Observation of the Si(100)“1×2”-Ba surface by scanning tunneling microscopy

Abstract

We have studied the $``1\ifmmode\times\else\texttimes\fi{}2''$ structure on $\frac{1}{2}$ ML Ba/Si(100) by scanning tunneling microscopy (STM). This phase has two mirror symmetric unit cells, $(4,0)\ifmmode\times\else\texttimes\fi{}(1,2)$ and $(4,0)\ifmmode\times\else\texttimes\fi{}(1,\ensuremath{-}2).$ Their combination leads a wavy structure in STM images. We discuss the structure in comparison with previous low-energy electron-diffraction studies, and propose a model of the $``1\ifmmode\times\else\texttimes\fi{}2''$ structure where buckled Ba dimers locate on the second Si layer reconstructed into a dimerized $``1\ifmmode\times\else\texttimes\fi{}2''$ phase.