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.