Anomalous magnetotransport in nanostructured graphene

The magneto-transport properties of nanostructured graphene were investigated in comparison with bulk-size graphene. A ribbon-shaped nanographene with a width of 200 nm and a thickness of five graphene layers was fabricated using oxygen plasma etching and electron beam lithography with a removable nano-patterned mask for mechanically exfoliated graphene. The gate voltage dependence of the conductivity showed a significant effect of the extrinsic doping on the as-prepared nanographene, which originates from the adsorbed species strongly bound to the chemically active edge site. After the cleaning process, two series of Shubnikov–de Haas oscillations were observed in magnetoresistance, which reveals the coexistence of linear and parabolic bands, being consistent with the sample thickness of five layers. The gate voltage dependence of the frequency of the oscillation for the linear band exhibits an anomalous maximum around the Dirac point for the ribbon-shaped nanographene sample, suggesting the presence of the trapped orbital modified by the local doping effect at the edge.