EVIDENCE OF SUBSTRATE METALLIZATION BY LI ADSORPTION ON THE SI(001) SURFACE

We report an evidence of substrate metallization induced by Li adsorpt ion on the Si(001) surface, based on the combined results of electron energy-loss (EEL) and angle-resolved photoemission (ARP) measurements. The metallic surface at a low dose of Li manifests itself as a loss p eak due to an intraband surface plasmon in EEL spectra and a metallic peak in ARP spectra. These peaks are coherently understood in terms of substrate metallization, where electrons from Li adatoms partially oc cupy the empty substrate surface bands. Furthermore, the unique negati ve dispersion of the plasmon reveals that local field effects may caus e such an anomalous dispersion.