  First-principles calculations of work function tuning induced by different
chemical terminations on Si(100) surface are presented and discussed. We find
that the presence of halogen atoms (I, Br, Cl, and F) leads to an increase of
the work function if compared to the fully hydrogenated surface. This is a
quite general effect and is directly linked to the chemisorbed atoms
electronegativity as well as to the charge redistribution at the interface. All
these results are examined with respect to previous theoretical works and
experimental data obtained for the (100) as well as other Si surface
orientations. Based on this analysis, we argue that the changes in the
electronic properties caused by variations of the interfacial chemistry
strongly depend on the chemisorbed species and much less on the surface crystal
orientation.
