Three carbon pairs in Si
Carbon is a common impurity in Si. Studies of this impurity have been carried out for decades, both experimentally and theoretically. The most common C-related defects are the isolated substitutional (Cs) and interstitial (Ci) impurity, the CiCs pair, and the CsCs pair. Existing theoretical studies explain some features of these defects, but not all the experimental data. In particular, two CiCs pairs have been observed and studied theoretically, but theory fails to predict their observed relative stability in various charge states. Theory also suggests that a third CiCs configuration should exist, but it has never been seen. Furthermore, the possibility of a CiCi pair has not been explored. In this thesis, we study systematically the properties of isolated C and all of the possible carbon pairs in silicon. The geometries, relative energies, migration paths and barriers, binding energies, electrical activity, and vibrational spectra, are calculated and compared to experimental data when available.