EMPTY SURFACE-STATES ON THE SI(100) 2X1-K SURFACE - EVIDENCE FOR OVERLAYER METALLIZATION

The electronic structure of potassium-covered single-domain Si(100)2 x 1 surfaces has been studied with angle-resolved direct (ultraviolet) and inverse photoemission at room temperature. At saturation coverage, the surface is metallic due to the filling of the minimum of a strongly dispersive empty surface state of mainly K 4p(z) character. Paraboliclike dispersions are observed for this state in the GAMMABAR-JBAR' and the GAMMABAR-JBAR directions (i.e., both along and perpendicular to the dimer rows), showing the metallic bonding in the overlayer and a strong K-K interaction in both directions.