Correlative electron energy loss spectroscopy and cathodoluminescence spectroscopy on three-dimensional plasmonic split ring resonators

We present the surface plasmon resonance modes in three-dimensional (3D) upright split ring resonators (SRR) as studied by correlative cathodoluminescence (CL) spectroscopy in a scanning electron microscope (SEM) and electron energy loss spectroscopy (EELS) in a transmission electron microscope. We discuss the challenges inherent in studying the plasmon modes of a 3D nanostructure and how meeting these challenges benefits from the complementary use of EELS and SEM-CL. With the use of EELS, we detect a strong first order mode in the SRR; with comparison to simulations, we are able to identify this as the well-known magnetic dipole moment of the SRR. Combining the EELS spectra with SEM-CL on the same structure reveals the higher order modes present in this 3D nanostructure, which we link to the coupling and hybridization of rim modes present in the two upright hollow pillars of the split ring.