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

Si (111) 77 surfaces were transformed into topologically ideal, unreconstructed Si (111): As 11 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 10^7 and 10^11 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.