Electron-energy-loss spectroscopy study of the electronic structure of a stable decagonal quasicrystal Al70Ni15Co15

Electron-energy-loss spectra of a stable decagonal quasicrystal Al70Ni15Co15 have been obtained from single-quasicrystal areas of 180 nm diameter. Excitation spectra Al L-shell electrons (L edge) show a sharp onset (Fermi edge) but a small rise in intensity, indicating the presence of a pseudogap. The onset energy of Al L-edge spectra of the quasicrystal is higher than that of aluminium by 0.4 eV, indicating an increase in the covalent nature in the bonding of the quasicrystalline phase as shown earlier by Terauchi et al. The spectra of valence electron excitation exhibit a volume plasmon peak at 17.0 eV with a full width at half-maximum (FWHM) value of 5.4 eV. The width shows a stronger damping of the volume plasmon than those sp metals (FWHM, 0.4- 1.5 eV) and sp semiconductors (FWHM, 3-4 eV). The origin of the strong damping is attributed to interband transitions of the d electrons.