Effects of the Substrate Refractive Index, the Exciting Light Propagation Direction, and the Relative Cube Orientation on the Plasmonic Coupling Behavior of Two Silver Nanocubes at Different Separations

Abstract

In this paper, we presented a detailed theoretical investigation on the effects of changing the refractive index of the substrate and the interparticle separation distance on the electromagnetic field distribution around the face-to-face (FF) and the edge-to-edge (EE) oriented silver nanocube (Ag NC) dimers. We found that the contribution of the scattering to the absorption components is markedly decreased with increasing the substrate refractive index. This suggests that for surface-enhanced Raman spectroscopic (SERS) applications, the use of a substrate of very low refractive index is highly recommended. However, for photothermal applications, the use of substrate of high refractive index is recommended. Furthermore, we found that the wavelengths corresponding to the dipolar and multipolar modes are nearly unaffected by increasing the interparticle separation distances above 40 nm on the high refractive index substrate. However, on the low refractive index substrate, the dipolar peaks consistently red-s...