chemisorption;
copper;
epitaxy;
low energy electron diffraction;
oxidation;
oxygen;
ruthenium;
scanning tunneling microscopy;
surface structure;
D O I:
10.1016/S0039-6028(97)00918-7
中图分类号:
O64 [物理化学(理论化学)、化学物理学];
学科分类号:
070304 ;
081704 ;
摘要:
The crystallographic aspects of O-induced structures on strained Cu films grown epitaxially on Ru(0001) are studied by scanning tunneling microscopy and high-resolution low-energy electron diffraction. O adsorption at 520 R removes the thickness-dependent relaxation structures of the O-free Cu film. Instead. structures appear corresponding to a film thickness reduced by one monolayer, accompanied with the formation of a O/Cu surface layer. Wave-like O-Cu-O chains along the [(1) over bar 12] direction are formed on the pseudomorphic Cu monolayer. The O/Cu structures on uniaxially reconstructed Cu bilayers depend on both the local stacking sequence and the extension of the unit cell. On moire-like Cu films (thickness > 3 ML), an O/Cu structure of well-established long-range order only occurs if O is preadsorbed on Ru(0001). The results obtained allow one to conclude that Cu-O segments (links) of the O-Cu-O chains should be regarded as surfactants for the O-mediated growth of Cu/Ru(0001). All O/Cu structures can be interpreted on the basis of O-Cu-O strings, in close relation to Cu2O/(111). (C) 1998 Elsevier Science B.V. All rights reserved.