Structural study of the alkali-metal-induced (1 x 2) Ni(110) and c(2 x 4) Ni(110)/K/CO surface reconstructions.

Abstract

The adsorption of alkali metals on fcc(110) surfaces is known to induce (1\ifmmode\times\else\texttimes\fi{}n) n=2,3, . . . missing row (MR) reconstructions. We have used medium-energy ion scattering to study the structure of the (1\ifmmode\times\else\texttimes\fi{}2) Ni(110)/K and the c(2\ifmmode\times\else\texttimes\fi{}4) Ni(110)/K/CO surfaces. Our data for the (1\ifmmode\times\else\texttimes\fi{}2) reconstruction are consistent with a MR structure. This reconstruction has the interesting feature that the first-to-second-layer separation (${\mathit{d}}_{12}$) is expanded and not strongly contracted as has been observed for all other MR-reconstructed fcc(110) surfaces studied to date. For the c(2\ifmmode\times\else\texttimes\fi{}4) Ni(110)/K/CO system, the structural parameters are very similar to those for the (1\ifmmode\times\else\texttimes\fi{}2) system. Consequently, the c(2\ifmmode\times\else\texttimes\fi{}4) symmetry is due to CO ordering on top of a MR reconstructed substrate.