Electronic structure, atomic structure, and the passivated nature of the arsenic-terminated Si(111) surface

Abstract

Si(111)7\ifmmode\times\else\texttimes\fi{}7 surfaces were transformed into topologically ideal, unreconstructed Si(111):As 1\ifmmode\times\else\texttimes\fi{}1 surfaces by exposure to ${\mathrm{As}}_{4}$ molecules. The As atoms replace the outermost Si atoms resulting in a surface with As lone-pair states instead of Si dangling-bond states. This structure is confirmed by a comparison between the lone-pair dispersion, derived from angle-resolved photoemission, and theoretical surface bands, obtained from a first-principles pseudopotential calculation. The As-terminated surface is highly passivated as a result of the existence of the As lone-pair states and is shown to be almost unaffected by oxygen and air exposures as high as ${10}^{7}$ and ${10}^{11}$ L [1 L (langmuir)${=10}^{\mathrm{\ensuremath{-}}6}$ torr sec], respectively. Initial energies for bulk direct transitions were determined and found to be in good agreement with those predicted using initial states calculated with an empirical pseudopotential method and a free-electron parabola for the final-state band.