This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.New experimental and theoretical results on the silicon diinterstitial (I 2 ) and its interactions with oxygen and carbon impurity atoms in Si crystals are reported. Electronic structure calculations indicate that I 2 has an acceptor and a donor level in the gap, which are close to the conduction and the valence band edges, respectively. Experimental results, which support the theoretically predicted high mobility of I 2 , are discussed. It is argued that mobile I 2 can be trapped by oxygen and carbon impurities. The I 2 O center has a donor level at E v þ0.09 eV. Two absorption bands at 936 and 929 cm À1 are assigned to the local vibrational modes of the I 2 O defect in the neutral and positively charged states, respectively. The binding energy of I 2 O relative to the separated I 2 and O i species is 0.22 eV. The disappearance of the I 2 O complex upon thermal annealing occurs in the temperature range 50-100 8C and is accompanied by the introduction of another defect, which gives rise to two hole emission signals from energy levels at E v þ0.54 and E v þ0.45 eV. It is argued that these levels are related to a complex consisting of interstitial carbon and interstitial silicon atoms (C i I). The stable configurations of the C i I pair have been found.

The evolution of radiation-induced carbon-related defects in low temperature irradiated oxygen containing silicon has been studied by means of Fourier transform infrared absorption spectroscopy (FTIR) and deep level transient spectroscopy (DLTS). FTIR measurements have shown that annealing of interstitial carbon atom Ci, occurring in the temperature interval 260-300 K, results in a gradual appearance of a number of new absorption bands along with the well known bands related to the CiOi complex. The new bands are positioned at 812, 910.2, 942.6, 967.4 and 1086 cm-1. It has been found that the pair of bands at 910 and 942 cm-1 as well as another set of the bands at 812, 967.4 and 1086 cm-1 display identical behavior upon isochronal annealing, i.e. the bands in both groups appear and disappear simultaneously. The disappearance of the first group occurs at T = 285-300 K while the second group anneals out at T = 310-340 K. These processes are accompanied by an increase in intensity of the bands related to CiOi. It is suggested that intermediate states (precursors) are formed upon the transformation from a single (isolated) Ci atom to a stable CiOi defect. The results obtained in DLTS studies are in agreement with the FTIR data and show unambiguously the formation of CiOi precursors with slightly lower activation energy for the hole emission as compare to that for the main CiOi state.

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Phone: þ38 044 525 98 21, Fax: þ38 044 525 15 89We report the data on the electronic absorption of interstitial boron-related defects in silicon, irradiated with 5 MeV electrons. Two new electronic absorption features have been revealed in the spectrum of boron-doped Si. The sharp line at 4385.2 cm À1 is detected in Si irradiated at 80 K and subjected to the subsequent annealing up to 300 K. The emergence of the registered line depends on the concentration of boron and does not depend on the presence of oxygen and carbon in the samples. The revealed line is associated with B i B s complex. It is shown that the presence of oxygen in the samples inhibits the formation of B i B s defects. The disappearance of the 4385.2 cm À1 line upon annealing is accompanied by the emergence of a line at 7829.5 cm À1 in the spectrum. The appearance of the 7829.5 cm À1 line depends on the presence of carbon in the samples. The registered 7829.5 cm