Predicted energy-loss spectrum of low-dimensional plasmons in a metallic strip monolayer on a semiconductor surface

In view of high-resolution electron-energy-loss spectroscopy, we predict the energy-loss spectrum of low-dimensional (LD) plasmons in a metallic strip monolayer on a semiconductor surface. By means of the time-dependent local density approximation, we calculate the dynamical response of our electron system to some typical trajectories of a probe electron incident on the surface along the strip. As shown in our previous work, the energy dispersion of the LD plasmons is composed of a series of dispersion branches where the node number in oscillation of the induced electron density across the strip increases one by one with ascending energy. These branches can produce a series of loss peaks in the spectrum. The branch of the two-node modes gives rise to an outstanding loss peak, and the branches of the zero-node modes (symmetric edge plasmons) and the four-node modes also create significant loss peaks, when the intersection of the scattering plane with the surface plane runs around the center line of the strip region. The branch of the one-node modes (antisymmetric edge plasmons) yields a remarkable loss peak, when the intersection runs just near one of the strip edges. These loss peaks should actually be observed in the spectrum, if there are a sufficient number of strip regions in a surface area illuminated by an electron beam.