Dislocation densities in copper single crystals after thermal treatment

Copper crystals of high purity and doped with nickel were subjected to a long time thermal treatment at 1050°C, in order to reduce the as-grown dislocation density of about 10⁷ cm⁻². A dissolution of the dislocations during their motion to the crystal surface was observed. Regions of different dislocation densities arose. Finally the crystals exhibited constant dislocation densities of 10² cm⁻². Such a perfection or a better one of the crystals is reached only by a long time treatment, since the dislocation velocity without external stresses cannot exceed 1 · 10⁻⁷ cm · s⁻¹ in copper single crystals of high purity.