Unoccupied surface-state bands on the single-domain Si(100)2 × 1 surface

We have studied the unoccupied surface bands of single-domain Si(100)2 × 1 surfaces with angle-resolved inverse photoemission (IPE). Two surface states are present near the Fermi level (EF) with flat energy dispersions at 1.1 and ∼ 0.4 eV above EF along the Γ-J direction, while along the Γ-J′ direction these state are dispersive with an apparent crossing at about halfway towards J′. Both surface bands are assigned to the empty dangling-bond states. As only one empty dangling-bond band is expected for a 2 × 1 reconstruction, we attribute the appearance of two branches to domains of asymmetric dimers on the surface, arranged into local p(2 × 2) or c(4 × 2) periodicities. These findings are analogous to the results of recent angle-resolved (direct) photoemission studies of the filled dangling bonds on the 2 × 1 and the cooled c(4 × 2) surfaces. © 1992.