ELECTRON-ENERGY-LOSS SPECTROSCOPY STUDY OF THE ELECTRONIC-STRUCTURE OF A STABLE DECAGONAL QUASI-CRYSTAL AL70NI15CO15

Electron-energy-loss spectra of a stable decagonal quasicrystal Al70Ni 15Co15 have been obtained from single-quasicrystal areas of 180 nm dia meter. Excitation spectra Al L-shell electrons (L edge) show a sharp o nset (Fermi edge) but a small rise in intensity, indicating the presen ce of a pseudogap. The onset energy of Al L-edge spectra of the quasic rystal is higher than that of aluminium by 0.4eV, indicating an increa se in the covalent nature in the bonding of the quasicrystalline phase as shown earlier by Terauchi et al. The spectra of valence electron e xcitation exhibit a volume plasmon peak at 17.0eV with a full width at half-maximum (FWHM) value of 5.4eV. The width shows a stranger dampin g of the volume plasmon than those sp metals (FWHM, 0.4-1.5eV) and sp semiconductors (FWHM, 3-4eV). The origin of the strong damping is attr ibuted to interband transitions of the d electrons.