Structure of Cu(115): Clean surface and its oxygen-induced facets

Cu(001) vicinal surfaces facet when exposed to O. We have studied this process on Cu(115), which transforms from a clean surface to {104} and {113} facets, using surface x-ray diffraction. The Cu(115) surface exhibits a complex interlayer relaxation accounted for by basic elasticity theory; the vertical displacements of the three surface atoms an found to correlate with those of the subsurface atoms directly below. The O/Cu(104) facets do not, as previously proposed, involve any missing Cu rows, but the top three rows are expanded away from the bulk; the Cu-O chains which stabilize this surface are similar to those present on other O on Cu reconstructions. The O/Cu(113)(3 x 1) facets are significantly disordered, with stripes about 8 Angstrom wide running parallel to the atomic steps.