UNOCCUPIED SURFACE-STATE BANDS ON THE SINGLE-DOMAIN SI(100)2X1 SURFACE

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