in the sequence of: magnetic material, gold, sacrificial layer, gold, and magnetic material, to be used to create a nanogap electrode pair. The magnetic material was fabricated via pulsed electrodeposition of an alloy containing FeCoNi, the gold was deposited onto the FeCoNi, the sacrificial layer was Cu, and this layer was electrochemically etched in a citrate electrolyte that does not attack the other layers, particularly FeCoNi.

Editors' Choice—A Methodology to Electrochemically Fabricate Fe-Ni-Co Nanotips

“…[20][21][22][23] The reported nanotip materials used in AFM/STM are usually W and Pt/Ir, which are prepared through a "drop off" technique, where the tungsten wire is immersed in a KOH solution (etchant) acting as an anodic electrode; the highest etching rate appears just below the air/electrolyte interface, causing necking and eventual "drop off" of the bottom part of the wire, leaving a sharp tip. 14,17,19,24,25 Alternative methods for fabricating nanotips include: focused ion beam (FIB) lithography, 26 vapor-liquidsolid method (VLS), 27,28 and a novel, self-masking technique where SiC nanosized clusters are generated on top of a substrate, followed by a dry etch of the unmasked substrate regions to create nanotips where the SiC clusters reside.…”

Coupled, Simultaneous Displacement and Dealloying Reactions into Fe–Ni–Co Nanowires for Thinning Nanowire Segments

“…Figure a is a schematic of the procedure; a nanoporous, polycarbonate membrane (Whatman, porosity <15%, diameter 50 nm) is rendered conductive by sputtering gold on one side of it (Hummer IV, 15 mA, 70 mTorr, 5 min). A Fe–Ni–Co nanowire segment is first pulse electrodeposited, partially filling up the depth of the template, with conditions provided by Kim et al Fe–Ni–Co wires were pulsed deposited at −50 mA/cm 2 for 2 s and 0 mA/cm 2 for 2 s with the following electrolytes: 0.72 M nickel sulfamate, 0.155 M iron sulfate, 0.016 M cobalt sulfate, 0.5 M boric acid, 0.001 M sodium lauryl sulfate, and 0.011 M ascorbic acid at 40 °C. The partially filled template is dipped into an acid solution containing copper ions to cause displacement, corrosion, and dealloying of the Fe–Ni–Co alloy.…”

Template-Assisted Electrodeposition of Porous Fe–Ni–Co Nanowires with Vigorous Hydrogen Evolution

“…For the reduction of noble metal ions, conditions can be selected to avoid the hydrogen side reaction from both proton reduction and the water splitting reaction; however, for non-noble metal ion reduction, such as Fe­(II), Ni­(II), and Co­(II), their reduction occurs in the region where hydrogen gas evolution cannot be avoided. Strategies that have been used to circumvent pore blockage by gas bubble growth is to use pulse plating that provides time for diffusion of gas bubbles out of the pores and species redistribution, − as well as using a surfactant that reduces surface tension to avoid gas bubbles blocking the electrode surface. − If gas bubbles can be deterred from growing and coalescing but remain at the electrode surface to act as an additional template within the nanotemplate, it is possible to directly deposit a porous nanowire without the subsequent etching step needed. Presented here is the first demonstration of porous Fe–Ni–Co nanowires prepared directly by electrodeposition without a subsequent etching step.…”