ICDS Conference, Sendai, Japan, 7.95
Abstract
The C_i and C_s-C_i defects in Si exhibit several unexplained properties. In the neutral charge state, the C_i defect possesses two almost degenerate vibrational modes suggesting a trigonal defect in disagreement with the C_2v symmetry deduced from several experiments. The B-form of the second defect is believed to consist of a Si interstitial, Si_i, located near a BC site between two C_s atoms, in apparent conflict with the results of PL experiments which show that the C-related vibrational modes are decoupled. The structure and vibrational modes of both defects are analysed using LDF cluster theory. The degeneracy of the modes o f C_i is attributed to an almost D_3h structure, with a 3-fold axis along [01-1]. The modes of the di-carbon interstitial lead to a resolution of the long standing problem concerning the almost zero-shifts due to mixed isotopes in the 580 and 543 cm-1 local modes observed in PL studies.
Keywords: ab initio theory, carbon interstitials, silicon, vibrational modes
C.E. 7.95