Camara et al. Nanoscale Research Letters 2011, 6:141 http://www.nanoscalereslett.com/content/6/1/141 Page 5 of 6 Figure 5 Magnetoresistance measurements of the best sample at different temperatures. (a) Longitudinal and transverse resistances of low p-type doped (ns = 8 × 1011 cm-2) epitaxial monolayer versus applied magnetic field B, at different temperatures. (b) Temperature dependence of the resistivity rxx of a graphene ribbon at different magnetic field values close to the filling factor v = 3. The slope in the semilog scale gives the activation energy Ea, which is the energy difference between the Fermi energy and the mobility edge of the second (N = 1) Landau level. [22]. However, the extracted density is systematically larger than r0 over the whole investigated energy range. This observation, combined with the fact that hopping was neglected, indicates that more detailed investiga- tions are still needed. Finally, since EG has recently been proposed for metrological application, we plot, in Figure 7, the longi- tudinal resistance as a function of the current at B = 13.5 T. This magnetic field is far from the filling factor υ = 2 and; therefore, the breakdown occurs at relatively low current: I = 0.5 μA, which corresponds to a current density j = 0.025 A/m. By comparison, for III-V hetero- structures, critical current values of 1 A/m are reported. Conclusion To summarize, we have shown the possibility to grow large islands of monolayer graphene on the C-face of on-axis and 8° off-axis commercial 4H-SiC wafers. The graphene layers are continuous, almost free-standing and show quantum transport properties comparable with high-qual- ity, low-doped, exfoliated graphene. We show evidence of half-integer QHE specific of graphene monolayer and give a first estimate of the density of states in the magnetic field. Figure 7 Longitudinal resistance (in ohms) as a function of the injected current. Breakdown of the quantization occurs at I = 0.5 μA. Figure 6 Density of states r(E) as a function of the energy Ea. For comparison, the density of states without magnetic field at EF = 100 meV is indicated by an arrow.