Local Structure ofNH2onSi(100)−(2×1)and its Effect on the Asymmetry of the Si Surface Dimers

Abstract

A scanned-energy mode photoelectron diffraction study of the $\mathrm{Si}(100)\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}1)$ surface with adsorbed $\mathrm{NH}{}_{2}$ provides quantitative determination of key structural parameters previously only predicted from theoretical calculations. In particular, the $\mathrm{N}$ atoms occupy off-atop sites at a dimerized surface Si atom with N-Si bond lengths of $1.73\ifmmode\pm\else\textpm\fi{}0.08\AA{}$ and bond angle relative to the surface normal of $21\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}4\ifmmode^\circ\else\textdegree\fi{}$. The adsorption greatly reduces the Si dimer asymmetry relative to that of the clean surface.