Epitaxial growth of Sn on Si(111): A direct atomic-structure determination of the (2 √3 ×2 √3 )R30° reconstructed surface

Scanning tunneling microscopy (STM) has been used to determine the surface atomic structure of Si(111)(2{}3 ×{}2 {}3 )-Sn. The topographic images show four resolved atoms in each (2 {}3 ×{}2 {}3 ) unit cell, and the structure is found to be onefold symmetric. Together with coverage measurements, the STM analysis implies that the reconstructed surface is an epitaxial Sn two-layer structure, where the atoms adopt a bonding configuration characteristic of {α}-Sn. A three-dimensional structure model, in accordance with the obtained results, is proposed.