Nanometer-scale Si selective growth on Ga-adsorbed voids in ultrathin SiO 2 films

Abstract

We examined nanometer-scale Ga selective doping by Si growth on Ga-adsorbed voids in ultrathin silicon-dioxide on Si(111) surfaces. The doping processes were observed by scanning tunneling microscopy (STM). Voids in ultrathin oxide films were plugged with a ( 3 × 3 )-Ga structure, and the selective growth was performed by introducing disilane gas (Si 2H 6). Si crystals were selectively grown only in the voids at 460–550°C. Two-dimensional nucleation was found to start from the edge of the voids. Incorporated Ga atoms mostly segregated during the selective growth and were reconstructed to the ( 3 × 3 ) structure by annealing at 600°C. These results show that Ga doped dots of nanometer-scale can be formed by selective epitaxial growth using an ultrathin silicon-dioxide mask.