Low-energy electron diffraction study of oxygen-induced reconstructions on Cu(210)

The oxygen-induced reconstructions on Cu(210) have been investigated by low-energy electron diffraction (LEED). The adsorption of oxygen on Cu(210) leads to a series of (nx1) (n=2,3) reconstructions comprising Cu-O chains along the [001] direction on the topmost layer. The Cu(210)-(2x1)O structure is found to be the most thermodynamically favorable phase. A quantitative LEED analysis, performed by comparing the simulation results of different 2x1 and 3x1 models, confirms an added row model with oxygen sitting on the long bridge sites along the [001] direction. The oxygen atoms sit in a deeper position from the surface than the topmost Cu atoms, and the Cu-O rows relax upward. In the Cu(210)-(3x1)O structure with an oxygen coverage of 2/3 ML, oxygen atoms reside deeper than the accompanying Cu atoms in one Cu-O row, while in the adjacent row, oxygen sits higher than the Cu atoms. The nearest and second nearest neighbor Cu-O distances are determined to be 1.82+/-0.03 and 1.96+/-0.06 A respectively for both 2x1 and 3x1 reconstructions. The formation of relatively strong Cu-O bonds appears to be the driving force for both reconstructions.