Plasmonic Properties of the Metal Nanoparticles (NPs) on a Metal Mirror Separated by an Ultrathin Oxide Layer

Abstract

The plasmonic resonance frequency of metal nanoparticles (NPs) strongly depend on the geometry, size, and separation between NPs. Here, a plasmonic structure is designed based on a film-coupled nanoparticle phenomenon and analytically investigated by a finite element method via COMSOL Multiphysics software tool. The optical behavior of the designed structure is studied and compared for two noble metals (gold and silver as a case study). Simulation results confirmed that structural elements such as dielectric layer thickness, metal film thickness, and metal nanoparticle separation distance significantly affect the plasmonic properties. Consequently, optimizing the dimensions of the mentioned structural elements results in a strong field enhancement in the dielectric gap layer. The simplicity of this structure, easy controlling of the dielectric gap layer thickness, strong field confinement in a limited area, and lack of incident light angle tunning are characteristic features of the proposed structure. Strong field enhancement in a limited volume makes this structure promising as plasmonic nanoantennas, SERS platforms, and sensing applications.