Direct picture of the local electronic structure during the Si(111)7×7-Al Schottky-barrier formation process

Electron-energy-loss spectra taken at high resolution on low-temperature substrates reveal details of the electronic structure near the Fermi level EF and their correlation with Schottky-barrier formation. Earlier experiments indicated that the Al adatoms drastically reduce the clean-surface density of states near the Fermi level. However, we find that the EF-pinning mechanism of clean Si(111)7×{}7 is still partially active up to coverages of 0.1-0.25 monolayer. The completion of the Schottky-barrier formation process appears related to a full restoration of the metallic character.