Native defects in Si were readily created during a variety of processes. They diffused rapidly and interacted with themselves, with each other, and with many impurities; especially H. Vacancy-H complexes were better understood than were self-interstitial–H ones, except for one of the {I,H2} complexes, which was detected by infra-red absorption spectroscopy and predicted theoretically. The interactions between 1 neutral self-interstitial, and up to four H impurities, were studied systematically by using first-principles molecular-dynamics simulations; with basis sets which consisted of linear combinations of atomic orbitals. Except for n = 1, each of the {I,Hn} complexes had at least 1 metastable configuration. One family of structures had two H atoms bound to the same Si atom. Another family of structures had a single H atom bound to each Si atom; thus forming a so-called zig-zag chain of Si-H bonds. The former complexes were more localized, with H tying up bonds at the defect itself. The latter complexes were more extended, and illustrate how H relieved the lattice strain associated with a defect. The experimentally observed {I,H2} complex was the most stable of the series. It was found that total energy differences and electronic structures were sensitive to the sampling process, even when using 128 host-atoms cells. For the type of defects described here, more than 4 sample points could be needed to achieve adequate convergence.

Self-Interstitial–Hydrogen Complexes in Si. M.Gharaibeh, S.K.Estreicher, P.A.Fedders, P.Ordejón: Physical Review B, 2001, 64[23], 235211 (7pp)