Re-investigation of the Bi-induced Si(111)-(sqrt(3) × sqrt(3)) surfaces by low-energy electron diffraction

The atomic structures of the Bi/Si(111)-(sqrt(3) × sqrt(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)-(sqrt(3) × sqrt(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.