Carbon Pentaheptite Nanoribbon Built to Defy Graphene Limits
Theorists predicted a flat carbon sheet built from pentagons and heptagons would behave like a metal back in 1996, but making it remained out of reach until chemists at the University of Science and Technology of China built a narrow ribbon with that exact structure and measured the current flowing through it. Their study in Nature reports that the resulting carbon nanoribbon carries electrons with little scattering, close to the limit of a single quantum channel.
Synthesizing Carbon Chains Directly on Silver Surfaces
Previous manufacturing roadblocks were sidestepped through surface-based, step-by-step synthesis directed by Wang Bing and Fan Qitang alongside their team at the Hefei National Research Center for Physical Sciences at the Microscale. Heat-driven reactions on silver first produced chains of paired five-membered rings before joining those chains side by side to create the ribbons, according to the study in Nature. Two distinct variants emerged from the process, sharing the same core structure while their carbon chains lined up differently along their edges.
Measuring Quantum Conduction Across Nanoscale Circuits
To test conduction, the research team attached the tip of a scanning tunneling microscope to one end of a ribbon and lifted it to form a tiny circuit between the tip and the silver below. Operating under a 10-millivolt bias at low temperature, the initial variant—named CPHN 1—achieved a conductance measuring approximately 0.9 of the conductance quantum, which serves as the fundamental unit for a single ideal electron channel. That value barely changed as the lifted length grew to about 4 nanometres. A sister ribbon, CPHN 2, behaved very differently with a conductance roughly two orders of magnitude lower, proving that a change in edge arrangement alone turned a metal into a semiconductor.
Integrating Atomic Wires into Future Computer Chips
Chipmakers want ever thinner interconnects, but traditional metal wires struggle at atomic scales while metallic carbon nanotubes remain difficult to sort and place. Atomically defined ribbons offer an attractive alternative, and a research briefing published with the paper notes that the method links previously inaccessible chains. Practical devices remain distant because the ribbons currently grow on silver and would have to move onto chips.
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