SYMMETRY PROPERTIES OF THE ERSI(1.7)-VALENCE BAND STATES

The electronic structure of epitaxial erbium disilicide grown on Si(11 1) has been studied with angle-resolved photoemission. Important chang es in the photoelectron spectra are observed as a function of the sili cide film thickness. The symmetries of the valence band features are d etermined by varying the light polarization and using dipole selection rules. It is found that the surface state located at 1.80 eV below E( F) has Lambda(3) symmetry and consequently derives from p(xy)-like sta tes. The structures depending on the silicide film thickness and locat ed in the 0.60-1.30 eV and in the 2.50-4.00 eV binding energy ranges d isplay Lambda(1) symmetry. They are attributed to p(z)-like states ori ginating from the silicide Si graphitic planes. Our results are consis tent with the expected electronic structure in terms of pi and sigma S i3p derived states. In particular the electron states at similar to 1. 00 eV binding energy are pi states induced by the presence of an order ed array of Si vacancies in the silicide Si graphitic planes, rather t han sigma states reflecting directly the dangling bonds related to the se vacancies.