Atomic-scale imaging of heterointerface and planar faults in epitaxial (Pr, Sr)2CoO4 films on SrTiO3 (0 0 1) substrates

Abstract

Epitaxial c-axis-oriented (Pr, Sr)2CoO4 thin films have been successfully prepared on single-crystalline SrTiO3 (0 0 1) substrates by pulsed laser deposition technique. By using advanced imaging techniques and energy-dispersive X-ray spectroscopy mapping, the atomic-scale structural properties of interface and planar faults have been investigated in the (Pr, Sr)2CoO4/SrTiO3 (0 0 1) system. Two types of interface structure have been characterized in the heterostructure. The coalescence of different types of interface results in the formation of interfacial dislocations and nano-scale twin lamellae in the films, which in accompany with misfit dislocation contribute to strain relaxation in the heterostructure. In addition, the perovskite (Pr, Sr)CoO3 slabs in the films lead to the formation of complex planar faults, which disturb the square-lattice CoO2 sheets of the (Pr, Sr)2CoO4 films. The findings obtained in the (Pr, Sr)2CoO4/SrTiO3 (0 0 1) system could be applicable to other Ruddlesden-Popper phases in the form of thin films.