ELECTRON CORRELATION, METALLIZATION, AND FERMI-LEVEL PINNING AT ULTRATHIN K SI(111) INTERFACES/

In this paper we present a detailed photoemission study of the K/Si(11 1)7X7 and K/Si(111)(square-root 3 X square-root 3)R 30-degrees-B inter faces. Angle-resolved valence-band spectroscopy reveals the presence o f an almost dispersionless interface state below E(F). Both interfaces are clearly nonmetallic at room-temperature saturation coverage. We c ritically address the issues of charge transfer and Fermi-level pinnin g by a detailed analysis of the K 3p and Si 2p core-level spectra. We conclude that, up to saturation coverage, correlation effects determin e the electronic properties of these interfaces. Metallization occurs during the development of the second layer at cryogenic temperatures.