A scanning tunneling microscopy study of surface segregation of Sb at a Cu(111) surface

Surface segregation of Sb from the bulk of a Cu-0.45 at.% Sb single-crystal , annealed in situ at 400 degrees C, is studied in the (111) surface plane, employing an ultrahigh vacuum scanning tunneling microscope (STM). The STM images demonstrate that Sb atoms segregate substitutionally and do not exi st as adatoms at the (111) surface. Furthermore, the STM images reveals tha t the six Cu atoms surrounding each Sb atom, in the (111) plane, are signif icantly perturbed in terms of either electronic density or their atomic pos itions. The Cu atoms appear to be vertically and laterally displaced from t heir expected positions, thereby leading to an unexpected broken surface sy mmetry in the STM images. (C) 2000 Elsevier Science B.V. All rights reserve d.