INITIAL-STAGES OF IN ADSORPTION ON SI(111) 7X7

Scanning tunneling microscopy and scanning tunneling spectroscopy have been used to study the initial stages of room-temperature deposition of In on a Si(111) 7x7 surface. Individual In atoms are observed resid ing atop the substrate Si adatoms and rest atoms at T-1 sites, showing different geometric configurations. An analysis of the In atomic stru ctures in the dual-bias scanning tunneling microscopy images leads us to conclude that the In half-filled p(z)-like sp(3) hybrids covalently bond to the Si partially filled p(z)-like sp(3) hybridized orbitals a nd the In p(x,y)-like sp(3) hybrids overlap with these on the nearby m etal atoms, also showing the covalent bonding. This is also supported by the scanning tunneling spectroscopy spectrum energy measurements ab out the Fermi level where the covalent bonding between the In and Si s aturates the Si intrinsic metallic surface states, producing a surface band gap similar to 1.7 eV. (C) 1996 American Vacuum Society.