Researchers Extend the Limits of Twistronics. Literally.
For Immediate Release
Researchers have shown it is possible to expand the field of twistronics – literally. The researchers have demonstrated a technique allowing them to fabricate oxide twistronic materials at much larger sizes, while also controlling the twist angles between materials that dictate their structural and electronic properties.
The field of twistronics examines how the angle between layers of two-dimensional (2D) materials affects their electronic properties.
“The field of twistronics was developed using 2D materials that are bonded by weak van der Waals forces,” says Ruijuan Xu, corresponding author of a paper on the work and an assistant professor of materials science and engineering at North Carolina State University. “Our work here demonstrates it is possible to use layers of oxide materials that are connected by strong chemical bonds – while precisely controlling the twist angle between crystalline oxide membranes.
“The strong interlayer bonding we found between oxide layers suggests there may be entirely new interfacial phenomena to explore,” adds Xu. “We’ve demonstrated the ability to control many of the materials characteristics – including phase structure and domain configuration – in ways that offer new routes for designing materials and devices tailored to specific applications.”
For this work, the researchers synthesized crystalline sodium niobate (NaNbO3) membranes and used photolithography to create a set of visual markers along the perimeter of each membrane. One NaNbO3 membrane was then lifted and placed on top of another NaNbO3 membrane. The researchers monitored the alignment of the visual markers during assembly to precisely control the relative twist angle between the two layers. Once the researchers established the desired angle, they performed a material-specific annealing process to establish strong chemical bonding between the layers.
“Scale matters for devices,” says Xu. “Because these crystalline membranes can be fabricated over large areas and transferred onto different supports, this approach provides a practical path toward twist-engineered oxide electronics.”
The researchers also used synchrotron X-ray diffraction techniques to capture what is actually happening at the interface between the two layers.
“We found that the bonds between the two layers are so strong that they are distorting the atomic structure of the material – creating a gradual rotation of the atomic lattice at the interface between the layers,” says Xu. “We also found changes to the phase structure of the material. It remains to be seen how this will affect material properties, but that’s something we are exploring.”
The researchers note that while this work was done using NaNbO3 as a model, the technique could be extended to other complex oxides.
“Our work demonstrates a technique for creating large-area oxide twistronic materials with controlled twist angles and a strong chemical bond between layers,” says Xu. “It’s an exciting time for oxide twistronics, with new opportunities to engineer complex oxides functionalities through twist.”
The paper, “Deterministic Fabrication of Large-Area, High-Crystallinity Oxide Moiré Superlattices,” is published in the journal ACS Nano. Co-lead authors of the paper are Reza Ghanbar, a Ph.D. student at NC State; and Eli Rodrigues, a graduate student at NC State who was involved with this work while still an undergraduate. The paper was co-authored by Konnor Koons, Kabelo Lebogang, Yiming Ding and Yueyin Wang, who are Ph.D. students at NC State; undergraduate Doug Barefoot; Yin Liu, an assistant professor of materials science and engineering at NC State; Young-Hoon Kim of Oak Ridge National Laboratory; Yan Li and Hua Zhou of Argonne National Laboratory; and Miaofang Chi of Oak Ridge National Laboratory and Duke University.
This work was done with support from the National Science Foundation under grants 2442399 and 2340751; the American Chemical Society Petroleum Research Fund under award 68244-DNI10; the Army Research Office under grant W911NF-25-1-0201; the Scialog grant #SA-QMI-2025-097c from Research Corporation for Science Advancement; and the U.S. Department of Energy.
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Note to Editors: The study abstract follows.
“Deterministic Fabrication of Large-Area, High-Crystallinity Oxide Moiré Superlattices”
Authors: Reza Ghanbari, Eli Rodrigues, Konnor Koons, Kabelo Lebogang, Yiming Ding, Doug Barefoot, Yueyin Wang, Yin Liu and Ruijuan Xu, North Carolina State University; Young-Hoon Kim, Oak Ridge National Laboratory; Yan Li and Hua Zhou, Argonne National Laboratory; and Miaofang Chi, Oak Ridge National Laboratory and Duke University
Published: July 13, ACS Nano
DOI: 10.1021/acsnano.6c04794
Abstract: Oxide twistronics extends moiré engineering beyond van der Waals materials, offering a promising platform for accessing emergent interfacial phenomena arising from the strong coupling of lattice, charge, and orbital degrees of freedom in complex oxides. However, deterministic fabrication of high-crystallinity oxide moiré superlattices over large lateral dimensions remains challenging due to the three-dimensional bonding network of oxides. Here, we demonstrate a scalable, generalized fabrication strategy that enables the formation of high-crystallinity oxide moiré superlattices with clean, chemically bonded interfaces and precisely controlled twist angles down to nominal values of 0.1º, achieving sub-degree twist-angle accuracy across large contiguous lateral dimensions approaching the millimeter scale. Using NaNbO3 as a model system, we show that the resulting interlayer coupling drives pronounced structural reconstruction that modifies both the phase structure and ferroelectric domain configuration. Synchrotron-based X-ray 3D reciprocal space mapping reveals the emergence of a single-phase state in twisted bilayers, in contrast to the mixed-phase structure observed in single-layer membranes prior to twist assembly. The structural signatures are further consistent with gradual lattice rotation distributed along the thickness direction that may accommodate interfacial shear strain, distinct from reconstruction observed in van der Waals moiré systems which primarily occurs through in-plane stacking rearrangement. This collective lattice response is correlated with twist-dependent nanoscale electromechanical modulations observed by piezoresponse force microscopy. These results establish a scalable materials platform for oxide twistronics and support the implementation of twist-engineered functionalities in practical, macroscale device architectures.
This post was originally published in NC State News.
