Integrated Fabrication and Magnetic Positioning of Metallic and Polymeric Nanowires Embedded in Thin Epoxy Slabs

This paper describes a process for the fabrication and positioning of nanowires (of Au, Pd, and conjugated polymers) embedded in thin epoxy slabs. The procedure has four steps: (i) coembedding a thin film of metal or conducting polymer with a thin film of nickel metal (Ni) in epoxy; (ii) sectioning the embedded structures into nanowires with an ultramicrotome ("nanoskiving"); (iii) floating the epoxy sections on a pool of water; and (iv) positioning the sections with an external magnet to a desired location ("magnetic mooring"). As the water evaporates, capillary interactions cause the sections to adhere to the substrate. Both the Ni and epoxy can be etched to generate free-standing metallic nanowires. The average translational deviation in the positioning of two nanowires with respect to each other is 16 ± 13 μm, and the average angular deviation is 3 ± 2°. Successive depositions of nanowires yield the following structures of interest for electronic and photonic applications: electrically continuous junctions of two Au nanowires, two Au nanowires spanned by a poly(3-hexylthiophene) (P3HT) nanowire; single-crystalline Au nanowires that cross; crossbar arrays of Au nanowires; crossbar arrays of Au and Pd nanowires; and a 50 × 50 array of poly(benzimidazobenzophenanthroline ladder) (BBL) nanowires. Single-crystalline Au nanowires can be placed on glass wool fibers or on microfabricated polymeric waveguides, with which the nanowire can be addressed optically.