Freestanding Perovskite Oxide Membranes: A New Playground for Novel Ferroic Properties and Applications

Abstract

Transition metal perovskite oxide membranes and their unique properties have attracted great attention recently and have been developed into one of the research frontiers in condensed matter physics and materials science. Free of constraint imposed by the underlying substrate, freestanding membranes exhibit extraordinary structural tunability and flexibility far exceeding the bulk materials and epitaxial films clamped on substrates, which substantially extends the explorable regime in the phase diagrams. Moreover, high‐quality oxide membranes, even down to a single unit cell, can be synthesized and stacked/integrated with any materials for novel artificial heterostructures and electronic applications. The exceptional structural tunability and stacking ability in oxide membranes provide new knobs to explore the spontaneous symmetry breaking in oxides, providing a fertile playground for emergent primary ferroic/multiferroic properties and electronic applications. Here, the recent progress is briefly reviewed and the promising outlook for future research in ferroic perovskite oxide membranes and their applications is discussed.

Unfolding the Challenges To Prepare Single Crystalline Complex Oxide Membranes by Solution Processing

“…On the other hand, the use of solvent-free chemical deposition techniques such as atomic layer deposition could be an attractive route toward all-chemical complex oxide membranes. Finally, further investigations on the interplay between strain gradient, phase distortion, and superflexibility in these complex oxides could offer many practical applications in sensors, memories, spintronics, electronic skins, and self-powered devices. − , These broad range of possibilities could also be extended to other piezoelectric, ferroelectric, and multiferroic perovskite oxides anticipating a rich playground for complex oxide freestanding membranes to create new functional materials.…”

“…Among the family of complex oxides, BiFeO 3 (BFO) is a multiferroic material that can also show photoinduced effects, being thus an attractive candidate to be used in next-generation electronic devices for applications in information storage, spintronics, sensors, actuators, and optoelectronics. − Until recently, the preparation of epitaxial complex oxide films, such as BFO, was restricted to specific substrates that can stand high-temperature treatments, most of them on rigid surfaces or with a small bending strain. − Therefore, the use of these substrates dramatically narrowed the potential applications of the epitaxial complex oxide films grown on top. The development of fabrication approaches that allow detaching the complex oxide from the growth substrate and freely handling it has opened a new ground of research. , It provides an unparalleled opportunity to manipulate these structures by applying extreme deformations, unlocking the system’s elastic response upon applying an external stimuli, − creating artificial architectures with emerging phenomena at the new interfaces, and integrating them with the platform of choice. − …”

“…The development of fabrication approaches that allow detaching the complex oxide from the growth substrate and freely handling it has opened a new ground of research. 12,13 It provides an unparalleled opportunity to manipulate these structures by applying extreme deformations, 14 unlocking the system's elastic response upon applying an external stimuli, 15−17 creating artificial architectures with emerging phenomena at the new interfaces, 18 and integrating them with the platform of choice. 19−23 Among the various existing approaches, the use of the watersoluble Sr 3 Al 2 O 6 (SAO) sacrificial layer and derived compositions is quite extended to ultimately obtain crystalline and single-oriented complex oxide membranes.…”

Interface Design beyond Epitaxy: Oxide Heterostructures Comprising Symmetry‐Forbidden Interfaces

“…Numerous research groups have fabricated and transferred single-crystalline membranes of 3D materials onto a variety of substrates. [22][23][24][25][26][27][28][29][30][31][32][33][34] This progress has even produced interfaces that are sufficiently clean for electronic applications. [35] Moreover, successful twisting and stacking of these membranes has been shown, where the overlaid lattices form moiré patterns.…”