Systematic study of the size and spacing dependence of Ag nanoparticle enhanced fluorescence using electron-beam lithography

We study the enhancement of fluorescence by Ag nanopillars on a semiconducting substrate in which the pillar size, shape, and spacing is varied systematically using electron-beam lithography. Local maxima in the enhancement versus lateral size, as large as a factor of ∼20 are observed, and vary both with the shape of the pillars and the wavelength of the excitation. We find that the size, shape, and spacing dependence is in qualitative agreement with a model based upon resonant coupling with particle plasmon polaritons. We also find increased enhancement for particle shapes producing high local electric fields.