Electronic transport and scattering times in tungsten-decorated graphene

Jamie A. Elias and Erik A. Henriksen

Phys. Rev. B 95, 075405 – Published 7 February 2017

Abstract

The electronic transport properties of a monolayer graphene device have been studied before and after the deposition of a dilute coating of tungsten adatoms on the surface. For coverages up to 2.5% of a monolayer, we find tungsten adatoms simultaneously donate electrons to graphene and reduce the carrier mobility, impacting the zero- and finite-field transport properties. Two independent transport analyses suggest the adatoms lie nearly 1 nm above the surface. The presence of adatoms is also seen to impact the low-field magnetoresistance, altering the signatures of weak localization.

Received 30 October 2016
Revised 2 January 2017

DOI:https://doi.org/10.1103/PhysRevB.95.075405

Physics Subject Headings (PhySH)

Graphene Surfaces

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Jamie A. Elias¹ and Erik A. Henriksen^1,2,*

¹Department of Physics, Washington University in St. Louis, 1 Brookings Dr., St. Louis, Missouri 63130, USA
²Institute for Materials Science & Engineering, Washington University in St. Louis, 1 Brookings Dr., St. Louis, Missouri 63130, USA

^*henriksen@wustl.edu

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 95, Iss. 7 — 15 February 2017

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) Conductivity $σ$ vs gate voltage $V_{g}$ for the monolayer graphene Hall bar sample shown inset to the figure. The as-made sample has a conductivity minimum at $V_{g 0} = 10$ V, which shifts to the left indicating electron doping after each of three subsequent tungsten evaporations. Black dashed lines show linear fits used to extract the field-effect carrier mobility. (b) The gate voltage shift, $Δ V_{g} = V_{g, \min} - V_{g 0}$ , with $V_{g, \min}$ the gate voltage position of the minimum conductivity in part (a) for each evaporation, plotted against the change in the inverse mobility, where $μ_{0}$ is the mobility of the as-made trace [red curve in part (a)]. The shift has a power law dependence on the inverse mobility with a slope of 1.4, consistent with pointlike scattering [3, 26, 29].
Reuse & Permissions
Figure 2
(a) Representative Shubnikov-de Haas trace after the second W evaporation, at a density $n = 4.3 \times 10^{12} {cm}^{- 2}$ . (b) The corresponding analysis of the temperature-corrected oscillation amplitudes vs $B^{- 1}$ after Coleridge [35] and Hong [36]; the linear fit is constrained to a $y$ intercept of 4, and the slope is proportional to the quantum scattering rate $τ_{q}^{- 1}$ . (c),(d) Transport and quantum scattering times extracted from conductivity data of Fig. 1 and analysis of SdH traces, respectively. Red dashed lines are $\sqrt{n}$ fits to red circles. (e) Ratio of transport to quantum scattering time, $τ_{μ} / τ_{q}$ , vs carrier density $n$ for the as-made sample and after each evaporation. Uncertainty in the data is given by the symbol size. The dashed black lines are calculated using the theory of Hwang and Das Sarma [37], for the case of pure charged impurity scattering.
Reuse & Permissions
Figure 3
Low-field magnetoresistance for a carrier density $n = 1.4 \times 10^{12} {cm}^{- 2}$ , showing characteristic WL peaks about $B = 0$ . Traces are vertically offset for clarity. The dashed black lines are fits using Eq. (2), with the field range restricted to the diffusive regime ${(l_{μ} / l_{B})}^{2} ≪ 1$ ; the fitting parameters are plotted in Fig. 4.
Reuse & Permissions
Figure 4
Phase-breaking time $τ_{ϕ}$ and intervalley scattering time $τ_{i}$ extracted from curve fits to the low-field magnetoresistance using Eq. (2), as illustrated in Fig. 3. The theoretical phase breaking times calculated with Eq. (3) are shown as lines in the upper portion of the figure, using data from the as-made sample (dashed red) and after the 3rd evaporation (dotted blue). Trends in the data reflect the increase (decrease) in conductivity with carrier density (successive evaporations).
Reuse & Permissions

Physical Review B

covering condensed matter and materials physics