Coulomb blockade and hopping conduction in graphene quantum dots array

We show that the low-temperature electron transport properties of chemically functionalized graphene can be explained as sequential tunneling of charges through a two-dimensional array of graphene quantum dots (GQDs). Below 15 K, a total suppression of current due to Coulomb blockade through a GQD array was observed. Temperature-dependent current-gate voltage characteristics show Coulomb oscillations with energy scales of 6.2--10 meV corresponding to GQD sizes of 5--8 nm, while resistance data exhibit an Efros-Shklovskii variable range hopping arising from structural- and size-induced disorder.