Comparison of carbon incorporation on the clean and hydrogenated Si(001) reconstructed surfaces

The size difference between carbon and silicon makes carbon incorporation in a silicon matrix difficult. We present here, in the framework of first-principle calculations, a systematic comparison of the initial stages of carbon penetration in the hydrogenated and non-hydrogenated Si(0 0 1) surfaces. The effect of the carbon position with respect to the surface predominates in the dihydrure phase, while the nature of the carbon adsorption site (alpha or beta) plays the main role in the case of the non-hydrogenated surface. In both cases, C-C interactions can modify these schemes and third neighbour positions are favoured in the fourth and fifth layers, as observed in the silicon bulk. An energetic study as a function of the carbon chemical potential in the 0 to -7.4 eV range shows no transition points at which the preferred structures could change. (C) 2002 Elsevier Science B.V. All rights reserved.