Image dipoles approach to the local field enhancement in nanostructured Ag-Au hybrid devices

TL;DR

This paper investigates how nanostructured silver and hybrid silver-gold devices enhance local electromagnetic fields using an image dipole approach, relevant for improving surface-enhanced Raman spectroscopy.

Contribution

It introduces an image dipole method to analyze surface morphology effects on field enhancement in nanostructured plasmonic devices, comparing silver and hybrid silver-gold systems.

Findings

Hybrid devices exhibit higher field enhancement due to localized surface plasmon states.

Surface defects and symmetry breaking significantly influence enhancement levels.

Results align with recent experimental observations.

Abstract

We have investigated the plasmonic enhancement of the radiation field at various nanostructured multilayer devices, that may be applied in surface enhanced Raman spectroscopy. We apply an image dipole method to describe the effect of surface morphology on the field enhancement in a quasistatic limit. In particular, we compare the performance of a nanostructured silver surface and a layered silver-gold hybrid device. It is found that localized surface plasmon states (LSP) provide a high field enhancement in silver-gold hybrid devices, where symmetry breaking due to surface-defects is a supporting factor. These results are compared to those obtained for multi-shell nanoparticles of spherical symmetry. Calculated enhancement factors are discussed on the background of recent experimental data.