Low-energy electron diffraction as a direct identification technique: Atomic structures of Ag- and Li-induced Si(111)-(√3 × √3 )R30°

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Abstract
Quantitative low-energy electron-diffraction (LEED) IV spectra analyses of Ag, Li, and metastable clean (√3 × √3 )R30 ° Si(111) reveal that striking similarities in the LEED spectra are due to common scattering blocks of substrate atoms while the metal atoms are adsorbed at open sites on the Si lattice. This leads to the use of LEED IV spectra as a characterization method. For the (√3 × √3 )R30 ° phases of Li and Ag on Si(111), it is found that both structures can be described by a modified honeycomb-chained-trimer model. The main structural element consists of Si trimers and Si atoms in the deeper reconstructed layers. A counterexample is provided by Si(111)-(√3 × √3 )R30 °-Au for which the IV spectra are very different from those of the other three systems because the common scattering block is absent.