Dielectric response theory for electron energy loss in clad cylindrical systems

Abstract

Inelastic interactions between an electron and a clad cylindrical system were investigated using the dielectric response theory. By solving the Poisson equation and applying the boundary conditions, these interactions were formulated in terms of the surface, interface and volume excitations. Formulas of the differential inverse inelastic mean free path ͑DIIMFP͒ were derived for electrons moving parallel to the axis of such a cylindrical structure. A sum-rule-constrained extended Drude dielectric function with spatial dispersion was applied to the calculations of the DIIMFP for a Si cylindrical tube or a Si cylinder clad in a SiO 2 film. For the Si tube, it was found that surface excitations occurred as electrons moved near either the inner or outer surface of the tube and either inside or outside Si. Whereas, volume excitations arose only for electrons moving inside Si. Surface excitations increased, or volume excitations decreased, as electrons moved closer to the surface. For the Si cylinder clad in the SiO 2 film, inelastic interactions were contributed from volume, surface, and interface excitations. Calculated results showed that the relative importance of these excitations depended on the electron distance from the surface or interface of the cylindrical system, the radius of the Si cylinder, and the thickness of the SiO 2 film.

Role of spatial dispersion in defining the image of a point charge near the dielectric surface

“…At increasing m the distance between the left and right roots diminishes but always to be nonzero. The same two surface-mode result was obtained in a series of papers (see, e.g., [1][2][3][4][5][6]). Our result that the volume eigenfrequencies are not arisen in the case of cylindrical tube, when the external charge moves in vacuum near the dielectric, apparently, founds in the agreement with the analogous conclusion in the work [5].…”

“…Some important electromagnetic properties of such a specimen were described in the work [5]. In this case (see the cross section in Fig.…”

“…Usually, in classical electrodynamics (see, e.g. [1][2][3][4][5][6]), this problem is solved without taking into account the spatial dispersion of solid polarization properties near the surface. In this paper we investigate the corrections to be done if the medium obey spatial dispersion.…”

Calculation of the energy losses of charged particles upon motion near a nanotube within dielectric formalism

“…In the present work a carbon nanotube has been simulated by using a cylindrical layer with a given dielectric function, taking into account the temporal dispersion of the medium. This approach was also used in [3][4][5], where the energy losses were calculated and the polarization potential of charged particles upon motion parallel to the symmetry axis of a continuous cylinder or cylindrical layer was obtained. Another approach using the hydrodynamic model for an elec tron liquid [1,6] gives similar results [7].…”

Nonlocal effects in the plasmons of nanowires and nanocavities excited by fast electron beams

“…Dispersive effects in cylindrical nanostructures have been also studied by other authors in terms of the band structure of the cylinder. 50,73,74 An attempt to extend the existing classical dielectric approach has been made 75 by partially considering momentum transfer along the wire axis but not considering momentum transfer perpendicular to the wire, therefore missing the effects related to the electron density correlation. More sophisticated methods based on a selfconsistent solution of the electronic density within the timedependent density-functional theory ͑TDDFT͒ can give full account of nonlocal effects in the response.…”