A model was suggested for the split of dislocated pipes at the front a growing crystal. Within the model, the pipe split occurred through the generation of a dislocation semi-loop at the pipe and crystal surfaces and its subsequent expansion into the crystal interior. The strain energy of such a dislocation semi-loop as well as the stress field of a dislocated pipe perpendicular to a flat crystal surface were calculated. The parameter regions were determined at which the expansion of the dislocation semi-loop was energetically favorable and, thus, the pipe split became irreversible. A mechanism was proposed for the formation of a stable semi-loop resulting in the split and possible subsequent overgrowth of the dislocated pipe.

Split and Sealing of Dislocated Pipes at the Front of a Growing Crystal. M.Y.Gutkin, A.G.Sheinerman: Physica Status Solidi B, 2004, 241[8], 1810-26