Tuning localized plasmon cavities for optimized surface-enhanced Raman scattering

Abstract

Mesostructured metallic substrates composed of square pyramidal pits are shown to confine localized plasmons. Plasmon frequency tuning is demonstrated using white light reflection spectroscopy with a wide range of structure dimensions from $400\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}3000\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. Using a simple plasmon cavity model, we demonstrate how the individual pit morphology and not their periodicity controls the resonance frequencies. By measuring the surface-enhanced Raman scattering (SERS) signals from monolayers of benzenethiol on the same range of mesostructures, we extract a quantitative connection between absorption, field enhancement, and SERS signals. The match between theory and experiment enables effective design of plasmon devices tailored for particular applications, such as optimizing SERS substrates.