Nanotubes are cylindrical structures formed by rolling two-dimensional sheets of atoms into nanoscale tubes, which convert a flat material into a one-dimensional one. Their properties are highly dependent on how the sheets are rolled. For example, carbon nanotubes can be either conducting or semiconducting based on their structural twist. Tungsten disulfide nanotubes, in contrast, consistently exhibit semiconducting properties due to their multi-layered Swiss-roll-like structure, making them particularly appealing for use in semiconducting devices.
Despite their potential, the application of tungsten disulfide nanotubes in devices has been hindered by a significant challenge: the nanotubes' orientations tend to be random, resulting in reduced carrier mobility and obscured direction-dependent properties. This random arrangement negates the unique optical and electronic behaviors inherent to single nanotubes when observed collectively.
Led by Professor Kazuhiro Yanagi, the research team addressed this challenge by employing a sapphire substrate with a carefully selected crystallographic plane to act as a growth template. They introduced tungsten and sulfur-containing gases to the substrate under precisely controlled conditions to enable chemical vapor deposition. This process led to the formation of multi-walled tungsten disulfide nanotubes that were uniformly aligned along a specific crystallographic direction - marking the first successful synthesis of such arrays.
The researchers further demonstrated that these aligned arrays retained the distinctive anisotropic properties of single nanotubes, particularly in their interactions with light. This breakthrough holds promise for developing real-world applications, including electronic and optoelectronic devices, that can fully exploit the exceptional properties of tungsten disulfide nanotubes.
Research Report:Synthesis of Arrayed Tungsten Disulfide Nanotubes