Photoelectron spectroscopy of some 3d and 4f oxides exposed to Ar+ beams

The effects of the ion bombardment on the surface electronic structures and electrical properties of transition-metal oxides and lanthanide oxides have been investigated by a photoelectron spectroscopy and measurement of surface electric conductivity. Many of the oxides (TiO2, CeO2, etc.) are reduced to the oxides in lower valence states by the 8-keV Ar+-ion bombardment, but there exist some oxides (Sc2O3, La2O3, etc.) which are stable against the bombardment. For TiO2, the bombardment-induced reduction brings about Ti3d-derived new band at the Fermi level, together with the increase of the surface electric conductivity. The mechanism leading to bombardment-induced surface electric conductivity is discussed in relation to the surface electronic structures. (author)