Electronic structure of the Zr suboxide layer formed on a ZrC(100) surface

Angle-resolved photoemission spectroscopy utilizing synchrotron radiation has been used to study the electronic structure of the ZrC(1 0 0) surface covered by a ZrO-like layer. When the ZrC(1 0 0) surface exposed to 50 L O-2 is heated at 950 degreesC, a ZrO-like layer is formed on the surface and the surface is activated towards gas adsorption. Angle-resolved photoemission measurements show that the O 2p-derived bands show clear dispersion along both the 10 O (MM) and <0 1 1> (GammaX) symmetry directions of ZrC(1 0 0). Since the surface gives a sharp (1 x 1) LEED pattern, it is concluded that a well ordered ZrO layer having a (1 x 1) periodicity is formed on the ZrC(1 0 0) surface. The O 2p-derived bands show no dispersion along the axis normal to the surface, thus the bands can be viewed as two-dimensional electronic states. In addition to the O 2p-derived bands, partially filled states are found around the Fermi level in the ZrO-like layer. The states are removed by water or oxygen adsorption. The origin of the states is discussed and the states are ascribed to partially filled Zr4d states. (C) 2002 Elsevier Science B.V. All rights reserved.