Hydrogen adsorption on a HfC(111) surface: angle-resolved photoemission study

Angle-resolved photoemission spectroscopy utilizing synchrotron radiation h as been used to study the adsorption of hydrogen on a HfC(111) surface. It is found that hydrogen adsorbs dissociatively on the HfC(111) surface formi ng a (1X1) overlayer at the saturation coverage. A H1s-induced bonding stat e which is split-off from the substrate valence band is found at 7.2 eV at the <(<Gamma>)over bar> point. In addition, another H-induced state is foun d at just below the Fermi level in off-normal-emission spectra, and the sta te is ascribed to an extrinsic surface state caused through the H-induced m odification of surface electronic states. (C) 2001 Elsevier Science B.V. Al l rights reserved.