Plasmonic coupling of SiO2-Ag post-cap nanostructures and silver film for surface enhanced Raman scattering

We demonstrate a surface enhanced Raman scattering (SERS) substrate consisting of SiO2-Ag post-cap nanostructures with an underlying silver film fabricated by the glancing angle deposition technique. Electromagnetic simulations predict that SERS enhancement is strongly polarization-dependent, consistent with experimental measurements. Optimized coupling between Ag cap nanoparticles and the underlying silver film can be achieved by controlling the thickness of SiO2 post sandwiched between them to significantly enhance local electric-field intensity and to increase the density of electromagnetic hot spots. A maximum SERS enhancement factor of 2.38 X 10(9) within the hot spot region is demonstrated, providing sufficient sensitivity for many important applications. (C) 2011 American Institute of Physics. [doi:10.1063/1.3555342]