At the University of Tokyo, researchers have synthesized semiconducting nanotubes so impossibly thin—just 1 nanometer wide—that they're 100,000 times thinner than a human hair. The breakthrough comes from a deceptively elegant approach: growing molybdenum disulfide inside protective tubes of boron nitride, creating what Associate Professor Yusuke Nakanishi describes as a coaxial structure ideal for the most advanced transistor architectures. Published in the journal Science, the work marks a watershed moment in materials science, proving that decades-old theoretical predictions about ultrafine materials actually hold true in practice.
For years, carbon nanotubes dominated the field and captured headlines. But molybdenum disulfide offers something carbon cannot: reliable semiconductor properties at the smallest scales. The distinction matters profoundly. Current silicon transistors face a fundamental problem as they shrink—defects become catastrophic, warping how the devices behave. Carbon nanotubes face a similar curse: even tiny structural variations can transform them from semiconductors into metals, making them unreliable for precise engineering. The new molybdenum disulfide nanotubes sidestep this trap entirely through atomic-level precision.
The innovation lies in the method itself. Conventional nanotube production struggles with diameters above 10 nanometers and often produces irregular, multiwalled structures with poorly controlled atomic arrangements. Nakanishi's team took a different path, synthesizing the molybdenum disulfide nanotubes inside the confined space of boron nitride tubes. This tight confinement does something counterintuitive: it actually helps. The narrow space constrains the molybdenum disulfide, preventing it from forming in its natural multiwalled configuration, and instead promotes the precise, single-walled atomic arrangements essential for engineered applications. They heated precursor materials in this confined space using chemical reactions, then verified the results using advanced electron microscopy and chemical mapping.
The findings solve a riddle that theoretical physicists posed more than 25 years ago. Nakanishi's measurements confirm their predictions: as the nanotubes shrink in diameter, their bandgap—the property that determines how they function as semiconductors—decreases predictably. This validation transforms theoretical possibility into practical foundation. "If the structure can be precisely controlled, the properties are more consistent, which is essential for reliable and reproducible transistor performance," Nakanishi explains. "Their biggest advantage is atomic-level structural control."
The applications hint at a future of miniaturized electronics. Molybdenum disulfide nanotubes could enable gate-all-around transistors, semiconductor electronics, and high-resolution sensing devices. Researchers also envision uses in quantum-scale physics research. Beyond semiconductors, the same technique might produce magnetic or superconducting nanotubes—entire new classes of atomically precise materials for applications yet unimagined.
Challenges remain before transistors built from these structures reach practical deployment. The current bottleneck is length: the nanotubes reach only several hundred nanometers, but applications require around 1 micrometer (1,000 nanometers) to be viable. Scaling up production while maintaining atomic precision will require methodical engineering. Still, the breakthrough itself is unambiguous. By moving beyond carbon and demonstrating atomic-scale control at the nanometer scale, Nakanishi's team has opened the door to a new era of materials science—one where the structure of matter itself becomes a controllable variable in device design.