Geometric and electronic structure of Sb on Si(111) by scanning tunneling microscopy

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Abstract
Scanning tunneling microscopy and spectroscopy (STS) are used to investigate the Si(111)-Sb surface. At an Sb coverage of a few percent of a monolayer (ML), Sb substitutes Si adatoms in the 7×7 reconstruction. At about 1/3 ML, the 7×7, ‘‘disordered 7×7,’’ and √3 × √3- R30° reconstructions are observed. This sub-ML √3 × √3 reconstruction is a simple adatom phase. The T4 site is identified as the chemical bonding site of Sb adatoms in these low-coverage reconstructions. Spatially resolved STS shows the complex nature of the electronic structure of Si(111)7×7-Sb as compared to the clean Si surface. At the saturation coverage of 1 ML, domains of 1×1, 2×1, and a different √3 × √3 reconstruction are observed, and structure models are proposed.