SPIN-RESOLVED PHOTOEMISSION FROM SUBMONOLAYER AG ON SI(111) - AG ADSORPTION IN THE (SQUARE-ROOT-3XSQUARE-ROOT-3)R30-DEGREES PHASE WITH NO AG-AG INTERACTION AND IN THE 1X1 STRUCTURE WITH STRONG AG-AG INTERACTION

Ag/Si(111) has been studied by spin-, angle-, and energy-resolved photoemission with circularly polarized radiation from the Berliner Elektronenspeicherring-Gesellschaft f̈r Synchrotionstrahlung (BESSY) for the 1×1 and (3×3) R30°surfaces at a converage of 0.5 monolayer. The spin-resolved photoemission data were obtained for normal incidence of the light and normal emission of the photoelectrons. For both the 1×1 and (3×3) R30°structures we find no dispersion in the Ag photoelectron peaks depending on K and K. For the 1×1 structure and for photon energies between 20 and 24 eV, we observe an additional Ag photoelectron peak at about 1 eV higher binding energy which results from a d-level splitting due to Ag-Ag interaction. This peak is absent for the (3×3)R30°phase, which demonstrates that the Ag-Ag neighbor interaction is negligible. This supports the models that do not imply Ag-Ag interaction for the Ag adsorption in the (3 × 3) R30°phase. © 1990 The American Physical Society.