Origin of the surface metallization in single-domain K/Si(100)2x1

Abstract

The electronic structure and the metallization onset of single-domain K/Si(100)2x1 have been investigated with angle-resolved polarization-sensitive ultraviolet photoemission. The electronic states producing the surface metallization have been studied for increasing K coverages up to room-temperature saturation. As K coverage increases, the interface undergoes a transition at a critical coverage, from a low-coverage semiconducting phase, to a saturation-coverage metallic phase. Two different surface states (F-1 and F-2) have been detected in the vicinity of the Fermi level. These two states are sequentially filled along the metallization process. The coverage dependence of both F-1 and F-2, and their symmetry properties indicate that the metallization is due to the filling of an initially empty surface band (appearance of F-2) We relate F-1 to the completion of K chains in the single-domain surface. The changes detected in K 3p line shape correlate well with the modifications of the valence band, and support that the surface remains semiconducting up to the filling of F-2.