Surface oxidation of the icosahedral Ag-In-Yb quasicrystal

Abstract

The oxidation of the high-symmetry surfaces of a single grain icosahedral $(i)$ Ag-In-Yb quasicrystal has been studied using x-ray photoemission spectroscopy. The oxidation was carried out in vacuum, air, and water. It is found that air exposure results in the same degree of oxidation as exposure to oxygen in vacuum. The oxidation in water is more effective. Among the three constituent elements, the core levels of Yb are most affected by oxidation, Ag core levels are unchanged, and In shows moderate effects as expected from heats of formation of bulk oxides of the three elements. The comparison of the results with pure elements also reveals that the oxidation of Ag, In, and Yb in the quasicrystal is very similar to that of pure elements in all three environments. Scanning tunneling microscopy and low-energy electron diffraction reveal that oxidation destroys the quasicrystalline order of the clean surface.