Atomic structure of the SbCu surface alloy: a surface X-ray diffraction study

The dissolution at 400 degrees C of an antimony layer deposited at room tem perature on a Cu(111) substrate leads to a surface alloy with a p(root 3x r oot 3)R 30 degrees x 30 degrees superstructure and a Sb composition of 1/3. We present here a structural study of this Sb-Cu compound by surface X-ray diffraction (SXRD). The best agreement is obtained for a Cu,Sb surface laye r with Sb atoms substituting 1/3 of the Cu atoms, over an essentially unper turbed Cu(111) plane. The largest relaxation is undergone by the Sb atoms w hich rise by 0.32+0.02 Angstrom over the mean plane of its Cu neighbours. N o substantial in-plane relaxations were observed. (C) 1999 Elsevier Science B.V. All rights reserved.