Nanometer-scale Si selective growth on Ga-adsorbed voids in ultrathin SiO2films

We examined nanometer-scale Ga selective doping by Si growth on Ga-adsorbed voids in ultrathin silicon-dioxide on Si(lll) surfaces. The doping process es were observed by scanning tunneling microscopy (STM). Voids in ultrathin oxide films were plugged with a (root 3 x root 3)-Ga structure, and the se lective growth was performed by introducing disilane gas (Si2H6). Si crysta ls were selectively grown only in the voids at 460-550 degrees C. Two-dimen sional nucleation was found to start from the edge of the voids. Incorporat ed Ga atoms mostly segregated during the selective growth and were reconstr ucted to the (root 3 x root 3) structure by annealing at 600 degrees C. The se results show that Ga doped dots of nanometer-scale can be formed by sele ctive epitaxial growth using an ultrathin silicon-dioxide mask. (C) 1999 El sevier Science B.V. All rights reserved.