Acetylene on Si(1 1 1): carbon incorporation in the growth of c-SiC thin layers

Pseudomorphic c-SiC alloys on Si(1 1 1) were grown by exposure to acetylene (C2H2) in ultra-high-vacuum conditions. The behavior of C incorporation in the lattice for different substrate growth temperatures was studied by UHV electronic techniques. We found that C atoms occupy tetrahedral substitutional sites in the Si lattice when the substrate temperature is kept below 650°C. With increasing temperature, up to 950°C, we have observed a substantial increase of the C atoms mainly bounded to silicon in nonsubstitutional sites in a nearly planar sp2 configuration. This is evidenced by the analysis of the line shape of the near-edge energy loss and by extended energy loss fine structure measurements which are particularly sensitive to the bond length around each carbon atom.