The oxidation process of an HfC(1 0 0) surface has been investigated using photoemission spectroscopy utilizing synchrotron radiation. It is found that, when the HfC(1 0 0) surface is exposed to O-2 at room temperature, the C atoms of the surface region react with oxygen to form CO molecules and are desorbed from the substrate. The Hf atoms of the surface region are oxidized by stepwise reactions, and are finally oxidized to form an HfO2-like layer at high coverages (> 10 L). (c) 2004 Elsevier B.V. All rights reserved.