Annealing effect on dislocations in SrTiO3∕LaAlO3 heterostructures

Epitaxial SrTiO3 thin films were deposited on (001) LaAlO3 single crystals by pulsed laser deposition. The postannealing effect was studied by annealing the deposited films at 1100°C in O2 atmosphere for 4h. It was found that the postannealing treatment enhances the in-plane permittivity of the film. An analysis of the film lattice parameters from selected area electron diffraction and high-resolution electron microscopy shows a relaxation of the compressive strain by annealing. In addition, the density of threading dislocations is significantly reduced, and stacking faults with translation vector R=1∕2a⟨110⟩ resulting from the dissociation of threading dislocations are formed. Both structural and dielectric characterizations indicate that the enhancement of permittivity is mainly due to the relaxation of the misfit strain between the film and substrate. The reduction of the threading dislocation density by annealing may be beneficial to the reduction of the extrinsic dielectric loss in the film.