Fig. 1. Schematic diagram and SEM images of fabricating composite structure. (a) Schematic diagram of fabricating AAO-AgNPs composite structure; (b) SEM image of AAO mask; (c) (d) SEM images of AAO-AgNPs composite structure; (e) size distribution of Ag nanoparticles; (f) statistical results of gap size

Fig. 2. SERS sensitivity test results. (a) SERS spectrum of R6G molecules with different concentrations on AAO-AgNPs composite structure; (b) SERS spectrum of 10^-16 mol/L R6G molecular on AAO-AgNPs composite structure; (c) SERS spectrum of R6G molecules on different composite structures; (d) scatter diagram of relationship between Raman spectral intensity and lg C (C is R6G concentration) at 611 cm^-1

Fig. 3. Results of sample uniformity, stability test, and actual molecular detection. (a) Plot of Raman mapping for AAO-AgNPs composite structure; (b) intensity distribution of peaks; (c) time stability test; (d) scatter diagram of relationship between intensity and time at 611 cm^-1; (e) multi-molecule detection result; (f) R_SD obtained by 10^-8 mol/L thiram detection

Fig. 4. Results of FDTD electric field simulation. (a) SiO₂-AgNPs simulation model; (b) x-y plane electric field intensity distribution of SiO₂-AgNPs; (c) x-z plane electric field intensity distribution of SiO₂-AgNPs; (d) AAO-AgNPs simulation model; (e) electric field intensity distribution of AAO-AgNPs at x-y plane (30 nm AgNP); electric field intensity distributions of AAO-AgNPs at x-z plane for (f) 30 nm AgNP, (g) 34 nm AgNP, (h) 36 nm AgNP, and (i) 40 nm AgNP; (j) electric field intensity distribution at x-z plane for silver aggregation distribution