Ion scattering Spectroscopy study of Si(001)c(4 x 4)-C surface reconstruction

Reconstructed Si(001)c(4 x 4)-C surface has been studied by coaxial impact collision ion scattering spectroscopy (CAICISS). When 100L ethylene (C2H4) was exposed on Si(001.)-(2 x 1) surface at 700 degreesC, Si(001) dimer structures were changed by induced carbon (C) atoms. The experimental CAICISS spectra and simulation results reveal that the reconstructed Si(001)c(4 x 4)-C surface shows good agreement with the missing dimer model, rather than the Si-C heterodimer model, and adsorbed C atoms influence only the reconstructed vertical plane of Si(001) surface. On comparing the azimuthal-scan curves for 100L C/Si(001) with those for clean Si(001), it can be suggested that C atoms occupy the fourth subsurface layer of Si(001) directly below the HB (bridge) site. These results are new evidence supporting the previous studies based on the C incorporation into Si(001) surface with missing dimers and the substitution of the fourth Si layers.