Surface enhanced Raman microscopy with metal nanoparticle arrays

We present high-resolution images of surface enhanced Raman scattering (SERS) from Rhodamine 6G homogeneously adsorbed on periodic arrays of square gold nanostructures, fabricated with electron-beam lithography on the top of a smooth gold film and having surface plasmon resonances close to the 532 nm excitation wavelength. We use reflection spectroscopy to map the resonances and present the first (to our knowledge) point-by-point comparison of SERS spectra from locations separated by submicron distances within nanoparticle arrays, establishing good correspondence of the spectral resonance shape with the spectral dependence of local SERS enhancements and qualitatively comparing SERS images for different spectral frequency ranges. These results illustrate that, in addition to considering only the well established approximation of vertical bar E vertical bar(4)-dependence of the surface enhanced Raman signal on the local electric field E, one should also take into account the spectral shape of the resonances as well as the spatial position of SERS spectrum acquisition.