The transformation of dislocation cores from the shuffle to the glide set of {111} glide planes in Si is examined in this work. The transformation is thermally activated and is favored by a resolved shear stress which applies no force on the original perfect shuffle dislocation. A resolved shear stress driving dislocation motion in the glide plane is not observed to promote the transition. The stress-dependent activation energy for the described shuffle-glide transformation mechanism is evaluated using a statistical analysis. It is observed that the transformation is not associated with an intermediate metastable state, as has been previously suggested in the literature.
Nucleation of dislocation loops from sharp corners playing the role of stress concentrators located on the surface of Si 1Àx Ge x strained layers is studied. The surface is of {100} type and the concentrator is oriented such as to increase the applied resolved shear stress in one of the {111} glide planes. The mean stress in the structure is controlled through the boundary conditions, independent of the Ge concentration. Shuffle dislocations are considered throughout, as appropriate for low temperature-high stress conditions. The effect of Ge atoms located in the glide plane, in the vicinity of the glide plane and at larger distances is studied separately. It is observed that Ge located in the glide plane leads to the reduction of the activation energy for dislocation nucleation. The activation volume in presence of Ge is identical to that in pure Si. Ge located in {111} planes three interplanar distances away from the active glide plane has little effect on nucleation parameters. The far-field Ge contributes through the compressive normal stress it produces and leads to a slight reduction of the activation energy for shuffle dislocation nucleation.
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