Split and sealing of dislocated pipes at the front of a growing crystal

A model is suggested for the split of dislocated pipes at the front a growing crystal. Within the model, the pipe split occurs 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 are calculated. The parameter regions are determined at which the expansion of the dislocation semi‐loop is energetically favorable and, thus, the pipe split becomes irreversible. A mechanism is proposed for the formation of a stable semi‐loop resulting in the split and possible subsequent overgrowth of the dislocated pipe. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)