Nonuniform misfit dislocation distributions in nanoscale thin layers

Abstract

Energetic, dynamic and kinetic reasons leading to the nonuniformity in misfit dislocation (MD) distributions along the nanoscale layer interfaces are considered. It is demonstrated that they are connected with interactions occurring in the defect ensemble in the layer. The energetic approach is based on the analysis of the total energy density dependence on the number of MDs in the MD row. The approach allows to find critical parameters of a system (misfit strain and thickness of layer corresponding to the transition between the uniform and nonuniform MD distributions. Analyzing the conditions for surface dislocation sources initiation, the dynamic criterion is worked out. In such a model MD rows generate back stresses which lock the dislocation sources. A three-element defect reaction-diffusion scheme is proposed for the analysis of dislocation kinetics in the nanoscale layers. It is assumed that the defect ensemble consists of gliding, climbing and misfit dislocations. The existence of a critical layer thickness is predicted, above which temporal oscillations in the defect densities appear.