Scientists from the RIKEN Center for Emergent Matter Science and their collaborators have developed a technique for building three-dimensional nanoscale structures directly from single-crystal materials. The method relies on a focused ion beam tool that can precisely remove material at extremely small scales. Using this approach, the team carved tiny spiral structures from a topological magnetic crystal made of cobalt, tin, and sulfur with the chemical formula Co3Dream2WITH2. Tests have shown that these structures behave like switchable diodes, meaning that electrical current flows in one direction more easily than the other.
Electronics built with complex three-dimensional shapes could be smaller, more efficient and more powerful than today’s flat devices. Despite this potential, researchers have had limited ways to create such structures. Existing manufacturing methods often limit which materials can be used and can compromise the quality of the final device.
Precise cutting with focused ion beams
In a new study published in Nature Nanotechnologythe researchers solved these problems by using a focused ion beam capable of cutting with submicron precision. This level of control allows, in principle, the creation of three-dimensional devices from almost any crystalline material. The process resembles sculpting, where material is carefully removed from a solid block until the desired form is achieved.
To demonstrate the method’s capabilities, the team fabricated helical nanodevices from a magnetic Co crystal3Dream2WITH2. Based on the known properties of this material, they expected that the twisted geometry would create a special diode effect called non-reciprocal electrical transport, controlled by the nanoscale chiral shape. Experiments confirmed this prediction. Electric current flowed more easily in one direction and the effect could be reversed by changing the magnetization or switching the handedness of the helix. The researchers also observed the reverse interaction, where strong electrical pulses could reverse the structure’s magnetization. Diodes are fundamental components of modern electronics and are used in AC/DC conversion, signal processing and LED devices.
How Shape controls the movement of electrons
By comparing helices of different sizes and measuring their behavior at different temperatures, the researchers traced the diode effect to the uneven scattering of electrons along the curved chiral walls of the device. These findings show that the physical shape of a component can directly affect how electricity travels through it. The results suggest that the geometry itself can be used as a design tool to enable low-power, shape-engineered components for future memory, logic and sensing technologies.
According to Max Birch, first author of the study, “By treating the geometry as a source of symmetry breaking on par with the intrinsic material properties, we can create electrical non-reciprocity at the device level. Our newly developed ion beam nanosculpting method opens up a wide range of studies on how three-dimensional and curved device geometries can be used to realize new electronic functions.”
Yoshinori Tokura, who leads the research group, added: “More broadly, this approach enables device designs that combine topological or strongly correlated electronic states with designed curvature in the ballistic or hydrodynamic transport regime. The convergence of materials physics and nanofabrication points to functional device architectures with potential impact on memory, logic and sensing technologies.”
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