Scanning tunneling microscopy (STM) has been used to determine the surface structure of the √3 × √3 reconstruction induced by Bi on the Si(111) surface. The STM images show that there are two distinct ordered surfaces with √3 × √3 periodicity. At 1/3-monolayer Bi coverage, the √3 × √3 phase consists of one Bi adatom per unit cell adsorbed at ${\mathit{T}}_4$ sites on a Si(111) bilayer. At nearly one monolayer of Bi coverage, STM images show protrusions with a complex shape dependent on bias voltage. These STM images are discussed and compared with structural models derived from previous experimental studies.

• Received 26 March 1993

DOI:https://doi.org/10.1103/PhysRevB.48.4895