Electrically tunable localized states in sub-band of bilayer graphene nanoribbon

Multiple sub-band transport in bilayer graphene nanoribbons (GNRs) with localized charge states has not been experimentally investigated owing to the difficulty of accessing into the upper sub-band. In this letter, we utilize current annealing to heavily p-dope graphene from a capping hydrogen-silsesquioxane layer. As a result, Fermi energy can be tuned into the upper sub-valence band with reasonably small gate voltage. Owing to the localized charge states, quantum dot-like characteristics are measured in bilayer GNRs, as a result of the tunnelling transport of holes in the upper sub-band through these charge puddles. In contrast to monolayer GNRs, this phenomenon appears in a considerable conductive regime since the carrier transport in the lower sub-band is still diffusive. Moreover, by electrically tuning the Fermi energy, the localized charge puddles in the upper sub-band can be resized and isolated from each other.