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

Si(111)7×{}7 surfaces were transformed into topologically ideal, unreconstructed Si(111):As 1×{}1 surfaces by exposure to As₄ 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 10⁷ and 10¹¹ L [1 L (langmuir)=10^-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.