Oxygen Vacancy Formation and Interface Charge Transfer at Misfit Dislocations in Gd-Doped CeO2/MgO Heterostructures

Among numerous functionalities of mismatched complex oxide thin films and heterostructures, their application as next-generation electrolytes in solid oxide fuel cells has shown remarkable promise. In thin-film oxide electrolytes, although misfit dislocations ubiquitous at interfaces play a critical role in ionic transport, fundamental understanding of their influence on oxygen vacancy formation and passage is nevertheless lacking. Herein, we report first-principles density functional theory calculations to elucidate the atomic and electronic structures of misfit dislocations in the CeO2/MgO heterostructure for the experimentally observed epitaxial relationship. Thermodynamic stability of the structure corroborates recent results demonstrating that the 45° rotation of the CeO2 thin film eliminates the surface dipole, resulting in experimentally observed epitaxy. The energetics and electronic structures of oxygen vacancy formation near gadolinium dopants at misfit dislocations are evaluated, which demonstrate complex tendencies as compared to the grain interior and surfaces of ceria. The interface charge transfer mechanism is studied for defect-free and defective interfaces. Since the atomic and electronic structures of misfit dislocations at complex oxide interfaces and their influence on interface charge transfer and oxygen vacancy defect formation have not been studied in the past, this work offers new opportunities to unravel the untapped potential of oxide heterostructures.