Mesoscopic Electron Transport in Nanostructured Graphene

We present experimental results on low energy electric transport studies in mesoscopic graphene quantum devices. Graphene sheets have been fabricated by means of micromechanical exfoliation. Subsequently we define mesoscopic Aharonov-Bohm (AB) rings. The electron interference in such ring shaped graphene ribbons is controlled using a perpendicular magnetic field. We will discuss magnetoresistance oscillations obtained on AB rings with ring width of $\sim $ 50 nm and ring diameters ranging from 300 nm to 3000 nm as a function of both temperature and carrier density. In addition, we present our efforts on locally controlling the carrier density in graphene sheets. The latter are patterned into ribbons of $\sim $ 100nm width and contacted in a first step with source and drain electrodes. In a second step multiple lithographically-patterned electrostatic local top gates are aligned to each device. We will discuss transport measurements as a function of local gate voltages.