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For more than 25 years, physicists have predicted that shrinking certain semiconductor nanotubes to extreme dimensions would fundamentally alter their electronic behaviour. The problem was proving it. Structures at this scale are notoriously difficult to manufacture because they become unstable long before reaching the sizes required for experimental validation. Researchers at the University of Tokyo have now overcome that challenge by creating atomically precise molybdenum disulphide nanotubes measuring just one nanometre in diameter, approximately 100,000 times thinner than a human hair. Beyond establishing one of the world’s smallest semiconducting nanotubes, the achievement resolves a long-standing theoretical question about how electronic properties change at the nanoscale and provides a new platform for designing future ultra-miniaturised electronic components.
How ultrathin molybdenum disulphide nanotubes could transform future transistors and quantum devices
Nanotubes have attracted scientific interest since the early 1990s because their cylindrical atomic structures can exhibit unusual electrical, optical and mechanical properties. While carbon nanotubes became the dominant focus of research, scientists also predicted that inorganic semiconductor nanotubes could offer advantages for future electronics if their atomic structures could be precisely controlled. This was followed in 1995 by the successful high-rate, gas-phase growth of MoS2 nested inorganic fullerenes and nanotubes.
Advancements in functional properties
As the field progressed, research shifted toward understanding the unique physical properties of these materials: Superconductivity and Photovoltaics: Investigations into related chiral nanotubes led to the discovery of superconductivity in 2017 and an enhanced intrinsic photovoltaic effect in tungsten disulfide nanotubes in 2019Theoretical Predictions: Theoretical studies, such as those conducted in 2000 and 2002, predicted that the electronic properties and stability of MoS2 nanotubes would change significantly as their diameters decreased, specifically predicting that bandgaps would shrink with decreasing diameterThe research ‘Confined growth of armchair MoS2 nanotubes at the 1-nm limit’ marks that the challenge lies in size. Conventional fabrication methods generally produce nanotubes larger than 10 nanometres in diameter, often with multiple walls and structural irregularities. Theoretical models developed more than two decades ago suggested that much smaller single-walled nanotubes should exhibit measurable changes in their electronic bandgap, a property that determines how semiconductors conduct electricity. Until now, those predictions remained largely untested.According to Associate Professor Yusuke Nakanishi, Department of Advanced Materials Science in Kashiwa, of the University of Tokyo:”We achieved the synthesis of atomically precise semiconducting nanotubes with nanometer diameters. These precise nanotubes are identified as an ideal platform for nanoscale transistor channels.”The team’s measurements demonstrated that the bandgap decreases as the nanotube diameter becomes smaller, directly confirming theoretical predictions proposed more than a quarter of a century ago.
Building a stable nanotube only one nanometre wide
To achieve the breakthrough, researchers used boron nitride nanotubes as protective outer templates. Within these confined nanoscale spaces, molybdenum disulphide (MoS₂) atoms assembled into highly ordered single-walled nanotubes approximately one nanometre across.Historically, such small nanotubes were considered unstable or inaccessible due to the extreme strain caused by their high curvature. Researchers achieved stability by using spatially confined reactions inside insulating boron nitride (BN) nanotubes.Advanced electron microscopy and chemical mapping confirmed the structures and revealed exceptionally well-defined atomic arrangements. The surrounding boron nitride acted as a stabilising shell, allowing the ultrathin semiconductor nanotubes to form without collapsing.The resulting structures differ significantly from many existing nanotube systems. Rather than relying on multiple concentric walls or support materials inside the tube, the new architecture preserves a clean semiconducting channel with atomic-level precision.Yusuke Nakanishi, the lead and corresponding author, explained:”Their biggest advantage is atomic-level structural control. This specific architecture is viewed as a promising path toward creating truly nanoscale transistor channels.”
Why the discovery matters for future electronics
As silicon transistors continue approaching physical scaling limits, engineers are exploring alternative materials capable of maintaining predictable behaviour at extremely small dimensions. Tiny structural imperfections increasingly affect performance as devices shrink, creating one of the major obstacles facing future semiconductor technology.The newly developed nanotubes offer a potential solution because their atomic structure can be controlled with far greater precision than conventional semiconductor channels. The researchers believe the coaxial arrangement, in which a semiconducting MoS₂ nanotube is surrounded by an insulating boron nitride nanotube, could eventually be useful for gate-all-around transistor architectures, one of the most advanced designs currently being pursued by the semiconductor industry.Although practical devices remain years away, the work establishes a new pathway for constructing semiconducting nanotubes with predictable electronic properties. The approach may also be extended to magnetic, superconducting and other inorganic materials, potentially broadening nanotube science far beyond carbon-based systems.More importantly, the achievement closes a chapter that began with theoretical calculations more than 25 years ago. What was once a prediction confined to mathematical models can now be measured directly within a nanotube only one billionth of a metre wide. Go to Source
