Plasmon excitations in graphitic carbon spheres

Abstract

Electron energy loss spectroscopy in a high-resolution transmission electron microscope has recently been used with success to characterize the electronic properties of closed cage nanometer-size graphitic particles. In the plasmon region, the experimental data reveal interesting size-dependent variations, which are not yet fully understood. The difficulties encountered in the interpretation of the spectra are principally due to the lack of a complete theoretical treatment of the anisotropic dielectric response in nanometer-size particles. In order to obtain a better understanding of the experimental data we propose a model based on nonrelativistic local dielectric response theory for electrons penetrating through a nested concentric-shell fullerene or the so-called ''carbon onion.'' The anisotropy of the electronic properties of the sphere is taken into account via the frequency-dependent dielectric tensor of graphite. The model can be applied to simulate electron energy loss spectra as well as line scans through energy filtered images and allows thus a direct comparison to experimental data. ͓S0163-1829͑98͒04724-9͔

Electronic structure and optical properties of concentric-shell fullerenes from electron-energy-loss spectroscopy in transmission

“…The energy position of these plasmons at 6 and 24 eV for a momentum transfer of 0.15 Å Ϫ1 confirms theoretical predictions that the -plasmon should occur in the energy range of 5-7 eV, and the ϩ plasmon at about 25 eV in the EELS spectra of isolated concentric carbon shells. 22,12 Furthermore, our results are in good agreement with those from previously reported spatially resolved transmission EELS data, which were taken on similar samples but with lower energy and momentum resolution using a transmission electron microscope.…”

“…A good agreement was observed, taking into account the anisotropy of the electronic properties via the frequency dependent dielectric tensor of graphite. 9,12 In this paper we present momentum-dependent EELS in transmission of concentric-shell fullerenes which have been produced by ion implantation and which have a uniform diameter distribution. These measurements are conducted in a purpose-built machine with a high-energy and -momentum resolution but with no spatial resolution, and are therefore complementary to the spatially resolved EELS measurements reported previously.…”

Characterization of carbon microspheres grown by HVPE

“…구의 크기나 형태 면에서 다양성에 따라 탄소 공 [1], 탄소 구 [2][3][4][5][6], 탄소 비즈 [7], 탄소 블랙 [8], 탄소 양파 [9][10][11][12][13] …”

Characterization of Nanophase Materials

“…Electron energy-loss is a continuous process, in which the electron is decelerated due to the attractive force F z ¼ (-e)E z owing to the field of the induced charges, resulting in energy-loss. The homogeneous medium theory has been extended recently for the cases of anisotropic dielectric medium, such as carbon onion structure and carbon nanotubes [48,49]. Shown in Figure 3.25a are a group of calculated EELS spectra for a carbon onion of radius 10 nm as a function of the electron impact parameter.…”