On-surface synthesis of graphene nanoribbons could advance quantum devices

image: Scientists synthesized graphene nanoribbons, shown in yellow, on a titanium dioxide substrate, in blue. The lighter ends of the ribbon show magnetic states. The inset drawing shows how the ends have up and down spin, suitable for creating qubits. view more 

Credit: Credit: ORNL, U.S. Dept. of Energy

An international multi-institution team of scientists has synthesized graphene nanoribbons - ultrathin strips of carbon atoms - on a titanium dioxide surface using an atomically precise method that removes a barrier for custom-designed carbon nanostructures required for quantum information sciences.

Graphene is composed of single-atom-thick layers of carbon taking on ultralight, conductive and extremely strong mechanical characteristics. The popularly studied material holds promise to transform electronics and information science because of its highly tunable electronic, optical and transport properties.

When fashioned into nanoribbons, graphene could be applied in nanoscale devices; however, the lack of atomic-scale precision in using current state-of-the-art "top-down" synthetic methods -- cutting a graphene sheet into atom-narrow strips - stymie graphene's practical use.

Researchers developed a "bottom-up" approach -- building the graphene nanoribbon directly at the atomic level in a way that it can be used in specific applications, which was conceived and realized at the Center for Nanophase Materials Sciences, or CNMS, located at the Department of Energy's Oak Ridge National Laboratory.

This absolute precision method helped to retain the prized properties of graphene monolayers as the segments of graphene get smaller and smaller. Just one or two atoms difference in width can change the properties of the system dramatically, turning a semiconducting ribbon into a metallic ribbon. The team's results were