Mapping localized plasmon modes in metal nanoparticles via electron energy loss spectroscopy and cathodoluminescence

In this work, the rich structure of SP modes localized in individual noble-metal nanoparticles prepared via lithography or colloidal chemistry is explored by optical spectroscopy, spatially resolved electron energy-loss spectroscopy (EELS) performed in a scanning transmission electron microscope (STEM), and by electron beam-induced radiation emission performed in a scanning electron microscope. Spectral features and spatially-resolved maps of SP modes collected for individual nanoparticles of different morphologies (rods, decahedra, prisms, and split-ring resonators) are shown to be in good agreement with theoretical STEM-EELS and optical excitation calculations obtained using the boundary element method based upon rigorous solution of Maxwell's equations.