Researchers have developed a way to make twisted oxide materials over much larger areas while maintaining precise control over how their layers are rotated. The advance could help move twistronics closer to practical electronic devices by giving scientists greater control over both the scale and internal structure of these materials.
Twistronics explores how rotating one layer of a two-dimensional (2D) material relative to another can change the material's electronic behavior. Until now, much of the field has focused on extremely thin materials held together by relatively weak forces.
"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."
Building Large Twisted Oxide Membranes
To demonstrate the technique, the team produced crystalline sodium niobate (NaNbO3) membranes. Using photolithography, they added visual reference markers around the edges of each membrane.
The researchers then lifted one NaNbO3 membrane and positioned it on top of a second membrane. By watching how the reference markers lined up during assembly, they could carefully set the rotation angle between the two layers.
After reaching the desired orientation, the team used an annealing process designed specifically for the material. This treatment formed strong chemical bonds between the stacked membranes.
"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."
Strong Bonds Reshape the Atomic Lattice
The scientists used synchrotron X-ray diffraction to examine the boundary where the two oxide layers meet. The measurements revealed that the strong bonding between the membranes does more than simply hold them together.
"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."
These structural changes could eventually influence the material's electronic and physical behavior, although further research will be needed to determine their full effects.
A Broader Platform for Oxide Electronics
The experiment used NaNbO3 as a model system, but the researchers say the same method may also work with other complex oxide materials.
"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 oxide 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.
