Geometrical Effects on Electromagnetic Enhancement to SERS from Metal Nanoparticle Dimer Arrays

Much recent effort has been devoted to the study of the optical properties of metal nanoparticle substrates. In such finely ordered structures, surface plasmons can be induced by incident light. These collective excitations of the electrons in the nanoparticle create localized areas of high electromagnetic field intensity. The intense local fields generated are of interest for various applications, including Surface-enhanced Raman Scattering (SERS) for molecular detection and sensing. In this thesis, the optical properties of various nanoparticle dimer and array geometries are considered, including gold triangular prism dimers and silver spherical dimers. The effect of SERS due to electromagnetic interaction of the metal nanoparticles with incident light is computed using the finite-difference time-domain (FDTD) method. These results are compared with those from generalized Mie theory simulations and recent experimental work. The positions, wavelengths, and magnitudes of maximum electric field enhancement for different geometries are presented. These findings may serve as important guidance in future design of nanoplasmonic devices.