ON THE EXISTENCE OF MONOXIDES ON CLOSE-PACKED SURFACES OF LANTHANIDE METALS

Oxygen adsorption on Yb(lll) and Lu(0001) was studied by 4f and valenc e-band photoemission. For both systems, ordered surface oxides were fo und which are different from the well-known sesquioxides. They are cha racterized as monoxides that are not stable as bulk compounds. For Yb, such a surface oxide is only observed below room temperature where di ffusion of oxygen into the bulk is reduced. Lu monoxide is stable in t he presence of a localized d-like surface state which does not contrib ute to chemical bonding. In their electronic structure, these surface oxides resemble the lanthanide monosulfides which exist as bulk compou nds. (C) 1998 Elsevier Science B.V. All rights reserved.