Interface Engineering and Emergent Phenomena in Oxide Heterostructures

Abstract

Complex oxide interfaces have mesmerized the scientific community in the last decade due to the possibility of creating tunable novel multifunctionalities, which are possible owing to the strong interaction among charge, spin, orbital, and structural degrees of freedom. Artificial interfacial modifications, which include defects, formal polarization, structural symmetry breaking, and interlayer interaction, have led to novel properties in various complex oxide heterostructures. These emergent phenomena not only serve as a platform for investigating strong electronic correlations in low-dimensional systems but also provide potentials for exploring next-generation electronic devices with high functionality. Herein, some recently developed strategies in engineering functional oxide interfaces and their emergent properties are reviewed.

Beyond Coherent Oxide Heterostructures: Atomic‐Scale Structure of Misfit Dislocations

“…In the majority of the cases, the final product (heterostructure) exhibits superior properties, and in some instances even emergent properties in comparison to the individual components. [1][2][3] Interfaces are critical in complex oxide heterostructures as they DOI: 10.1002/adts.201900078 offer diverse modes to introduce nonhomogeneity in the material. This nonhomogeneity at the interface is often manifested in considerable modification of thermal, electrical, transport, and mechanical properties of the heterostructure.…”

“…[1,[4][5][6][7][8][9][10][11]21,22] Furthermore, substantial experimental efforts have been dedicated to investigating the role of oxide interfaces, and there is significant progress in elucidating novel phenomena in oxide heterostructures. [1][2][3]8,35] For instance, observed novel phenomena include superionic conductivity, superconductivity, high electronic mobility, magnetoelectric coupling, quantum transport effect, ferroelectricity, metal-insulator transition, enhanced thermal transport, enhanced radiation resistance, lattice-electron coupling, and spin-orbit coupling. [1][2][3]6,8,19,22,35] Nevertheless, fundamental understanding pertaining to the atomic-scale processes and mechanisms responsible for the origin of the aforementioned emergent phenomena in oxide heterostructures is not easily accessible from experiments due to, for example, buried interfaces encountered during synthesis.…”

“…[1][2][3]8,35] For instance, observed novel phenomena include superionic conductivity, superconductivity, high electronic mobility, magnetoelectric coupling, quantum transport effect, ferroelectricity, metal-insulator transition, enhanced thermal transport, enhanced radiation resistance, lattice-electron coupling, and spin-orbit coupling. [1][2][3]6,8,19,22,35] Nevertheless, fundamental understanding pertaining to the atomic-scale processes and mechanisms responsible for the origin of the aforementioned emergent phenomena in oxide heterostructures is not easily accessible from experiments due to, for example, buried interfaces encountered during synthesis. In addition, it is conceivable that there is synergy or competition between various atomistic mechanisms that contribute to the emergence of novel phenomena at oxide interfaces, which is not trivial to decouple experimentally.…”

Conducting LaVO3/SrTiO3 Interface: Is Cationic Stoichiometry Mandatory?

“…A marked difference between the LaO/TiO 2 and AlO 2 /SrO interfaces is that the insulating nature of the later suggests that oxygen vacancies and cation intermixing at the interface cannot be the sole reason for the interfacial conductivity. Experimental evidences have been gradually converging towards the conclusion that the electronic reconstruction is the prime mechanism for the appearance of conducting states at the interface . At the same time, it was appreciated that the atomic reconstruction, which is known from the studies of semiconductor interfaces, can also be in play and compensate for the formation of the interfacial electric field without providing charge carriers to the interface .…”

“…Experimental evidences have been gradually converging towards the conclusion that the electronic reconstruction is the prime mechanism for the appearance of conducting states at the interface. [1,[22][23][24][25] At the same time, it was appreciated that the atomic reconstruction, which is known from the studies of semiconductor interfaces, can also be in play and compensate for the formation of the interfacial electric field without providing charge carriers to the interface. [26] As the result of two competing reconstruction processes the conducting properties of LAO-STO interface depend on the LAO film stoichiometry.…”