Electron energy loss spectroscopy investigation of volume and surface plasmons at the Al–Pd–Mn fivefold surface
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We have measured the electron energy losses on different Al–Pd–Mn quasicrystal surface states established by low energy electron diffraction, X-ray photoelectron spectroscopy and Auger electron spectroscopy. On the well characterized and ordered Al–Pd–Mn quasicrystalline surfaces, the energy loss signal with an energy of incident electrons at 2keV shows a strong peak at 16eV and a satellite at about 33eV. As the electron primary energy is decreased to 260eV, an energy loss at 10.5eV is clearly observed. A short ion bombardment (1μA at 500eV during 1min) erases this loss at 10.5eV which can be recovered by annealing at 800K. All these observations are simply attributed to the existence of a bulk plasmon at about 16eV and a surface plasmon at 10.5eV. The ratio between these two energies is 1.52. This is quite close to the expected √2 from the classical plasmon model. On the crystalline partially annealed surface, a bulk plasmon is observed at about 16.5eV. Oxygen-contaminated surface presents a bulk plasmon shifted towards higher energy of about 20eV.