Reconstruction of the oxygen-covered Cu{110} surface identified with low energy Ne + and H 2O + ion scattering

Abstract

The structure of the oxygen-covered Cu{110} surface was investigated using low energy (keV region) Ne + and H 2O + bombardment. This involved measuring photograms and ϑ-ψ diagrams of scattered Ne + and O − ions and of positively and negatively charged oxygen recoil ions. The adsorbate-induced structure was studied by the methods described in our earlier papers. The oxygen covered surface was found to be reconstructed. The reconstruction can be described by the “missing row” model, in which all 〈100〉 atom rows adjacent to the oxygen-containing 〈100〉 rows have disappeared from the surface. The lateral position of chemisorbed oxygen atoms is found in the bridge position in the 〈100〉 surface row. The Cu atoms in the oxygen-containing surface rows are in the same positions as they were on the clean surface. This reconstruction can explain the (2 × 1) LEED pattern observed for oxygen-covered surfaces, since the unit cell in the reconstructed surface is twice as large as the unit cell of the clean surface. The maximum coverage degree for exposures up to 100 L is found to be one oxygen atom per unit cell of the reconstructed surface. From the differences between the photograms of O − and of O + recoil ions it is deduced that there may be a second kind of adsorption site in the first two surface layers where oxygen can become chemisorbed. It is suggested that this site is near the second layer, below the position of the missing row in the surface.