Quantum Hall Effect in Hydrogenated Graphene

J. Guillemette, S. S. Sabri, Binxin Wu, K. Bennaceur, P. E. Gaskell, M. Savard, P. L. Lévesque, F. Mahvash, A. Guermoune, M. Siaj, R. Martel, T. Szkopek, and G. Gervais

Phys. Rev. Lett. 110, 176801 – Published 22 April 2013

Abstract

The quantum Hall effect is observed in a two-dimensional electron gas formed in millimeter-scale hydrogenated graphene, with a mobility less than $10 {cm}^{2} / V \cdot s$ and corresponding Ioffe-Regel disorder parameter $(k_{F} λ)^{- 1} ≫ 1$ . In a zero magnetic field and low temperatures, the hydrogenated graphene is insulating with a two-point resistance of the order of $250 h / e^{2}$ . The application of a strong magnetic field generates a negative colossal magnetoresistance, with the two-point resistance saturating within 0.5% of $h / 2 e^{2}$ at 45 T. Our observations are consistent with the opening of an impurity-induced gap in the density of states of graphene. The interplay between electron localization by defect scattering and magnetic confinement in two-dimensional atomic crystals is discussed.

Received 7 January 2013

DOI:https://doi.org/10.1103/PhysRevLett.110.176801

Authors & Affiliations

J. Guillemette^1,2, S. S. Sabri², Binxin Wu¹, K. Bennaceur¹, P. E. Gaskell², M. Savard¹, P. L. Lévesque³, F. Mahvash^2,4, A. Guermoune^2,4, M. Siaj⁴, R. Martel³, T. Szkopek², and G. Gervais^1,*

¹Department of Physics, McGill University, Montréal, Quebec, H3A 2T8, Canada
²Department of Electrical and Computer Engineering, McGill University, Montréal, Quebec, H3A 2A7, Canada
³Department of Chemistry, Université de Montréal, Montréal, Quebec, H3C 3J7, Canada
⁴Department of Chemistry, Université du Québec à Montréal, Montréal, Quebec, H3C 3P8, Canada

^*Corresponding author. gervais@physics.mcgill.ca

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Vol. 110, Iss. 17 — 26 April 2013

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Images

Figure 1
Schematic of graphene hydrogenation. (a) An electrically contacted CVD grown graphene sample is exposed to reactive hydrogen atoms produced by thermal cracking of hydrogen at $T > 1800 K$ in a UHV environment. (b) The two-point resistance $R_{2 pt}$ of the graphene sheet is measured in situ with hydrogen dosing. A photograph of the device is shown. (c) The typical evolution of room temperature resistance versus hydrogen exposure time (circles), and an exponential fit to resistance versus hydrogen dose (dotted line).Reuse & Permissions
Figure 2
Characterization of the hydrogenated graphene devices. (a) Raman Stokes spectrum of CVD graphene (lower trace) and hydrogenated CVD graphene (higher trace). Peaks associated with $s p^{2}$ carbon are classified $G$ , and peaks associated with disorder are classified $D$ , respectively. The ratio $I_{D} / I_{G}$ of $D$ peak intensity to $G$ peak intensity is 2.2 and 0.15 for hydrogenated CVD graphene and pristine CVD graphene, respectively, with the corresponding mean defect spacing $λ_{D}$ estimated to be $4.6 \pm 0.5 nm$ and $\sim 35 nm$ (see text). (b) The temperature dependence of the resistance is insulating ( $d R_{2 pt} / d T < 0$ ) at all gate voltages. The field effect (inset) shows hole conduction and a zero field effect mobility regime at low hole density.Reuse & Permissions
Figure 3
Quantum Hall effect in hydrogenated graphene. (a) The two-point resistance of the hydrogenated graphene sheet is shown versus the magnetic field and the gate voltage. The resistance axis is shown on a logarithmic scale, in units of the resistance quantum $R_{q} = h / e^{2}$ . All data were taken at a temperature of $575 \pm 25 mK$ . (b) At 45 T, the resistance versus gate voltage (upper $x$ axis) and hole density (lower $x$ axis), with the red line indicating a Hall plateau at $R = h / 2 e^{2}$ . The inset shows the resistance at 21 V gate voltage approach the quantum Hall state plateau with increasing magnetic field. (c) Resistance of the hydrogenated graphene at 21 V gate voltage plotted versus both the magnetic field (lower $x$ axis) and magnetic length $l_{B}$ (upper $x$ axis). The shaded region indicates the estimated point defect spacing extracted from the Raman spectra.Reuse & Permissions
Figure 4
Ioffe-Regel–Wigner-Seitz diagram for the main families of materials exhibiting the quantum Hall effect. The figure shows the zero-field value of the Ioffe-Regel disorder parameter $(k_{F} λ)^{- 1}$ plotted versus the Wigner-Seitz radius $r_{s}$ , both dimensionless, for the main 2DEG families in which the integer and fractional quantum Hall effect was observed. A brief description of the material system, indexed numerically, is given in the upper right. The size of the labeled regions is representative of the parameter range from observed mobilities and densities. The dashed line shows the Ioffe-Regel limit where $k_{F} λ = 1$ . The Wigner crystal (WC), thought to occur at large $r_{s}$ and low disorder, is highlighted in green.Reuse & Permissions

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