Direct observations of jog formation and drag caused by screw-screw dislocation interaction

During deformation of crystalline materials, moving dislocations interact with one another, which severely controls their mechanical responses. In particular, intersections between screw dislocations have been proposed to significantly decrease the mobility of screw dislocations due to the formation of jogs. However, the detailed intersection processes and the motion of jogged screw dislocations have not been well characterized for many years. Here, we directly observe screw-screw dislocation intersections, jog formation and jog dragging/gliding in SrTiO 3 via in situ nanoindentation inside a transmission electron microscope. Our in situ observations clearly show that screw-screw dislocation intersections and the consequent jog drag effectively limit dislocation mobility. It was found that jogs on a screw dislocation can be swept out along the dislocation line if an inhomogeneous stress distribution is applied along the dislocation line. The present findings indicate that the stress distribution along the dislocation line crucially affects jogged screw dislocation mobility.