Peculiarities of dislocation structure at surface of deformed crystals

An experimental study of the distribution of edge and screw dislocation components in deformed LiF crystals at external surface parallel to Burgers vector of mobile dislocations was performed. At the surface we observed a layer with low density of edge and screw dislocations compared to the dislocation density in the bulk. The thickness of this layer was tens of microns. The experimental results are explained on the basis of analysis of dislocation structure evolution at surface layers during the plastic deformation.