N. Pauly, S. Tougaard, F. Yubero
Physical Review B, 73 (2006) 035402 (1-11)
Development of models describing the processes undergone by an electron when it travels in the surface region of solids is of great importance to acquire a more complete understanding of electron spectroscopies as x-ray photoelectron spectroscopy, Auger electron spectroscopy, or reflection-electron-energy-loss spectroscopy. Based on their previous semiclassical dielectric response model, and Tougaard and Yubero [Surf. Interface Anal. 36, 824 (2004)] recently developed the software QUEELS (QUantitative analysis of Electron Energy Losses at Surfaces), which allows to easily perform electron energy loss calculations within a dielectric response theory for different cases of electrons moving near surfaces in general geometries. We present results obtained within this model for an incoming electron that is backscattered in the surface region. The separate interactions that take place while the electron moves in the vacuum and in the medium are also studied. We show that coupling effects between the incoming and outgoing trajectories occur with a magnitude that depends on the trajectory angle to the surface and on the backscattering depth. We find that this results in an oscillating behavior of the effective inelastic electron scattering. By studying the spatial and time dependence of this phenomenon, we can conclude that it originates from charge fluctuations of surface plasmons excited when the electron enters the solid. Moreover, we find that the main oscillatory behavior is damped and the characteristic damping energy is linearly correlated to the damping of the oscillator in the dielectric function and to the energy of the plasmon.