Enhancement of Raman scattering by field superposition of rough submicrometer silver particles

Wavelength-dependent surface-enhanced Raman spectra of methylene blue adsorbed on rough submicrometer silver particles were measured. Results revealed a high enhancement factor (10(5)similar to 10(7)), especially in the long-wavelength region. Investigation on the far- and near-field optical properties of the particles showed a remarkably enhanced dipole plasmon resonance due to the presence of a rough particle surface. Through analyzing the plasmon resonance modes and the superposition of radiation fields, we found that the rough surface-induced field superposition results in the redistribution of optical fields around the particle, which becomes a key factor responsible for the high enhancement effect of metal particles. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4705083]