Tokyo, Japan – Researchers at Tokyo Metropolitan University have successfully used nanowires of a transition metal chalcogenide to make atomically thin “nanoribons”. Bundles of nanowires were exposed to a gas of chalcogen atoms and heat which helped fuse the wires into narrow bands. Nanoribbons are highly sought after for sophisticated electronic devices; given the scalability of the method, the team hopes it will be widely used in the industrial production of advanced materials.

Materials science in the age of electronics is as demanding as it is revolutionary. As circuits become smaller, faster, and more energy efficient, scientists face the increasingly difficult challenge of controlling the atomic-level structure of the materials used in them. A promising avenue of research is the use of complex strands of material only a few atoms wide; one such structure is composed of transition metal chalcogenides, a combination of transition metals and chalcogens, atoms that share a column with oxygen on the periodic table. These atomically thin “nanowires” have properties specific to their one-dimensional structure and are highly sought after for sophisticated electronic devices. But what they have in detail, they lack in tunability. This is where “nanoribbons” come in, meaning narrow, atomically thin sheets. A fine control of their width, for example, leads to a controlled variation of their electronic and magnetic properties.

Many works have been applied to “build” nanoribbons from the bottom up. The problem, however, is that these methods are not very scalable. This is a problem for producing bulk quantities for commercial devices. Now, a team led by Dr. Hong En Lim and Associate Professor Yasumitsu Miyata of Tokyo Metropolitan University have developed a scalable way to assemble nanowires into nanoribbons. The team had already developed ways to produce nanowires in large quantities. By taking tungsten telluride nanowires, they created bundles of wires deposited on a flat substrate. These were exposed to vapors of different chalcogens like sulphur, selenium and tellurium. With a combination of heat and steam, the threads initially separated into the bundles were successfully woven into narrow, atomically thin “nanoribbons” with a characteristic zigzag structure. By adjusting the thickness of the original beams, they could even choose whether these ribbons were oriented parallel to the substrate or perpendicular to it, thanks to a competition between the ease of having edges or faces parallel to the lower surface. . Additionally, by adjusting the substrate on which the beams are placed, they could control whether the ribbons were randomly oriented or pointed in a single direction. Importantly, the method is scalable and can be applied to take synthesis from lab-scale fabrication of a few ribbons to bulk syntheses on large substrate areas.

The team was able to confirm that the ribbons they created had exotic electronic properties that are unique to their one-dimensional nature. This is not only a big step forward for materials science, but also a tangible step towards the mass production of nanoribbons in advanced electronics, optoelectronics and catalysts.

This work was supported by numbers JST CREST Grant JPMJCR16F3, JPMJCR17I5 and JPMJCR20B1 and numbers JSPS KAKENHI Grant JP18H01832, JP19K15383, JP19K15393, JP19K22127, JP20H02572, JP20H02605, JP20H05189, JP20H05664, JP20H05867, JP20H05870, JP20J21812, JP21H05232, JP21H05234, JP21H05236 and JP21K14498.

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