Formation of dislocations via misfit strain across interfaces in epitaxial BaTiOand SrIrOheterostructures.

Dislocations often occur in thin films with large misfit strain as a result of strain energy accumulation and can drastically change the film properties. Here the structure and dislocations in oxide heterostructures with large misfit strain are investigated on atomic scale. When grown on SrTiO(001), the dislocations in both the monolithic BaTiOthin film and its superlattices with SrIrOappear above a critical thickness around 6 nm. The edge component of the dislocations is seen in both cases with the Burgers vector of⟨100⟩. However, compared to monolithic BaTiO, the dislocation density is slightly lower in BaTiO/SrIrOsuperlattices. In the superlattice, when considering the SrTiOlattice constant as the reference, BaTiOhas a larger misfit strain comparing with SrIrO. It is found that in both cases, the formation of dislocation is only affected by the critical thickness of the film with larger lattice misfit (BaTiO), regardless of the existence of a strong octahedral tilt/rotation mismatch at BaTiO/SrIrOinterface. Our findings suggest that it is possible to control the position of dislocations, an important step toward defect engineering.