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

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\ifmmode\times\else\texttimes\fi{}7 reconstruction. At about 1/3 ML, the 7\ifmmode\times\else\texttimes\fi{}7, ``disordered 7\ifmmode\times\else\texttimes\fi{}7,'' and \ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}3- R30\ifmmode^\circ\else\textdegree\fi{} reconstructions are observed. This sub-ML \ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}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\ifmmode\times\else\texttimes\fi{}7-Sb as compared to the clean Si surface. At the saturation coverage of 1 ML, domains of 1\ifmmode\times\else\texttimes\fi{}1, 2\ifmmode\times\else\texttimes\fi{}1, and a different \ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}3 reconstruction are observed, and structure models are proposed.