Abstract: To get the screw dislocation motion characteristic in the growing process of lattice mismatched heterostructures, a pair of screw dislocations is introduced in a full periodic Si crystal via dislocation dipole modeling. The screw dislocation motion velocity and cross\|slip versus the shear stress applied by Parrinello\|Rahman method are investigated by utilizing molecular dynamics simulation technique. In addition, how the motion of screw dislocation is affected by a vacancy defect is investigated. It is found that a ring\|shaped hexagonal vacancy located in the dislocation slip plane can facilitate the motion of the screw dislocation. The motion velocity is increased in comparison with that of the model without vacancy defect. The screw dislocation can eventually stride over the ring-shaped hexagonal vacancy during cross-slip, preventing from being pinned. These results reveal the basic mechanism of LT-Si technology, i.e., a large amount of vacancy defects located in Si layer can eventually reduce the dislocation density due to the dislocation motion characteristics.

Key words: computational physics, dislocation motion, molecular dynamics, vacancy defect, dislocation velocity, Si crystal