Atomic-scale structure of misfit dislocations in CeO2/MgO heterostructures and thermodynamic stability of dopant–defect complexes at the heterointerface†
Complex oxide heterostructures and thin films have found applications across the board in some of the most advanced technologies, wherein the interfaces between the two mismatched oxides influence novel functionalities. It is imperative to comprehend the atomic-scale structure of misfit dislocations, which are ubiquitous in semi-coherent oxide heterostructures, and obtain a fundamental understanding of their interaction with point defects and dopants to predict and control their interface-governed properties. Here, we report atomistic simulations elucidating the atomic-scale structure of misfit dislocations in CeO2/MgO heterostructures. Our results demonstrate that the 45° rotation of CeO2 thin film is one of the potential fundamental mechanisms responsible for eliminating the surface dipole, leading to the experimentally observed mixed epitaxial relationship. We further report the thermodynamic stability of diverse dopant–defect complexes near misfit dislocations, wherein various scenarios for nearest neighbor bonding environments within the complexes are explored. Complex misfit dislocation structure, asymmetry, strain, and the availability of diverse nearest neighbor bonding environments between dopants and oxygen defects at the interface are accountable for a wide dispersion in energies within a given dopant–defect arrangement. As opposed to the bulk, the thermodynamic stability of oxygen vacancies is found to be sensitive to the dopant arrangement at the heterointerface. Extended stabilities of dopant–defect complexes at misfit dislocations reveal that they would influence ionic transport at heterointerfaces of fluorite-structured thin film electrolytes. Notably, the results herein offer a fundamental atomic-scale perspective of the intricate interplay between dopants, defects, and misfit dislocations at the heterointerfaces in mismatched oxide heterostructures.