The importance of edges in reactive ion etched graphene nanodevices

Patterned graphene nanodevices are promising candidates for nano-and quantum-electronics. Low temperature electronic transport in reactive ion etched graphene nanodevices is typically governed by charge localization manifesting itself in the appearance of Coulomb blockade. The disorder originating from non-perfect graphene edges was identified as being the dominant reason for the stochastic charge localization in graphene nanoribbons. It was found that electrons can localize along the edges on length scales much longer than the physical disorder length. Such states localized along the edge can even leak out of the nanoribbon into adjacent wide graphene leads suggesting that a possibly existing confinement gap is not required to explain transport properties of etched graphene nanodevices. These insights are then used to improve the understanding of transport in graphene quantum dots where Coulomb blockade is typically more regular than in nanoribbons. It is shown that non-overlapping Coulomb diamonds can be observed even in a regime where three states of localized charge need to be passed in series by an electron traveling from source to drain contact. This counter-intuitive observation is explained by higher order co-tunneling through the localized states in the nanoribbons connecting the graphene dot to the leads. [GRAPHICS] (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim