Irradiation damage in carbon-doped silicon irradiated at low temperatures by 2 MeV electrons

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Abstract
Irradiation of silicon by 2 MeV electrons at 130°K leads to the removal of carbon from substitutional sites and the formation of centres with axial symmetry having vibrational modes at 921 and 930 cm−1 for 12C; large isotope shifts are found in crystals containing 13C and 14C. This centre is considered to involve interstitial carbon atoms but not oxygen impurities. On annealing such irradiated crystals to room temperature the concentration of these centres is reduced and a new transient centre involving carbon has been detected. Further annealing leads to the formation of the well known 11.56μm absorption band in pulled crystals and it is shown that this may be correlated with another band at 1115.5 cm−1. Again large isotope effects are found in crystals containing 13C and 14C and this centre is ascribed to a [O-C] complex involving an interstitial carbon atom.