BISMUTH ON COPPER(110) - ANALYSIS OF THE C(2X2) AND P(4X1) STRUCTURESBY SURFACE X-RAY-DIFFRACTION

Surface X-ray diffraction has been used to analyze the atomic structur es of the Cu(110)-c(2 x 2)-Bi and Cu(110)-p(4 x 1)-Bi reconstructions with submonolayer coverages. A quasi-hexagonal c(2 x 2) adlayer struct ure is formed when half a monolayer of bismuth is deposited; the cover age corresponds to 1.08 x 10(-15) atoms cm(-2). There is one Bi atom p er c(2 x 2) surface unit cell, and the nearest-neighbor distance on th e planar overlayer was found to be 4.43 Angstrom. In the case of the p (4 x 1) reconstruction formed at a coverage of 0.75 monolayers, both t he in-plane and out-of-plane data are in excellent agreement with a mo del in which every fourth Cu row in the [001] direction of the topmost layer is replaced by Bi atoms to form a substitutional surface alloy. (C) 1997 Elsevier Science B.V.