Figure 3From: Layer-dependent nanoscale electrical properties of graphene studied by conductive scanning probe microscopy EFM phase images. EFM phase images of the same area of Figure 1 at bias voltages of +2 V (a) and -2 V (b). The phase shift of graphene with respect to that of SiO2 substrate vs the number of graphene layers obtained at +2 V and -2 V are plotted in (c) and (d), respectively.Back to article page