ANGLE-RESOLVED PHOTOEMISSION-STUDY OF THE LI-INDUCED STRUCTURES OF THE SI(001) SURFACE

We have investigated dispersion relations of surface bands induced by Li adsorption on the Si(001) surface at room temperature by Angle-Resolved PhotoEmission Spectroscopy (ARPES). The characteristic spectral changes in the Energy Distribution Curves (EDCs) with increasing Li coverage implicate that Li adatoms occupy on-top sites of the dimer-forming silicon atoms resulting in 0.5 and 1.0 monolayers for the completion of the first two Li-induced ordered (2 x 2):Li and (2 x 1):Li phase, respectively. The unique upward dispersions of the surface bands for these Li-induced structures are ascribed to the size effect of a Li adatom. We further discuss a mechanism which might account for the metallic peak found at the early stage of Li adsorption.