ELECTRONIC-PROPERTIES OF (2XN)-BI RECONSTRUCTIONS ON SI(100)

Annealing of a thin Bi layer grown on the Si(100)-(2 x 1) surface is k nown to produce well-ordered (2 x n) reconstructions. To investigate t he Bi-induced electronic properties in these different structural conf igurations, we present ultraviolet photoemission and high-resolution e lectron energy loss spectroscopies on this interface. The adsorption o f Bi produces clear modification of the substrate dimer-related surfac e states. On the (2 x n)-Bi reconstructed phases the data show a clear semiconducting behaviour, with the opening of a surface gap larger (1 .3 eV) than that observed on the clean Si(100)-(2 x 1) surface (0.4 eV ). Moreover, electronic states are detected within the gap up to 280 d egrees C annealing temperature, whose possible origin is discussed. Th e absence of electronic excitations in the enlarged gap region and the modified density of occupied states observed for higher annealing tem peratures (< 500 degrees C) suggest that the Bi adatoms induce breakin g of the underlying Si-Si dimers.