Surface oxidation of an AlPdMn quasicrystal, characterized by X-ray photoelectron spectroscopy

Abstract X-ray photoelectron spectroscopy (XPS) is used to determine the extent of oxidation of each of the three metals which comprise a quasicrystalline alloy. A single-grain sample, oriented with the fivefold axis perpendicular to the surface plane, and with nominal bulk composition Al 70 Pd 21 Mn 9 is used. The oxide which results from exposure to ambient gas at room temperature is compared with that which results from exposure to pure oxygen in ultrahigh vacuum at temperatures up to 870 K. XPS probes the near-surface region (ca. top 100 A), and shows that only the Al can be oxidized. The depth of the oxide layer depends systematically upon the conditions of treatment, but is always very thin — in the range of about 5–30 A. Taken together, the data suggest that the surface forms a thin, passivating, surface layer of aluminum oxide.