Nano-scale metallic annular structures designed and simulation for surface-enhanced Raman scattering

摘要

Inducing a large electric field enhancement is very important to have good signals in surface-enhanced Raman scattering (SERS) experiments. In this study, the nano-scale sliver annular structures have been introduced to design the substrate for SERS experiment because of its localized surface plasmon (LSP) resonances phenomena. The excited electric field has been simulated by FDTD (finite-difference time-domain) and the design parameters, such as the thickness of the metallic film, the inner diameter, and the outer diameter, were changed. The largest electric field happens when the metallic film thickness is 5 nm and the inner and outer diameters are 0.1 μm and 0.4 μm, respectively. The results are in good agreement with the theoretical predictions. In addition, the dimer geometry of the annular structures has also been examined by FDTD to observe the field enhancement. The coupled plasmons effects appear obviously when two annular structures are very close. It indeed makes the excited electric field in the dimer structure larger than in the single one for 40 times. In conclusion, a design of dimer constituted with two annular structures which have 0.1 um and 0.4 um inner and outer diameters with 0 nm overlap owns the best electric field enhancement property and has great potential for SERS applications.