Figure 2.

Plasmonic breathing mode dispersion of silver nanodisks. (a) Experimental EEL spectra measured in the center of 30 nm thick silver discs with diameters between 130 to 1000 nm, as depicted in the electron microscope images to the right. The spectra were smoothed by averaging EEL counts over an energy-width of 0.1 eV. The dashed lines follow the spectral position of three breathing modes. (b) Dispersion relation of the breathing modes including data from 13 disks with diameters from 50 to 2200 nm. The loss energy is derived from the measured peak energies, the wavenumber k is obtained from the particle diameter d via k = 2nπ/d (n = 1, 2, 3). The line plots the calculated surface plasmon dispersion at the silver/silicon nitride interface of a 30 nm silver/30 nm silicon nitride multilayer.