From Diffusive to Ballistic Transport in Etched Graphene Constrictions and Nanoribbons

Graphene nanoribbons and constrictions are envisaged as fundamental components of future carbon‐based nanoelectronic and spintronic devices. At nanoscale, electronic effects in these devices depend heavily on the dimensions of the active channel and the nature of edges. Hence, controlling both these parameters is crucial to understand the physics in such systems. This review is about the recent progress in the fabrication of graphene nanoribbons and constrictions in terms of low temperature quantum transport. In particular, recent advancements using encapsulated graphene allowing for quantized conductance and future experiments towards exploring spin effects in these devices are presented. The influence of charge carrier inhomogeneity and the important length scales which play a crucial role for transport in high quality samples are also discussed. Recent technological developments allow the fabrication of etched high‐quality graphene nanoconstrictions and nanoribbons that exhibit ballistic transport and quantized conductance. The transport through such devices depends crucially on the nature of the edges and the localized edge states. By incorporating local top gates, the influence of the localized edge states can be independently tuned from the transmission of the ballistic channel in such devices (see Figure).