OXYGEN INDUCED ADDED-ROW RECONSTRUCTION OF THE NI(110) SURFACE

The oxygen induced reconstructed phases of the Ni{110} surface have been studied by time-of-flight scattering and recoiling spectrometry (TOF-SARS). The substrate structures are determined from experimental measurements of azimuthal angle (delta) and polar incident angle (alpha) anisotropies in the scattered Ne intensities coupled with classical trajectory simulations for shadow cone analysis. By monitoring features in the TOF-SARS scans that are unique to specific phases, it is possible to follow the migration of the first-layer Ni atoms as a function of O2 exposure. The results show that upon increasing exposures of the clean Ni(110}-(1 X 1) surface to O2, a series of LEED patterns [initial p(3 X 1), p(2 X 1), and final p(3 X 1)] is produced corresponding to three surface phases which differ only in the density of the first-layer Ni [001] rows. These nascent "added rows" are stabilized by bonding to oxygen atoms which reside in the long-bridge positions along the [001] rows. Structural models for the three phases are confirmed from the TOF-SARS data and the inhibiting effects of carbon and sulfur impurities on the reconstruction is considered.