Abstract:The transport properties of electronic materials have been long interpreted independently from both the underlying bulk-like behavior of the substrate or the influence of ambient gases. This is no longer the case for ultra-thin graphene whose properties are dominated by the interfaces between the active material and its surroundings. Here, we show that the graphene interactions with its environments are critical for the electrostatic and electrochemical equilibrium of the active device layers and their transpo… Show more
“…This behavior is consistent with previous results on epitaxial graphene on SiC 6, 16 . The change in N
s from air exposure can be explained by a redox reaction at the surface of the graphene involving various environmental gases, which results in electron withdrawal 5 . Exposure to an inert gas, such as nitrogen or helium, is thought to cause the doping agents at the graphene surface to desorb, which reverses the electron withdrawal.Figure 2Best-match model results for sheet carrier density N
s and mobility μ as a function of time.…”
Section: Resultsmentioning
confidence: 99%
“…2 is an ambient acceptor doping redox reaction at the graphene surface involving O 2 , H 2 O, and CO 2
5 . To summarize this previously proposed mechanism, first thin films of water form at surfaces when exposed to ambient.…”
Unraveling the doping-related charge carrier scattering mechanisms in two-dimensional materials such as graphene is vital for limiting parasitic electrical conductivity losses in future electronic applications. While electric field doping is well understood, assessment of mobility and density as a function of chemical doping remained a challenge thus far. In this work, we investigate the effects of cyclically exposing epitaxial graphene to controlled inert gases and ambient humidity conditions, while measuring the Lorentz force-induced birefringence in graphene at Terahertz frequencies in magnetic fields. This technique, previously identified as the optical analogue of the electrical Hall effect, permits here measurement of charge carrier type, density, and mobility in epitaxial graphene on silicon-face silicon carbide. We observe a distinct, nearly linear relationship between mobility and electron charge density, similar to field-effect induced changes measured in electrical Hall bar devices previously. The observed doping process is completely reversible and independent of the type of inert gas exposure.
“…This behavior is consistent with previous results on epitaxial graphene on SiC 6, 16 . The change in N
s from air exposure can be explained by a redox reaction at the surface of the graphene involving various environmental gases, which results in electron withdrawal 5 . Exposure to an inert gas, such as nitrogen or helium, is thought to cause the doping agents at the graphene surface to desorb, which reverses the electron withdrawal.Figure 2Best-match model results for sheet carrier density N
s and mobility μ as a function of time.…”
Section: Resultsmentioning
confidence: 99%
“…2 is an ambient acceptor doping redox reaction at the graphene surface involving O 2 , H 2 O, and CO 2
5 . To summarize this previously proposed mechanism, first thin films of water form at surfaces when exposed to ambient.…”
Unraveling the doping-related charge carrier scattering mechanisms in two-dimensional materials such as graphene is vital for limiting parasitic electrical conductivity losses in future electronic applications. While electric field doping is well understood, assessment of mobility and density as a function of chemical doping remained a challenge thus far. In this work, we investigate the effects of cyclically exposing epitaxial graphene to controlled inert gases and ambient humidity conditions, while measuring the Lorentz force-induced birefringence in graphene at Terahertz frequencies in magnetic fields. This technique, previously identified as the optical analogue of the electrical Hall effect, permits here measurement of charge carrier type, density, and mobility in epitaxial graphene on silicon-face silicon carbide. We observe a distinct, nearly linear relationship between mobility and electron charge density, similar to field-effect induced changes measured in electrical Hall bar devices previously. The observed doping process is completely reversible and independent of the type of inert gas exposure.
“…35,[42][43][44][45][46][47][48] Furthermore, humidity enhances hole doping by O 2 . 49 Sque et al specifically suggested that graphene could undergo transfer doping to the aqueous oxygen redox couple.…”
Vacuum-annealed semiconducting single walled nanotubes are n-type, but become p-type when exposed to ambient air. Here we present evidence that this effect arises from pinning of the Fermi energy by the four-electron oxygen redox couple in an adsorbed water film, a type of surface transfer doping. The pronounced electrical sensitivity to O 2 , O 3 , NO 2 , SO 2 , NH 3 and HNO 3 vapors results from electron exchange between the redox couple and the nanotube. This effect must be considered when using nanotubes for any application in humid air. We also suggest that changes in the electrical properties of graphene and multi-walled nanotubes can be explained by this phenomenon.
“…A similar absolute value of Seebeck coefficient was found for single layer graphene made by chemical vapor deposition on Cu (6 lV/ C) 28 or for multilayer epitaxial graphene on Si (À30 lV/ C). 29 It should be stressed here that the Seebeck coefficient can show different values (from 6 lV/ C to 180 lV/ C) and depends highly on the method of sample preparation, measurements method, sample thickness, etc. 30 …”
We report fabrication of reduced graphene oxide (rGO) films using chemical reduction by hydrazine hydrate and rGO paper-like samples using low temperature treatment reduction. Structural analysis confirms the formation of the rGO structure for both samples. Current-voltage (I V) measurements of the rGO film reveal semiconductor behavior with the maximum current value of $3 Â 10 4 A. The current for the rGO paper sample is found to be, at least, one order of magnitude higher. Moreover, bipolar resistance switching, corresponding to memristive behavior of type II, is observed in the I V data of the rGO paper. Although precise values of the rGO film conductivity and the Seebeck coefficient could not be measured, rGO paper shows an electrical conductivity of 6.7 Â 10 2 S/m and Seebeck coefficient of À6 lV/ C. Thus, we demonstrate a simplified way for the fabrication of rGO paper that possesses better and easier measurable macroscopic electrical properties than that of rGO thin film. Published by AIP Publishing. [http://dx
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