Efficient Generation of Propagating Plasmons by Electron Beams

We report highly efficient generation of propagating plasmons by electron beams in planar films, planar dielectric cavities, metallic wires, and nanoparticle waveguides. Electron-induced plasmon excitation is investigated in (1) gold thin films, both free-standing or supported on a silica substrate, (2) gold-silica-gold planar cavities, (3) gold nanowires, and (4) gold nanoparticle arrays. We obtain excitation yields as high as 10(-2) plasmons per incoming electron over the visible and near-infrared range. Symmetric and antisymmetric plasmon modes are found to be more easily excited in thick and thin films, respectively, and in particular leaky plasmons in supported films are shown to be excited with very large probability exceeding one plasmon per electron. Generation of guided plasmons in metallic particle arrays is also proved to be attainable by aiming the electron at one end of the waveguide. The temporal evolution and spectral distribution of excited plasmons are discussed as well. Our results provide full support for the application of electron bombardment to excite propagating plasmons with high efficiency, thus solving the standing problem of plasmon generation at designated locations.