Quantum transport in graphene

After the experimental discovery of graphene -a single atomic layer of graphite- a scientific rush started to explore graphene’s electronic behaviour. Graphene is a fascinating two-dimensional electronic system, because its electrons behave as relativistic particles. Moreover, it is a promising material for future high-speed nano-electronic applications. In this thesis, several experiments are described to reveal graphene’s electronic transport properties. We have shown that we can control the bandstructure of bilayer and trilayer graphene. Simply by applying a perpendicular electric field in a graphene device, we could tune the bandgap in the bilayer and the bandoverlap in the trilayer. Furthermore, we have described transport measurements on graphene devices (length = 0.1-1 micrometer) showing that electronic transport in graphene is phase coherent at cryogenic temperatures (4 K or less). We have observed weak localization, bipolar supercurrents and the Aharonov-Bohm effect. We have also shown that in narrow graphene nanoribbons (width less than 100 nm) a transport gap appears, which can be well explained by strong localization of electronic states. Our experimental results provide a better understanding of electronic transport in graphene, and are also a first step towards the realization of graphene nano-electronic devices.Kavli Institute of Nanoscience DelftApplied Science