Crystalline samples which were doped with C were irradiated with electrons and then implanted with protons. Infra-red absorption measurements revealed local modes of H and C, at 2967.4, 911.7 and 654.7/cm, which originated from the same defect. Measurements of samples which were co-doped with various C and H isotopes showed that the defect contained 2 equivalent C and 2 equivalent H atoms. Uniaxial stress measurements showed that the defect had trigonal symmetry. First-principles local density functional theory was used to calculate the structure and local vibrational modes of defects involving pairs of equivalent C and H atoms. On the basis of the results, the observed local modes were attributed to a defect having 2 adjacent substitutional C atoms; each of which bonded with a H atom which was located between the C atoms.

Combined Infrared Absorption and Modelling Study of a Dicarbon-Dihydrogen Defect in Silicon. E.V.Lavrov, L.Hoffmann, B.Bech Nielsen, B.Hourahine, R.Jones, S.Oberg, P.R.Briddon: Physical Review B, 2000, 62[19], 12859-67