Angle-resolved photoemission study of the clean and oxygen covered ZrC(111) surface

Angle-resolved photoemission spectroscopy utilizing synchrotron radiation has been used to study the electronic structure of a ZrC(111) clean surface and the surface covered with oxygen. The spectra of the clean surface show a sharp peak at just below the Fermi lever, and the peak is ascribed to the emission from a surface state formed through a charge redistribution around the surface. The polarization dependent measurements show that the surface state is derived from the 4d(x2) orbital of the surface Zr atom at the <(Gamma)over bar> point. Oxygen adsorbs dissociatively forming a (1x1) overlayer at the saturation coverage. As the surface is covered with oxygen, the peak from the surface state is quenched and O 2p(z) and 2p(x,y) induced bonding states are formed at 5.3 and 6.0 eV, respectively, at the <(Gamma)over bar> point. The two-dimensional band structure of the O 2p induced states suggests that the O 2p(x),2p(y) and 2p(z) states should have nearly the same contribution to the chemisorption bonding on the ZrC(111) surface.