Localized Surface Plasmon Resonance in Lithographically Fabricated Single Gold Nanowires

We report a study of localized surface plasmon resonance (LSPR) in single Au nanowires (NWs) created by atomic force microscopy nanolithography with widths and thicknesses of less than 110 and 30 nm, respectively, and lengths of a few micrometers. Two LSPR peaks at around 630 and 490 nm in wavelength are observed, and the intensity is strongest when the incident electric field is parallel to the length direction of a NW. The polarization dependence is due to the lack of well-defined axes in the cross section of a NW from transmission electron microscopy analysis. The current results are in strong contrast to previous results of lithographically fabricated NWs, in which a single resonance mode is observed and corresponds to electron oscillation along the width direction. The present work reveals the interesting variation of LSPR modes in single metal NWs that are potentially valuable for future plasmonic applications.