Precision-grown nanotubes for next-gen electronics

Researchers in Japan have developed highly uniform semiconducting nanotubes with diameters of approximately 1 nanometre. By growing molybdenum disulfide (MoS₂) within protective boron nitride nanotube templates, the team, including researchers from the University of Tokyo, produced stable, well-defined structures at a scale where precise synthesis and structural integrity are challenging to achieve. The findings validate longstanding theoretical predictions about the behaviour of ultrafine nanotube materials and could open new opportunities for further miniaturisation of electronic devices.

Molybdenum disulfide nanotubes, though still experimental in nature, could be suitable for applications in semiconductor electronics, high-resolution sensing and quantum-scale physics research.

“We achieved the synthesis of atomically precise semiconducting nanotubes with nanometre diameters. The coaxial structure, where a semiconducting MoS₂ nanotube is surrounded by an insulating boron nitride (BN) nanotube, is attractive for gate-all-around transistors, one of the most advanced transistor architectures,” said Associate Professor Yusuke Nakanishi from the University of Tokyo. “Our paper demonstrates a way for structural control of inorganic semiconducting nanotubes at the atomic scale. We experimentally demonstrated that the bandgap (related to how materials work as semiconductors) of the nanotubes decreases as their diameters become smaller, in agreement with theoretical predictions proposed more than a quarter century ago.”

Conventional methods to produce nanotubes are usually limited to diameters above 10 nanometres, multi-walled concentric tubes, and poorly controlled or irregular atomic structures. Nakanishi and his team synthesised 1-nanometre-wide, single-walled MoS₂ nanotubes, with well-defined atomic structures. The researchers used chemical reactions inside the narrow space of BN nanotubes. The confined space constrains the MoS₂ nanotubes, which would otherwise be difficult to form, and promotes well-defined atomic arrangements, essential for engineered applications.

“In nanotubes, even small structural differences can strongly affect their properties. If the structure can be precisely controlled, the properties are more consistent, which is essential for reliable and reproducible transistor performance. Their biggest advantage is atomic-level structural control,” Nakanishi said. “Current silicon transistors are typically made by etching bulk silicon, but it’s increasingly difficult to keep their structures perfect at smaller sizes, where defects have a big impact. Carbon nanotubes also face a challenge for transistor applications, since even tiny structural differences can change how they behave, including whether they act more like metals or semiconductors. Our nanotubes could offer a more reliable way to build ultra-small semiconductor channels with consistent properties.”

The researchers next aim to increase nanotube lengths from several hundred nanometres to approximately 1 micrometre (which is one-thousandth of a millimetre) and extend the approach to other inorganic nanotube materials, including magnetic and superconducting systems. They hope the work will broaden nanotube research beyond carbon-based materials and enable new classes of atomically precise structures for sensing and nanoelectronics.

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