Edge Contacts to Atomically Precise Graphene Nanoribbons

Bottom-up-synthesizedgraphene nanoribbons (GNRs) arean emergingclass of designer quantum materials that possess superior properties,including atomically controlled uniformity and chemically tunableelectronic properties. GNR-based devices are promising candidatesfor next-generation electronic, spintronic, and thermoelectric applications.However, due to their extremely small size, making electrical contactwith GNRs remains a major challenge. Currently, the most commonlyused methods are top metallic electrodes and bottom graphene electrodes,but for both, the contact resistance is expected to scale with overlaparea. Here, we develop metallic edge contacts to contact nine-atom-widearmchair GNRs (9-AGNRs) after encapsulation in hexagonal boron-nitride(h-BN), resulting in ultrashort contact lengths.We find that charge transport in our devices occurs via two differentmechanisms: at low temperatures (9 K), charges flow through singleGNRs, resulting in quantum dot (QD) behavior with well-defined Coulombdiamonds (CDs), with addition energies in the range of 16 to 400 meV.For temperatures above 100 K, a combination of temperature-activatedhopping and polaron-assisted tunneling takes over, with charges beingable to flow through a network of 9-AGNRs across distances significantlyexceeding the length of individual GNRs. At room temperature, ourshort-channel field-effect transistor devices exhibit on/off ratiosas high as 3 x 10(5) with on-state current up to 50nA at 0.2 V. Moreover, we find that the contact performance of ouredge-contact devices is comparable to that of top/bottom contact geometriesbut with a significantly reduced footprint. Overall, our work demonstratesthat 9-AGNRs can be contacted at their ends in ultra-short-channelFET devices while being encapsulated in h-BN.ISSN:1936-0851ISSN:1936-086