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(Color online) (a) Optical microscope image of GHP on SiO2/n-Si substrate. (b) Representative Raman spectrum measured on GHP (with a 473 nm laser). (c) I 2 D /IG intensity map of the Hall probe. (d) Selected traces of Rxx of the GHP as a function of the back gate voltage Vg at B = 0 tesla for temperature T = 4.2, 20, 60, and 130 K, from top to bottom. The Dirac point is ∼22 V, marked by the dotted line.
(Color online) (a) Magnetoresistance ΔRxx = Rxx (Vg , B) – Rxx (Vg , 0) of GHP measured at various gate voltages Vg at T = 10 K. (b) Hall resistance Rxy of GHP taken at T = 10 K, the Hall resistance drop to ∼0 Ω while Vg approaches the Dirac region. (c) Characteristic lengths responsible for weak localization as a function of Vg . (d) Hall coefficients measured at various T as a function of Vg . The shaded area marks the Dirac region, defined by the transition area of RH .
(Color online) (a) Noise power spectrum Sv of the Hall leads under different driving currents. The general temperature dependence and the magnitude of the flat band noises, , varying from 40 nV/Hz1/2 to 80 nV/Hz1/2 for T rising from 77 K to 300 K, can be described by Johnson noise. The traces of the upper branch (0.5 μA to 3 μA) are measured at 300 K, and those of the lower branch (7 μA and 4 μA) at 77 K. (b) SV of Rxx as a function of Vg . The dashed lines mark the cross-over frequency fc .
Room-temperature characteristic parameters, field sensitivity RH , optimal bias current Ibias , field resolution Bmin , cross-over frequency fc , and parasitic resistance Rs for three selected Hall probes.
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