Sn-induced c(4 x 4) reconstruction on the C-incorporated Si(001)-4° off surface

The reconstruction induced by Sn atoms on the C-incorporated Si(001)-4 degrees off surface has been studied using scanning tunneling microscopy and synchrotron photoemission spectroscopy. When 0.6-ML Sn atoms were deposited on the Si(001)-4 degrees off surface with subsurface C atoms at 630 degrees C, the whole (001) terraces were covered with a single c(4x 4) reconstruction, where each Sn addimer bridges two Si dimers, reducing the density of dangling bonds to 0.5 ML. Such a reconstruction is different from the Sn-induced c(8 x 4) reconstruction formed on the clean Si(001) terraces without subsurface C atoms, where Sn dimers replace Si dimers and every fourth dimer is vacant. In both cases, the adjacent dimers buckle out of phase and the DB steps are debunched into single-layer steps. The reconstruction change from c(8 x 4) to c(4 x 4) is explained by the surface stress exerted by the subsurface C atoms much smaller than Si atoms.

Automated summary

The effect of Sn atoms on the C-incorporated Si(001)-4 degrees off surface was investigated. The deposition of 0.6-ML Sn atoms on the surface with subsurface C atoms resulted in a c(4x 4) reconstruction, where each Sn addimer bridges two Si dimers. This is in contrast to the c(8 x 4) reconstruction formed on the clean Si(001) terraces without subsurface C atoms, where Sn dimers replace Si dimers and every fourth dimer is vacant. The change in reconstruction is attributed to the smaller surface stress exerted by subsurface C atoms compared to Si atoms.