Fig. 3
Electrostatic gating of chemically doped graphene (30 μm × 180 μm Hall bar). a Temperature dependence of longitudinal resistance for graphene in the metallic limit (red) and gated to Dirac point (blue). (Inset) Schematic representation of a chemically doped graphene device with a metallic gate (the topmost Au layer). b ρXX vs. carrier concentration shows the characteristic Dirac peak around the charge neutrality point (red dotted line serves as a guide to the eye). The Dirac point is crossed below Vg = −40 V, and the device has well-defined carrier densities within ±6 × 109 cm−2 at T = 2 K, which corresponds to a Fermi energy of ±9 meV. c Corresponding charge carrier mobilities, with values up to 70 000 cm2 V−1 s−1. Each point in b and c represents data of magnetic field scans where RXY is linear in the low magnetic field limit and the device shows fully developed quantum Hall effect at high magnetic fields (ρXX = 0 and exactly quantized RXY plateaus). The gap in data around zero carrier concentration corresponds to omitted data points where graphene is in the charge puddle regime. For comparison, in c, red circles and blue triangles correspond to Hall measurements from two different Hall probe pairs on the same device. The gate voltage was applied at cryogenic temperatures; the measured leakage current did not exceed 50 pA, with the bias current on graphene of 100 nA
