Atomic Scale Structure and Electronic Structure of Defects at Misfit Dislocations in CeO₂/MgO Heterostructure

Among the numerous functionalities of mismatched oxide heterostructures and thin films, one of their most promising energy applications is in solid oxide fuel cell (SOFC) electrolytes. Epitaxial growth of oxide thin films on substrates above critical thickness result in the formation of misfit dislocations. These functional extended defects influence key material properties of thin film SOFC electrolytes. Nevertheless, fundamental understanding of the atomic scale structure and electronic structure of misfit dislocations and their intricate interaction with mobile oxygen vacancies at functional oxide interfaces is lacking. In this work, first principles density functional theory was used to elucidate the atomic scale structure and electronic structure of misfit dislocations for experimentally observed epitaxy in CeO₂/MgO heterostructure. Rotation of CeO₂ thin film is uncovered as one potential mechanism eliminating the surface dipole, which results in experimentally observed epitaxy. In Gd-doped CeO₂ thin film, thermodynamic stability and electronic structure of oxygen vacancies in the neighborhood of misfit dislocations will be contrasted against their behavior in the bulk and at surfaces. Changes in the electronic density of states and interface electronic charge transfer due to defect formation in the vicinity of misfit dislocations and their impact on ionic transport will be discussed. Present results are instrumental in understanding the intricate interplay between misfit dislocations, dopants, and oxygen vacancies and their ultimate impact on ionic transport in thin film SOFC electrolytes.<br/><br/>We acknowledge support from NSF CAREER Award DMR-2042311.