Oxygen on Cu(100) surface structure studied by scanning tunneling microscopy and by low-energy-electron-diffraction multiple-scattering calculations

A scanning-tunneling-microscopy study for a surface formed by the chemisorption of oxygen on Cu(100) and displaying a (2 {}2 ×{} {}2 )R45^∘{} low-energy-electron-diffraction (LEED) pattern shows the expected rotationally related domains but no unambiguous evidence for coexisting regions of c(2×{}2) symmetry. There is a clear pairing of atomic rows, but a low corrugation ({}0.2 {}). These features are consistent with results from a new LEED multiple-scattering analysis applied to six diffracted beams for normal incidence. The missing-row model recently proposed [Zeng et al., Surf. Sci. 208, L7 (1989)] is extended to include a 0.30-{} lateral relaxation for top-layer copper atoms adjacent to the missing rows, and small (around 0.10-{}) vertical relaxations in both the first and second copper layers. These features yield the best correspondence between experimental and calculated LEED intensities yet reached for this surface structure.