Double-resonance plasmon substrates for surface-enhanced Raman scattering with enhancement at excitation and stokes frequencies.

We report a surface-enhanced Raman scattering (SERS) substrate with plasmon resonances at both excitation and Stokes frequencies. This multilayer structure combines localized surface plasmons on the nanoparticles with surface plasmon polaritons excited on a gold film. The largest SERS enhancement factor for a gold device is measured to be 7.2 x 10(7), which is more than 2 orders of magnitude larger than that measured on a gold nanoparticle array on a glass substrate. The largest SERS enhancement for a silver device is measured to be 8.4 x 10(8).