Acetylene on Si(111): 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 degreesC. With increasing temperature, up to 950 degreesC, we have observed a substantial increase of the C atoms mainly bounded to silicon in nonsubstitutional sites in a nearly planar sp(2) 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. (C) 2001 Elsevier Science B.V. All rights reserved.