Freestanding nanowire arrays from soft-etch block copolymer templates

Nanoporous poly(4-fluorostyrene) templates on gold-coated silicon/silicon oxide substrates were prepared by the electric field alignment of poly(4-fluorostyrene)-b-poly(d,l-lactide) block copolymer thin films followed by mild degradation of the polylactide phase using dilute aqueous base. Electrochemical deposition of nanowires was accomplished using a protocol for the preparation of copper oxide. Freestanding nanowires were observed after removal of the template by either simple dissolution of the poly(4- fluorostyrene) or by treatment with UV irradiation. The annealing time, the electric field strength used to align the block copolymer films, and the template removal method are shown to influence the freestanding nanowire arrays. The "soft-etch" method described is generally useful for the preparation of templates and nanostructures that are sensitive to more aggressive template removal processes.