Influence of the dimension, geometry, and orientation of nanostructures on the distribution of the electric field in matters of enhancing of Raman scattering

The presented work reflects and analyzes the results of numerical simulation of the electric field strength dependence on the dimensionality and geometry of gold nanostructures as well as their orientation relative to the polarization of the incident radiation. The simulation of the electric field strength near a single nanostructure was performed using the Finite-Difference Time-Domain (FDTD) method. FDTD modeling is an effective theoretical way to study the interaction between electromagnetic waves and plasmonic nanoobjects represented by single gold nanorods with different geometry (cylinder, spherical cylinder, elongated ellipsoid) and variable half-length (L =10–120 nm). The radiation source was a plane-polarized wave (λ = 632 nm). As a result of the simulation, the localization of the electric field near the nanostructures has been determined and the maximum theoretical values of the near-field strength have been obtained. The dependence of the electric field strength maxima has been demonstrated to be nonlinear on the half-length of gold nanostructures in case of their longitudinal orientation to E-vector. The obtained theoretical calculations of the electric field strength near the plasmonic nanoparticles, including gold nanorods, allow us to determine the optimal nanoparticle parameters and excitation conditions for the plasmon resonance occurrence which in turn provides an opportunity to create SERS-structures with a high Raman scattering enhancement.