STM study of surface reconstructions of Si(111):B.

The scanning tunneling microscope is used to study the boron-doped Si(111) surface as a function of annealing times and temperatures. The surface structure is found to be determined by the concentration of B. When the substitutional B concentration is less than 1% of the top 1[times]1 bilayer atoms, the surface is largely 7[times]7 but surrounded by adatom-covered 1[times]1 regions (which have higher B concentration). When the B concentration is more than 3%, the whole surface will be adatom-covered 1[times]1 regions including ([radical]3 [times] [radical]3 )[ital R]30[degree] structures. The ([radical]3 [times] [radical]3 )[ital R]30[degree] domains will increase with the B concentration. Because 7[times]7 can only exist in the region with low B concentration, the growth of 7[times]7 is slowed down. Further annealing at 560 [degree]C can convert 2[times]2, [ital c](4[times]2) into 7[times]7 and 9[times]9. Sides of the 7[times]7 domain preferentially grow along the three equivalent [11[bar 2]] directions. The adatom-covered 1[times]1 regions are bounded by faulted halves of the 7[times]7 domains. The dark sites of 7[times]7 are observed and counted. They are further interpreted in terms of a B substitution model. The pattern of bright and dark atoms in ([radical]3 [times] [radical]3 )[ital R]30[degree] domains is analyzed and a criterion formore » a B stabilized Si-([radical]3 [times] [radical]3 )[ital R]30[degree] structure is obtained.« less