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\r\n known to produce well-ordered (2 x n) reconstructions. To investigate\r\n the Bi-induced electronic properties in these different structural\r\n configurations, we present ultraviolet photoemission and high-resolution\r\n electron energy loss spectroscopies on this interface. The adsorption of\r\n Bi produces clear modification of the substrate dimer-related surface\r\n states. On the (2 x n)-Bi reconstructed phases the data show a clear\r\n semiconducting behaviour, with the opening of a surface gap larger (1.3\r\n eV) than that observed on the clean Si(100)-(2 x 1) surface (0.4 eV).\r\n Moreover, electronic states are detected within the gap up to 280\r\n degrees C annealing temperature, whose possible origin is discussed. The\r\n absence of electronic excitations in the enlarged gap region and the\r\n modified density of occupied states observed for higher annealing\r\n temperatures (< 500 degrees C) suggest that the Bi adatoms induce\r\n breaking of the underlying Si-Si dimers.