Adsorption of C-based molecules at the Si surface: the initial stages of SiC growth, from ab-initio simulations.

We review some recent results on the adsorption mechanisms of C atoms and molecules at the Si(001) and Si(111) surfaces via ab-initio molecular dynamic simulations at finite temperature. Our calculations show that for all the adsorbed species, and substrate orientations, at low temperatures the preferred adsorption sites stay at the surface: This is accomplished through the formation of Si-C bonds with a distortion of the molecule to optimize the Si-C distance at the SiC bulk bond length. At higher temperatures, around 1000K,incorporation of C atoms becomes possible,via a modification of the substrate. The implication of our results for the initial stages of SiC growth will be discussed. Part of the work was done in the frame of INFM Project PRA-1MESS.