Theory of the birefringence due to dislocations in single crystal CVD diamond

Single crystal diamond grown by chemical vapour deposition (CVD) often exhibits strain induced birefringence arising from bundles of edge dislocations lying almost parallel to the [001] growth axis. The birefringent pattern changes when the crossed-polarizers are rotated with respect to the underlying lattice. For polarizers parallel to ⟨110⟩ directions, the birefringence pattern consists of four bright petals with dark arms along ⟨110⟩. For polarizers parallel to ⟨100⟩, the birefringence pattern consists of eight petals of weaker intensity with dark arms along ⟨110⟩ and ⟨100⟩ directions. We evaluate the birefringence intensity by using isotropic elasticity theory and find that these patterns can be explained by a specific dislocation arrangement which is consistent with x-ray topographic studies.