Annealing of a thin Bi layer grown on the Si(100)-(2 x 1) surface is known to produce well-ordered (2 x n) reconstructions. To investigate the Bi-induced electronic properties in these different structural configurations, we present ultraviolet photoemission and high-resolution electron energy loss spectroscopies on this interface. The adsorption of Bi produces clear modification of the substrate dimer-related surface 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 degrees C annealing temperature, whose possible origin is discussed. The absence of electronic excitations in the enlarged gap region and the modified density of occupied states observed for higher annealing temperatures (< 500 degrees C) suggest that the Bi adatoms induce breaking of the underlying Si-Si dimers.
- surface electronic phenomena