General trends of the carbon penetration in Si(001) surfaces

We present a Monte Carlo study on the general trends of the carbon incorporation in Si(001) surfaces in presence of an increasing number of carbon atoms or surface defects such as silicon or germanium ad-dimers. Our results emphasize two possible ways of improving the carbon penetration in the Si(001) subsurface region: (i) increasing the carbon coverage from a single carbon atom per unit cell to a carbon monolayer; (ii) increasing the number of ad-dimers. Combining both effects leads to an appreciable amelioration of the carbon contents in the subsurface layers. Acting on the ad-dimer location with respect to the silicon dimer rows favours the carbon penetration even further. The influence of other parameters such as the ad-dimer-ad-dimer distance or the chemical nature of the defects (silicon or germanium) is also investigated.