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 square-root 2 X square-root 2)R 45-degrees low-energy-electron-diffraction (LEED) pattern shows the expected rotationally related domains but no unambiguous evidence for coexisting regions of c (2X2) symmetry. There is a clear pairing of atomic rows, but a low corrugation (less-than-or-similar-to 0.2 angstrom). 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-angstrom lateral relaxation for top-layer copper atoms adjacent to the missing rows, and small (around 0.10-angstrom) 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.