Bias dependence and defect analysis of Bi on Si(111) 3×3β -phase

We investigate the Bi on Si(111) $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$-phase surface reconstruction using scanning tunneling microscopy. Details of the bias-dependent images of both the reconstruction and defects are presented. Combining our experimental data with density-functional theory calculations, it is confirmed that the honeycomb pattern at low-bias empty states and hexagonal closest-packed pattern at high-bias empty states originate from the Bi ${p}_{x}, {p}_{y}$ states and Bi, Si overlapped states outside bulk band gap, respectively. Analysis of the defect images and their associated densities of states provides further insight into the electronic structure of the surface. In particular, we note the presence of a quantum-dotlike localized state associated with an $\ensuremath{\alpha}$-phase defect structure. These results pave the way for further development of surface structures based on Bi on Si(111) surface with unique electronic properties such as sizable spin-orbit coupling, which might be suitable candidates for spintronic applications.