On October 29, another major research achievement from the University of Science and Technology of China (USTC) was published in Nature, the world’s top academic journal. A team from the Hefei National Research Center for Physical Sciences at the Microscale of USTC, together with collaborators, has successfully fabricated a new type of carbon nanoribbon. Experiments confirmed that this carbon material, merely around 0.9 nanometers wide, can conduct electricity like a metal, experimentally verifying a scientific prediction made nearly 30 years ago. The findings are expected to offer a new material option for developing future carbon-based chips.

Diamond and graphite are both made of carbon atoms yet possess vastly different properties, owing to the distinct arrangements of their carbon atoms. For example, carbon atoms in graphene are arranged into six-membered rings to form a honeycomb lattice. What would happen if these six-membered rings were replaced with five-membered and seven-membered rings?

As early as 1996, scientists theoretically predicted that such carbon structures might conduct electricity like metals. Known as carbon pentagon-heptagon structures, they are also termed “covalent metals” because carbon atoms are bonded via covalent bonds while exhibiting metallic electronic properties. Nevertheless, turning the theoretical prediction into reality has proven challenging, and this has remained a critical question awaiting experimental proof for nearly three decades.

In this work, the USTC-led research team overcame this challenge through stepwise on-surface synthesis. By tuning the synthesis route and selecting relatively stable molecules as precursors, followed by coupling, thermal rearrangement and other procedures, the team successfully produced carbon nanoribbons consisting solely of five-membered and seven-membered rings, resolving the long-standing difficulty in precisely fabricating such structures.

The team then experimentally characterized the electrical conductivity of the material. The results demonstrate that one variant of the carbon nanoribbon, roughly 0.9 nanometers in width, is metallic and enables efficient electron transport. Researchers also found that even for structures built from the same types of carbon rings, different atomic arrangements can lead to distinct electronic properties.

This study not only establishes a synthetic route for metallic carbon pentagon-heptagon nanoribbons, but also experimentally proves that efficient electron transport can be realized in sub-nanometer carbon skeletons by engineering the bonding configuration of carbon atoms. In the future, such materials hold potential as atomic-scale wires and interconnect components for carbon-based chips.

Source: Hefei Daily