According to a report in the latest issue of Science, a research team led by the University of Tokyo in Japan has successfully fabricated a single-walled molybdenum disulfide (MoS₂) semiconductor nanotube with a diameter of only 1 nanometer, roughly one-hundred-thousandth the width of a human hair, using boron nitride (BN) nanotubes as a template. The structure is considered the world’s smallest semiconductor nanotube to date. The achievement not only confirms theoretical predictions made decades ago about the electronic properties of ultrathin materials, but also offers a new approach for the development of next-generation miniaturized electronic devices.
Carbon nanotubes once attracted broad attention for their excellent mechanical and electrical properties. However, slight differences in their atomic structure can significantly affect their conductivity, creating challenges for transistor applications. By contrast, MoS₂ is a naturally semiconducting material with broad potential in semiconductor electronic devices, high-sensitivity sensors, and quantum-scale physics research. As nanotube diameters shrink, however, structural stability and fabrication difficulty increase sharply. Producing ultrathin MoS₂ nanotubes with controlled structures has therefore remained a major challenge in materials science.
To overcome this limitation, the research team carried out chemical reactions within the narrow internal space of BN nanotubes, synthesizing single-walled MoS₂ nanotubes with a diameter of only 1 nanometer and a clearly defined atomic structure. The researchers said this confined space enabled the growth of ultrathin MoS₂ nanotubes that would otherwise be difficult to form, while also promoting ordered atomic arrangement and producing highly uniform materials with well-defined structures.
The study found that the band gap decreases as the nanotube diameter becomes smaller, confirming a theoretical prediction proposed 25 years ago.
Conventional nanotube fabrication methods typically produce multi-walled nanotubes with diameters larger than 10 nanometers, and their atomic structures are often difficult to precisely control. At the nanoscale, even extremely small structural differences can significantly affect material performance. Achieving atomic-level structural control is therefore highly significant for future device applications.
Existing semiconductor technologies face increasing difficulty in maintaining structural perfection as devices continue to shrink, with defects having a greater effect at smaller scales. Carbon nanotubes face similar challenges. MoS₂ nanotubes may offer advantages in dimensional control and atomic-structure consistency, providing a potential new route for building ultraminiaturized semiconductor channels.
The achievement remains some distance from practical application. The nanotubes currently produced are only several hundred nanometers long. The research team plans to extend their length to about 1 micrometer, or 1,000 nanometers, and to explore whether the same method can be used to fabricate other inorganic nanotube materials, including magnetic and superconducting materials.