Plasmon excitations in graphitic carbon spheres measured by EELS

Abstract

The determination of the physical properties of individual nanometer-size particles has made rapid progress with the availability of local probe techniques during the past years. Electron energy-loss spectroscopy in a high-resolution transmission electron microscope is one experimental tool that can give insight into the intriguing properties of such small particles. The interpretation of the experimental data of the plasmon excitations is well established in the case of isotropic particles of different geometries. For the case of anisotropic particles such as multiwall fullerenes ͑carbon onions͒, the interpretation schemes had to be reviewed. In a recent publication, we have proposed a formalism based on nonrelativistic local dielectric response theory for high-energy transmission electron microscopy electrons penetrating or passing close by an anisotropic particle ͓Stöckli et al., Phys. Rev. B 57, 15599 ͑1998͔͒. Here we report a detailed comparison of experimental data with the excitation probabilities obtained within this formalism. We show that there is an excellent agreement between theory and experiment. In consequence, we are able to interpret the plasmon loss data of multiwall fullerenes and draw conclusions on their physical properties.

Spatially resolved measurements of plasmonic eigenstates in complex-shaped, asymmetric nanoparticles: gold nanostars

“…In the past decades, an important number of spatially resolved EELS studies in the low-loss region (where optical transitions are measured) have been performed; for a review, see, e.g., [18,19]. Most of these experimental and theoretical studies focused on the measurement of Interface Plasmons (IPs) and, to a smaller extent, to other boundary-related excitations for different geometries such as spheres [20], cylinders [21][22][23][24][25][26][27] and single or multi-layers [28][29][30][31]. However, they essentially considered both an energy range above 4 eV, i.e., the UV spectrum, and highly symmetric configurations.…”

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

“…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.…”

“…in agreement with the proposed structure. 8 The electronic properties of such carbon onions were characterized by spatially resolved electron energy-loss spectroscopy ͑EELS͒ in transmission 5,9,10 and by EELS in reflection. 11 From a comparison of the plasmon positions in transmission EELS and in reflection EELS at different geometries and electron beam energies, additional features were observed in the loss function, and were explained by tangential and radial surface plasmons.…”

Photoemission study of onionlike carbons produced by annealing nanodiamonds

“…2,[4][5][6][7] Carbon onions produced by electron irradiation of a carbon nanomaterial have a perfect spherical form and well ordered structure, but due to the small rate of production they can be studied only by high-resolution transmission electron microscopy ͑HRTEM͒ and electron energy loss spectroscopy ͑EELS͒. 8 De Heer and Ugarte 9 demonstrated the possibility of producing macroscopic quantities of onionlike carbon ͑OLC͒ consisting of hollow carbon onions with from 2 to 8 graphitic shells and with outer diameters ranging from 3 to 10 nm by heating carbon soot, produced by an arc-discharge method, in vacuum at 2100-2250°C. Raman spectra of this material revealed pronounced differences to other graphitic materials.…”