Parallel Adatom Chains on Si(111): A Chemisorption-Induced Surface Reconstruction

Abstract

Using surface x-ray scattering, we have studied a (3 \ifmmode\times\else\texttimes\fi{} 1) Si(111) reconstruction induced by chemisorption of Ca${\mathrm{F}}_{2}$. This reconstruction consists of a parallel array of zigzag Si adatom chains oriented along 1\ifmmode\bar\else\textasciimacron\fi{}10>. The orbitals on the Si chain atoms rehybridize into ${p}_{x}$ and ${p}_{y}$ along the surface to form $\ensuremath{\sigma}$ bonds, and parallel ${\mathrm{sp}}_{z}$ orbitals perpendicular to the surface to give additional $\ensuremath{\pi}$ bonding. This basic structure, with no dangling bonds at only ⅓ monolayer adsorbate coverage, may explain the occurrence of (3 \ifmmode\times\else\texttimes\fi{} 1) reconstructions among a diverse range of Si-adsorbate systems.