Figure 2

(a) FDTD simulation model of Au NPs/Al₂O₃/Au NPs and Au NPs/nanogap/Au NPs. FDTD simulated electric field distribution of (b) Au NPs/Al₂O₃(5 nm)/Au NPs and (c) Au NPs/nanogap(5 nm)/Au NPs. The excitation laser wavelength used in FDTD is 633 nm.