Angle-resolved photoemission study of the hydrogen-adsorbed Cr(110) surface at 80 K

The electronic state of the hydrogen-adsorbed Cr(110) surface at 80 K has been investigated using angle-resolved photoemission spectroscopy. We observed a p(2\ifmmode\times\else\texttimes\fi{}2) low-energy electron-diffraction pattern at \ensuremath{\sim}2 L, and a ``streaked'' (1\ifmmode\times\else\texttimes\fi{}1) pattern along the [11\ifmmode\bar\else\textasciimacron\fi{}0] azimuth at above 10 L. The photoemission results show that for the p(2\ifmmode\times\else\texttimes\fi{}2) phase an H 1s--derived state, having a nearly constant binding energy of \ensuremath{\sim}5.5 eV below the Fermi level, is observed in the outer part of the surface Brillouin zone, that is, outside the Cr s-p band projections. [Here 1 langmuir (L)\ensuremath{\equiv}${10}^{\mathrm{\ensuremath{-}}6}$ Torr sec.] On the other hand, for the streaked (1\ifmmode\times\else\texttimes\fi{}1) phase, an H 1s--derived state, split off from the Cr bulk bands, is found at the binding energy of 7.8 eV at \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} and shows considerable dispersion of \ensuremath{\sim}2.8 eV in the [001] azimuth being consistent with the periodicity of the substrate structure. In addition, a H-induced surface state is found at 2.5 eV at \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} for both phases. The nature of the Cr-H chemisorption bond is discussed.