A possible model was presented for the mechanism of screw dislocation nucleation. It was based upon synchrotron white-beam X-ray topographic and transmission optical microscopic observations of micro-pipe nucleation at inclusions of foreign matter. It was shown that incorporation of an inclusion into the growing crystal could lead to deformation of the protruding ledge which constituted the overgrowing layer. Accommodation of this deformation into the crystal lattice led to the production of pairs of opposite-sign screw dislocations which then propagated with the growing crystal. Evidence for the existence of such pairs of dislocations was reported.

The Mechanism of Micropipe Nucleation at Inclusions in Silicon Carbide. M.Dudley, X.R.Huang, W.Huang, A.Powell, S.Wang, P.Neudeck, M.Skowronski: Applied Physics Letters, 1999, 75[6], 784-6