It was noted that a H plasma had a marked effect upon dislocation mobility in Si, and reduced its activation energy to 1.2eV. By applying density functional theory to the interaction of H or H2 with the core of a 90º partial dislocation, it was found possible to identify a path which involved kink formation and migration at hydrogenated core bonds and which conformed exactly with experimentally measured activation energies. The low pre-factor value, which depended upon the H concentration, arose from the low mean-free path of H-soliton-kink complexes under a substantial flux of H atoms. In comparison, the activation energy for dislocation motion in intrinsic material, via the soliton mechanism, included the thermal equilibrium concentration of solitons and involved an activation energy of at least 1.8eV. The alternative mechanism assumed fully reconstructed kinks and was found to involve an activation energy of 1.8 to 1.9eV within Hirth-Lothe theory, unlike the 1.2eV which was obtained by applying the same theory to other recent results. The experimental values were of the order of 2.2eV. If obstacles limited dislocation motion, then it was suggested that – during H-catalyzed motion - these obstacles were either released by the passage of the free soliton or were etched away by H. It was thought possible that a mechanism which involved H2 was involved, especially at lower temperatures, and clear evidence was found that H2 was attracted to the large channel of the dislocation core; being 0.29eV lower in energy than was interstitial H2.

H Interaction with Dislocations in Si C.P.Ewels, S.Leoni, M.I.Heggie, P.Jemmer, E.Hernández, R.Jones, P.R.Briddon: Physical Review Letters, 2000, 84[4], 690-3