Sub-micrometer four-point probe transport measurements on graphene

Usually, electronic transport measurements on two-dimensional materials, such as graphene and transition metal dichalcogenides, require deposition of electrodes on top of the material, in, for instance, the form of a Hall bar device. In this work, we show that by making use of a collinear micro-four-point probe, electrical transport measurements on small flakes of graphene can be performed without having to fabricate electrodes on top of the flakes. Using probes with probe pitches down to sub-micrometer scale, we show back-gate tuned transport measurements in graphene on silicon oxide and on hexagonal boron nitride. The charge carrier mobilities and the minimum conductivity of graphene are in good agreement with conventional transport measurements. In addition, we assess the possible damage caused by landing these probes on graphene.