Electronic structure and nature of the bonding at the Cu(110)+c(2×2)-Si surface alloy

The electronic structure of the Cu(110)+c(2×2)-Si surface alloy has been studied experimentally by synchrotron radiation photoemission spectroscopy. We have recorded normal emission photoemission spectra as a function of the photon energy, Si coverage and angle of incidence of the polarized light in order to identify the electronic features induced in the Cu valence band by the presence at the surface of an ordered Si–Cu bidimensional layer. Two main dispersionless bands in the direction perpendicular to the surface and centered around −3 and −1 eV of binding energy are the most characteristic electronic features of the system. Most of the details in the photoemission spectra are well reproduced by a local density of states calculation employing the Extended Hückel Theory. These results suggest that the electronic states from the surface alloy are mainly originated by an in-plane hybridization of the Cu 3d electrons from the outermost layer with the Si 3p electrons.