Polarized surface enhanced Raman scattering from aligned silver nanowire rafts

Flat arrays (rafts) of aligned silver nanowires were fabricated by electrodepositing silver in the nanopores of highly ordered anodic alumina templates and then releasing the silver nanowires and depositing them on an oxidized, single-crystal silicon surface. SERS spectra were recorded from Rhodamine 6G molecules adsorbed onto the rafts. The SERS spectra showed striking polarization dependence according to the relative disposition of the E-vector with respect to the nanowires' axes. The observations can be adequately described by the classical electromagnetic (EM) response of the strongly interacting metal nanowires to the optical fields when surface plasmon resonances are induced. The discussion relates these observations to the origin of the giant surface enhanced Raman effect with single-molecule detectivity as well as to possible strategies that one might use to construct systems that predictably and repeatedly produce such giant EM fields.