ON THE STAND-OFF POSITIONS OF MISFIT DISLOCATIONS

A comparative analysis for the results obtained by force and energetic approaches, which are used in calculations of equilibrium position of misfit dislocations near interfaces, is performed. It is shown that a correct utilization of both approaches leads to similar results for t he models which do not consider the finite thickness of contacting pha ses. The peculiarities of the dislocation motion to the equilibrium st and-off positions are considered in the framework of the force approac h. In the case of climbing misfit dislocations local inelastic variati on of the material volume caused by diffusive point defects is taken i nto account. This results in the calculated values of stand-off distan ces which are in a good agreement with those observed by Mader in the system Nb-Al2O3 (the system was produced by internal oxidation at high temperature). The slip of misfit dislocations in the planes inclined to the interface is proposed as another possible mechanism for the mot ion of misfit dislocations to their equilibrium positions (such a mech anism is peculiar to an epitaxial growth). An exact equation allowing to calculate the misfit dislocation equilibrium positions in a thin tw o-layer plate is derived with accounting for all the boundary conditio ns of the problem. A simple analytical form for a stand-off position o f a gliding misfit dislocation is found. It is predicted that a stand- off distance can vary from two to four times in dependence on the rati o of the layer thicknesses. A quantitative estimate of stand-off dista nce gives values which are in accordance with the experimental observa tions by Mayer et al.