SUDDEN BEGINNING OF METALLIC BEHAVIOR AT AG SI(100) INTERFACE - A REAL-TIME PHOTOREFLECTANCE-SPECTROSCOPY INVESTIGATION/

The Ag growth of Si(100)-2 X 1 has been investigated by real-time in s itu photoreflectance spectroscopy, in the spectral range 1. 1-5.4 eV. For the lowest coverages, the interface displays a nonmetallic charact er, due to the covalent bonding between the Ag atoms and the Si atoms. When the Ag coverage increases, the additional deposits become sudden ly metallic and the differential reflectance spectra display typical f eatures: rapid increase of the signal in the red and near-infrared ran ge because of the optical response of the conduction electrons; appear ance and growing of a plasma resonance in the thin Ag deposits. Moreov er, the following of the signal during the Ag growth permits accurate determination of the beginning of the metallic behavior.