Structural analysis of the oxidized Cu bilayer on Ru(0001) by tensor LEED

A tensor LEED analysis confirms the previously proposed model of a modified Cu2O surface layer forming a (3 x 2 root3)-O/Cu structure on Ru(0 0 0 1). The hexagonal sandwich structure of Cu2O(1 1 1) is modified to wave-like O- Cu-O chains arranged along [1 1 2] directions. The oxidized surface layer e xhibits a Ru/Cu-O-O-Cu--O stacking containing half a monolayer of O. The at oms of the interface Cu plane continue the hcp stacking sequence of the Ru substrate, whereas those of the next Cu plane occupy fee lattice sites. Bot h Cu planes are buckled with a buckling amplitude of 0.26 Angstrom in each case and the glide-plane symmetry saved. This distortion within the oxidize d Cu film leads to a considerable variation of the O-Cu bond lengths compar ed to the ideal value of 1.85 Angstrom in Cu2O. whereas the spacings betwee n O layers and between center of mass planes of buckled Cu layers exhibit v alues typical for Cu2O. However, there is a considerable asymmetry of the O -Cu interlayer spacings involved. The best-lit Pendry R-factor (R-P = 0.45) appears to be acceptable in view of the complexity of the structure and of the restricted quality of the experimental conditions. (C) 2001 Elsevier S cience B.V. All rights reserved.