Figure 5. FDTD simulation results of bimetallic nano-island models.

(a), Three-dimensional model of the nano-island structure. (b), Cross-sectional and planar views of the calculated radial EM field components of the multilayer nano-island structure with parameters D₁ = 30 nm, D₂ = 25 nm, D₃ = 20 nm, d₁ = 25 nm, d₂ = 20 nm, d₃ = 15 nm, h₁ = 40 nm, h₂ = 35 nm, and h₃ = 30 nm. Height of the spherical cap is 5 nm and space between two particles is 10 nm. The inset in (b) shows the k-vector and polarization of the incident light. The 5-fold enhancement in the EM field is only artificially set to provide better intuitive models. (c), Calculated electric field intensity of a single metal aluminum model (I) and silver model (II). (d), Calculated electric field intensity of (III) Al-Ag-Al, (IV) Al-Ag-Ag models with fixed parameters in (b), and (V) Al-Ag-Ag with D₂ = 30 nm, d₂ = 20 nm with other parameters being fixed.