Figure 3
Simulation results. (a) Maximum electric field intensity (|E/E0|2) enhancement at mid-gap between core and satellites as a function of SiO2 thickness w. (b) Spatial distribution of electric field intensity enhancement at 782 nm wavelength for only Si (w = 0, first column), w = 130 nm (second column), and only glass (third column). The substrate-air interface is depicted by a black line, and the figures depict (top) the xy-plane cut bisecting the nanogaps and (bottom) the xz-plane cut. (c) Collected far-field Raman scattering power fraction η (normalized, i.e., for one molecule) by the objective with NA = 0.75 and (d) theoretical (solid red line) and experimental (black star) SERS intensity at 997 cm−1 as a function of the silica thickness. The experimental SERS data for each sample is a mean value of measurements from five random spots. Note that the dash lines are simulated near field enhancement (purple) and far field interference enhancement (green) at 848 nm (997 cm−1) a function of the silica thickness (Eqn. 2).
