Transport in indium-decorated graphene

U. Chandni, Erik A. Henriksen, and J. P. Eisenstein

Phys. Rev. B 91, 245402 – Published 1 June 2015

Abstract

The electronic-transport properties of single-layer graphene that has a dilute coating of indium adatoms have been investigated. Our studies establish that isolated indium atoms donate electrons to graphene and become a source of charged impurity scattering, affecting the conductivity as well as magnetotransport properties of the pristine graphene. Notably, a positive magnetoresistance is observed over a wide density range after In doping. The low-field magnetoresistance carries signatures of quantum interference effects which are significantly altered by the adatoms.

Received 13 March 2015
Revised 11 May 2015

DOI:https://doi.org/10.1103/PhysRevB.91.245402

Authors & Affiliations

U. Chandni, Erik A. Henriksen^*, and J. P. Eisenstein

Institute of Quantum Information and Matter, Department of Physics, California Institute of Technology, 1200 E. California Boulevard, Pasadena, California 91125, USA

^*Present address: Department of Physics, Washington University in St. Louis, St. Louis, Missouri 63130, USA; henriksen@wustl.edu

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Vol. 91, Iss. 24 — 15 June 2015

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Images

Figure 1
(a) Contrast-enhanced image of single-layer graphene Hall bar device. The Hall bar has both a wide (8 $μ m$ ) region and a narrow (1 $μ m$ ) region. (b) Resistivity $ρ_{x x}$ vs density $n$ at $T = 12$ K for the wide (red) and narrow (blue) regions of the graphene device prior to deposition with In adatoms. (c) Plot of the conductivity $σ_{x x}$ vs $n$ clearly reveals a weak sublinear contribution to the density dependence of $σ_{x x}$ in the as-made device.
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Figure 2
Effect of In deposition on graphene conductivity $σ_{x x}$ vs gate voltage $V_{g}$ at $T = 12$ K. Data is from the wide region of the Hall bar, with trace (a) taken before any In deposition, trace (b) after the first In deposition, trace (c) after warming the sample to 450 K, and finally trace (d) after a second In deposition.
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Figure 3
Hall coefficient vs density near the Dirac point. The red and blue data points correspond to $R_{H}$ measurements before and after the deposition of about $2.5 \times 10^{12} {cm}^{- 2}$ indium adatoms, respectively. The dashed curve shows the ideal $R_{H} = - 1 / n e$ behavior, while the two solid lines display convolutions of the ideal behavior with Gaussian density distributions of rms width $σ_{n} = 0.3$ and $0.6 \times 10^{12} {cm}^{- 2}$ .
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Figure 4
Effect of In adatoms on the magnetoresistance of graphene. (a) $Δ ρ_{x x} / ρ_{x x}$ vs $B$ at $n = - 2.8 \times 10^{12} {cm}^{- 2}$ . The red trace corresponds to clean graphene sample, while for the blue trace, approximately $2.5 \times 10^{12} {cm}^{- 2}$ In adatoms are present. (b),(c) Magnetoresistance at various free carrier densities in the clean and In-decorated sample, respectively. Red, green, blue, magenta, and black traces: $n = 0$ , 0.7, 1.4, 2.8, and $5.6 \times 10^{12} {cm}^{- 2}$ . All data at $T = 12$ K.
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Figure 5
Low-field magnetoconductance observed in the narrow region of the sample at a free carrier density of $n = 5.5 \times 10^{12} {cm}^{- 2}$ . (a) Clean sample at $T = 12$ , 20, 33, and 50 K. (b) Effect of In deposition on $Δ σ$ at $T = 12$ K. Blue: clean sample. Green (red): After deposition of approximately 2.5 (4.5) $\times 10^{12} {cm}^{- 2}$ In adatoms. (c) Magnetoconductance at $T = 12$ , 20, 33, and 50 K of sample decorated with $2.5 \times 10^{12} {cm}^{- 2}$ In adatoms.
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Figure 6
Results of weak-localization data analysis at $n \approx 5 \times 10^{12} {cm}^{- 2}$ . (a) Examples of fits (dashed lines) of Eq. (2) to data (solid lines) at $T = 12$ K. Blue: clean graphene sample; Red: after deposition of approximately $2.5 \times 10^{12} {cm}^{- 2}$ indium adatoms. (b) Fitted values of $τ_{ϕ}$ (solid circles) and $τ_{i}$ (open circles) for the clean (blue) and In-decorated (red) graphene sample. Diagonal (horizontal) dashed lines: theory estimates of $τ_{ϕ}$ ( $τ_{μ}$ ) in graphene at mobilities 5400 (blue) and 2300 (red) ${cm}^{2}$ /Vs.
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