The presence of bonded C-C centers was deduced from the observation of Raman lines at 1742, 1708 and 1674/cm, in material which was co-doped with 12C and 13C, after annealing at 850C. There was an associated loss of vibrational scattering from CAs. It was found that the frequencies agreed with theoretical results for a C-C split interstitial (deep donor) that formed via the trapping of a mobile interstitial C atom (a displaced CAs) by a non-displaced CAs acceptor. A weaker Raman triplet was detected at 1859, 1824 and 1788/cm, and was attributed to another C-C complex. The assignment of the 2 triplets to a single donor and to a neutral defect, respectively, was found to be consistent with an analysis that involved the loss of CAs acceptors.

J.Wagner, R.C.Newman, B.R.Davidson, S.P.Westwater, T.J.Bullough, T.B.Joyce, C.D.Latham, R.Jones, S.Oberg: Physical Review Letters, 1997, 78[1], 74-7