Current effect on suspended graphene nanoribbon studied using in-situ transmission electron microscopy

Graphene nanoribbons (GNRs) are expected in nanodevices and sensors but are degraded by contaminants that adsorb firmly on the surface during the transfer and lithography processes. Current annealing appears to be the most appropriate cleaning method, but its effects have not been quantitatively clarified. To this end, the cleaning processes of suspended monolayer GNRs were observed by in situ transmission electron microscopy. The gradual cleaning processes, which were successfully observed by improving the contact resistance at graphene-metal interface, showed that the GNRs was cleaned on the atomic scale in the current density range of 2.0-5.0 x 10(12) A/m(2). The corresponding temperature was estimated to be similar to 700 K by finite element method. To be surprised, clean monolayer and bilayer GNRs withstood current densities of 5.1 x 10(12) A/m(2) and 1.7 x 10(13) A/ m(2) (current-carrying capacities), respectively, which values were approximately three orders of magnitude higher than those of typical metals. The higher current-carrying capacity of bilayer GNR can be attributed to the formation of closed edges. This study shows that the electrical current is effective for cleaning GNR and boosting the current-carrying capacity.