Re-investigation of the Bi-induced Si(111)-() surfaces by low-energy electron diffraction

The atomic structures of the Bi/Si(111)-( 3 × 3 ) reconstructed surfaces obtained at different adsorbate coverages were studied by dynamical low-energy electron diffraction (LEED) I–V analysis. The experimentally obtained I–V curves of the β-Bi/Si(111)-( 3 × 3 ) surface, which is formed by a Bi coverage of 1 ML, showed good agreement with the curves calculated for the milk stool model, a model proposed in the literature. In contrast to this result, the I–V curves of the α-phase obtained at a coverage of 1/3 ML do not agree with those reported in early LEED studies. We found that the I–V curves reported in the former LEED studies resemble closely to the results obtained for the surface on which the β and α-phases coexist. Based on the obtained I–V curves, we propose a more reliable structural model for the α-phase, and present the way to determine the presence of a high quality α-phase by using LEED.