Point Contacts to Atomically Precise Graphene Nanoribbons

Bottom-up synthesized graphene nanoribbons (GNRs) are an emerging class of designer quantum materials that possess superior properties including atomically controlled uniformity and chemically tunable electronic properties. GNR-based devices are promising candidates for next-generation electronic, spintronic, and thermoelectric applications. However, a significant portion of the GNRs synthesized to date are unstable under ambient conditions and require protection from the environment. Here, we encapsulate 9-atom wide armchair GNRs (9-AGNRs) in Hexagonal Boron Nitride (h−BN) and contact them using metallic side contacts, leading to a point contact at the GNR/metal interface. At 9 K, quantum dot (QD) behavior with well-defined Coulomb diamonds is observed, with additional energies in the range of 20 to 400 meV. For increasing temperature, charge transport through the GNR film, occurring via a combination of temperature-activated hopping and nuclear tunneling, starts to dominate, with a crossover between QD transport and film transport occurring at around 100 K. At room temperature, our short-channel field-effect transistor devices exhibit on/off ratios as high as 3×10⁵. Overall, our work demonstrates that 9-AGNRs can be contacted while being encapsulated in h−BN. This enables a whole range of GNR candidates that are unstable under ambient conditions to be incorporated into electronic and spintronic devices.