How Perfect Can Graphene Be?

Neugebauer, Petr; Орлита, М.; Faugeras, C.; Barra, Anne‐Laure; Potemski, M.

doi:10.1103/physrevlett.103.136403

Cited by 218 publications

(114 citation statements)

References 37 publications

(45 reference statements)

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“…This extrinsic scattering mechanism is consistent with the fact that the LL lineshape is Gaussian and the linewidth is independent of energy. In contrast, for the case of graphene on graphite (25)(26)(27)(28) where scattering is intrinsic, the lineshape is Lorenztian and the linewidth, which increases linearly with energy, is almost an order of magnitude narrower than here.…”

Section: Significancecontrasting

confidence: 64%

“…Substrate interference can be eliminated by suspending the sample, an approach that led to the observation of ballistic transport (15,16) and the fractional quantum Hall effect in graphene (17)(18)(19)(20), but this method only works for small (micrometer-sized) samples at relatively low doping. Another approach is to use atomically smooth metallic substrates (21)(22)(23) or graphite (24)(25)(26)(27)(28), which screen the random potential. However, these substrates short-circuit the 2D channel and prevent tuning the carrier density by gating, rendering them unsuitable for device applications.…”

mentioning

confidence: 99%

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Local, global, and nonlinear screening in twisted double-layer graphene

Rodriguez-Vega

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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One-atom-thick crystalline layers and their vertical heterostructures carry the promise of designer electronic materials that are unattainable by standard growth techniques. To realize their potential it is necessary to isolate them from environmental disturbances, in particular those introduced by the substrate. However, finding and characterizing suitable substrates, and minimizing the random potential fluctuations they introduce, has been a persistent challenge in this emerging field. Here we show that Landau-level (LL) spectroscopy offers the unique capability to quantify both the reduction of the quasiparticles' lifetime and the long-range inhomogeneity due to random potential fluctuations. Harnessing this technique together with direct scanning tunneling microscopy and numerical simulations we demonstrate that the insertion of a graphene buffer layer with a large twist angle is a very effective method to shield a 2D system from substrate interference that has the additional desirable property of preserving the electronic structure of the system under study. We further show that owing to its remarkable nonlinear screening capability a single graphene buffer layer provides better shielding than either increasing the distance to the substrate or doubling the carrier density and reduces the amplitude of the potential fluctuations in graphene to values even lower than the ones in AB-stacked bilayer graphene.he recent realization of one-atom-thick layers and the fabrication of layered Van der Waals heterostructures revealed fascinating physical phenomena and novel devices based on interlayer interactions (1-10). Inherent to the 2D structure of these layers is an extreme vulnerability to disturbances introduced by the substrate (11)(12)(13)(14). Substrate interference can be eliminated by suspending the sample, an approach that led to the observation of ballistic transport (15, 16) and the fractional quantum Hall effect in graphene (17)(18)(19)(20), but this method only works for small (micrometer-sized) samples at relatively low doping. Another approach is to use atomically smooth metallic substrates (21-23) or graphite (24-28), which screen the random potential. However, these substrates short-circuit the 2D channel and prevent tuning the carrier density by gating, rendering them unsuitable for device applications. Among insulating substrates atomically flat hBN (29-31) and MoS 2 (6) have recently emerged as promising alternatives to SiO 2 substrates.Here we show that by inserting a graphene buffer layer between the 2D sample (in this case, also graphene) and the insulating substrate, the random potential fluctuations are screened without compromising the electronic structure of the 2D system under study and the gating capability. This capability relies on the fact that in van der Waals structures the stacking configuration in the third direction can be set arbitrarily and is not fixed by the chemistry of the elements forming the heterostructure. Consequently it is possible to electronically decouple two 2D cry...

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Section: Significancecontrasting

confidence: 64%

mentioning

confidence: 99%

Local, global, and nonlinear screening in twisted double-layer graphene

Rodriguez-Vega

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…DC relaxation time is directly proportional to the charge carrier mobility, µ , and the square root of the carrier concentration, c n . Experimental investigation of high-purity graphene, found in nature on the surface of bulk graphite, sets the low temperature scattering time limit at ps 20 ≈ τ [35]. High mobility of charge carriers has also been obtained in case of the suspended graphene [37,38], up to = µ 200 000 cm 2 /(Vs) at low temperatures and = µ 120 000 cm 2 /(Vs) near room temperature.…”

Section: Full-wave Electromagnetic Analysismentioning

confidence: 88%

“…As mentioned above, the surface conductivity of graphene at room temperature, for a given frequency , which can differ significantly in the cases of intrinsic and doped graphene [35]. Carrier relaxation time at subterahertz frequencies can be identified with the DC relaxation time,…”

Section: Full-wave Electromagnetic Analysismentioning

confidence: 99%

Graphene-based waveguide resonators for submillimeter-wave applications

Ilić

Bukvic

Ilić

et al. 2016

J. Phys. D: Appl. Phys.

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Abstract. Utilization of graphene covered waveguide inserts to form tunable waveguide resonators is theoretically explained and rigorously investigated by means of full-wave numerical electromagnetic simulations. Instead of using graphene based switching elements, the concept we propose incorporates graphene sheets as parts of a resonator. Electrostatic tuning of the graphene surface conductivity leads to changes in the electromagnetic field boundary conditions at the resonator edges and surfaces, thus producing an effect similar to varying electrical length of a resonator. Presented outline of the theoretical background serves to give phenomenological insight into the resonator behavior, but it can also be used to develop customized software tools for design and optimization of graphene based resonators and filters. Due to the linear dependence of the imaginary part of the graphene surface impedance on frequency, the proposed concept was expected to become effective for frequencies above 100 GHz, which is confirmed by the numerical simulations. Frequency range from 100 GHz up to 1100 GHz, where the rectangular waveguides are used, is considered. Simple, all-graphene based resonators are analyzed first, to assess the achievable tunability and to check the performance throughout the considered frequency range. Graphene-metal combined waveguide resonators are proposed in order to preserve excellent quality factors typical for the type of waveguide discontinuities used. Dependence of resonator properties on key design parameters is studied in detail. Dependence of resonator properties throughout the frequency range of interest is studied using eight different waveguide sections appropriate for different frequency intervals. Proposed resonators are aimed at applications in the submillimeter-wave spectral region, serving as the compact tunable components for the design of bandpass filters and other devices.

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“…Graphene/n-Si cells Figure 1(a), (b) display the morphology (SEM top and side views) of a typical graphene/ n-Si PV device. Overlapped and interconnected multiple layers of graphene sheets are observed on the n-Si substrate, which ensures a conducting pathway and provides a higher carrier mobility [24]. The graphene flakes have a 2D structure with an unexpectedly high transparency for an atomic monolayer [25].…”

Section: Methodsmentioning

confidence: 96%

Solar cells with graphene and carbon nanotubes on silicon

Zheng

Saini

et al. 2011

Journal of Experimental Nanoscience

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Graphene and carbon nanotubes (CNTs) represent attractive materials for photovoltaic (PV) devices due to their unique electronic and optical properties. Graphene and single-wall carbon nanotubes (SWNTs) layers can be directly configured as energy conversion materials to fabricate thin-film solar cells, serving as both photogeneration sites and charge carrier collecting/transport layers. SWNTs can be modified into either p-type conductor through chemical doping (like acidic purification) or n-type conductor through polymer functionalisation. The solar cells can be simply made of a semitransparent thin film of graphene (or SWNTs) deposited on a proper type of silicon substrate to create high-density Schottky (or p-n) junctions at the interface. The high aspect ratios and large surface area of these carbon nano-structured materials can benefit exciton dissociation and charge carrier transport thus improving the power conversion efficiency.

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How Perfect Can Graphene Be?

Cited by 218 publications

References 37 publications

Local, global, and nonlinear screening in twisted double-layer graphene

Local, global, and nonlinear screening in twisted double-layer graphene

Graphene-based waveguide resonators for submillimeter-wave applications

Solar cells with graphene and carbon nanotubes on silicon

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