A HE-SCATTERING STUDY OF THE HYDROGEN-INDUCED STREAKY PHASE OF NI(110)

The structure of the (1 x 2) ''streaky phase'' formed upon adsorption of deuterium on Ni(110) was studied using He scattering. The presence of a pronounced rainbow pattern in the in-plane-spectra observed with the beam incident along [001] signals unambiguously that the ''streaky phase'' is of the missing-row structure type. The corrugation of the (I X 2) troughs could be determined as approximately 1.55 angstrom, which represents an increase of approximately 0.3 angstrom with respect to the estimated corrugation of a clean Ni-missing-row surface; this observation suggests that the deuterium atoms occupy sites near the ridges of the missing-row troughs. From out-of-plane measurements of the remnant (2 x 1) phase, the fraction of unreconstructed Ni domains coexisting with the missing-row structure has been estimated as 10%.