Structural and electronic properties of boron-induced defects on the Si(001) surface

Abstract

The (001) surface of heavily boron (B) doped silicon is investigated by employing the scanning tunneling microscopy measurements and the density functional theory calculations. Two different defect structures are found in the surface layers, both of which evolve the characteristic spectral features near the valence band maximum. One of the two incorporates a B atom in the second layer with the Si dimers intact and is scattered randomly in the layer. The other one incorporates a B atom in the fourth layer with a dimer vacancy produced directly above it and tends to get together with nearby dimer vacancies to grow the extended or line defects along the perpendicular direction to the dimer rows. Such defect formation is energetically favored to enhance the B populations in the second and fourth layers by $\ensuremath{\sim}120$ and $\ensuremath{\sim}80$ times, respectively, when compared to that in the bulk layer.