Hydrogen-induced reconstruction of the W(100) surface, studied by surface core level spectroscopy

We report W(4f{hook}) surface core level shifts which yield new information on the energetics of the W(100) (1 × 1) → C(2 × 2)H phase transition. At small hydrogen coverages we find two co-existing surface core levels from atoms on normal lattice sites and from atoms in reconstructed domains. These surface levels are shifted to smaller binding energy (toward EF) by 0.35 eV and 0.13 eV relative to the bulk level, respectively. The most stable configuration is obtained at a fractional coverage θH ≅ 0.2, at which all surface atoms are shown to be paired with neighboring atoms in the surface plane. © 1981.