Structure of N-2 adlayers on the highly corrugated Cu(110)-(2x1)O surface

The adsorption and structure of molecular nitrogen on the reconstructed Cu( 110)-(2 x 1)O surface has been studied by He-diffraction and temperature pr ogrammed desorption. Owing to the "added row" reconstruction, the Cu(110)-( 2 x 1)O surface exhibits a large corrugation along the [1 (1) over bar 0] d irection, i.e. perpendicular to the Cu-O rows. This has a marked influence on the adsorption properties and structure compared with the bare Cu(110) s urface. The N-2 molecules initially adsorb in a lattice gas phase which is stable up to rather high density. In this phase the desorption proceeds via first-order desorption kinetics. With increasing coverage the lattice gas eventually condenses into a (4 x 3) commensurate phase where the molecules are much more weakly bound. Potential calculations corroborate the existenc e of a low density phase in which the N-2 molecules adsorb along the trough s between Cu-O added rows with only negligible lateral interactions. The (4 x 3) phase is found to contain up to eight N-2 molecules per unit cell, ha lf of which occupy sites on top of the Cu-O added rows. A possible novel de sorption channel involving a metastable bi-molecular precursor is proposed that could provide a consistent explanation of the N-2 desorption data. (C) 1999 Elsevier Science B.V. All rights reserved.