STM study of the C-induced Si(100)-c(4X4) reconstruction -: art. no. 115321

We report a direct and reliable way to produce the Si(100)-c(4x4) reconstruction by submonolayer deposition from a SiC source and subsequent annealing. Auger electron spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy (STM) investigations reveal that a C amount equivalent to 0.07 monolayers (ML's) is sufficient to obtain full coverage of the c(4x4) reconstruction. A deposition of 0.035 ML's C produces a c(4x4) coverage of only 19%, indicating that C is not only present in the c(4x4) areas, but also in the 231 areas. There is not enough C to make it a regular part of the c(4x4) reconstruction and we therefore conclude that the c(4x4) reconstruction is strain induced. We find that a combination of the mixed ad-dimer and buckled ad-dimer models explains all main features observed in the STM images. Images of freshly prepared c(4x4) surfaces exhibit a decoration of approximately 50% of the unit cells, which is attributed to perpendicular ad-dimers. Long exposures (>20 h) to the UHV background gas quench these features and the c(4x4) reconstruction appears as if more homogeneous.