Empty surface states on the Si(100)2×1-K surface: Evidence for overlayer metallization

The electronic structure of potassium-covered single-domain Si(100)2×1 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 4${\mathit{p}}_{\mathit{z}}$ character. Parabolic-like dispersions are observed for this state in the Γ¯-J¯ ’ and the Γ¯-J¯ 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.