A theoretical study was made of the diffusion barriers, Ti and Cu, in crystalline samples, and of the interactions between these elements and H. Calculations were performed by using molecular cluster and Hartree-Fock methods. Use of the partial retention of diatomic differential overlap method predicted diffusion barriers of 3.29eV for Ti+, 2.25eV for Tio, and 0.24eV for Cu+. The latter method also predicted that substitutional Tio was a deep trap for interstitial H, with a gain in energy of 1.84eV (relative to atomic H which was far from the cluster). First-principles Hartree-Fock calculations showed that a Ti+ ion at a tetrahedral interstitial site also formed a bond with interstitial H. This involved a dissociation energy of 2.31eV. On the other hand, interstitial Cu+ did not form a bond with H.

D.E.Woon, D.S.Marynick, S.K.Estreicher: Physical Review B, 1992, 45[23], 13383-9

Table 164

Diffusivity of H in Polycrystalline Si