2, Northeastern University, Boston, Massachusetts, United States
3, Louisiana State University, Baton Rouge, Louisiana, United States
Template-assisted electrodeposited Fe-Ni-Co nanowires having an Invar-like composition (e.g. Fe-rich, with £ 5 wt % Co) are of interest for their low thermal expansion property, its ability to magnetically align nanowires, and to serve as a catalyst. The morphology of the nanowires is controlled by the deposition conditions (pulse vs dc), and with subsequent etching under the constraint when there is dissimilar structure or composition. Solid wires, tubular regions and novel porous structures were observed and controlled by the role of the hydrogen side reaction during deposition. Post treatment of nanowires via chemical etching, can also be used to shape the nanowires. Two different approaches were taken, 1) creating dissimilar crystalline structure within the nanowire by the choice of the deposition operating conditions followed by a select etch in structure and 2) introducing a sacrificial element, such as Cu, to selectively etch it in a passivating environment for Fe-Ni-Co. Unique thinned nanowires and nanotips were designed, and a kinetic Monte Carlo model was used to explain the role of the composition on the moment the wire breaks. In addition, Au decorated, Fe-Ni-Co nanowires were fabricated and the change in an individual wire electrical conductance determined in order to reflect the surface conditions.