GEOMETRIC AND ELECTRONIC-STRUCTURE OF SB ON SI(111) BY SCANNING TUNNELING MICROSCOPY

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 X 7 reconstruction. At about 1/3 ML, the 7 X 7, "disordered 7 X 7," and square-root 3 X square-root 3-R 30-degrees reconstructions are observed. This sub-ML square-root 3 X square-root 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 X 7-Sb as compared to the clean Si surface. At the saturation coverage of 1 ML, domains of 1 X 1, 2 X 1, and a different square-root 3 X square-root 3 reconstruction are observed, and structure models are proposed.