Measurement of the Optical Conductivity of Graphene

Mak, Kin Fai; Sfeir, Matthew Y.; Wu, Yang; Lui, Chun Hung; Misewich, James A.; Heinz, Tony F.

doi:10.1103/physrevlett.101.196405

Cited by 1,528 publications

(1,311 citation statements)

References 30 publications

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“…Optical transmission and reflection have also been extensively used. 8,9 The optical behaviour of twisted bilayer graphene has been studied by Raman spectroscopy 10 and optical conductivity measurements. 11 Recently, graphene optical properties have found an application in photonic materials, 12 and differential transmission spectra have been used to explore the electronacoustic phonon coupling.…”

Section: Introductionmentioning

confidence: 99%

Determination of a refractive index and an extinction coefficient of standard production of CVD-graphene

et al. 2015

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The refractive index and extinction coefficient of chemical vapour deposition grown graphene are determined by ellipsometry analysis. Graphene films were grown on copper substrates and transferred as both monolayers and bilayers onto SiO 2 /Si substrates by using standard manufacturing procedures. The chemical nature and thickness of residual debris formed after the transfer process were elucidated using photoelectron spectroscopy. The real layered structure so deduced has been used instead of the nominal one as the input in the ellipsometry analysis of monolayer and bilayer graphene, transferred onto both native and thermal silicon oxide. The effect of these contamination layers on the optical properties of the stacked structure is noticeable both in the visible and the ultraviolet spectral regions, thus masking the graphene optical response. Finally, the use of heat treatment under a nitrogen atmosphere of the graphene-based stacked structures, as a method to reduce the water content of the sample, and its effect on the optical response of both graphene and the residual debris layer are presented. The Lorentz-Drude model proposed for the optical response of graphene fits fairly well the experimental ellipsometric data for all the analysed graphene-based stacked structures.

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Section: Introductionmentioning

confidence: 99%

Determination of a refractive index and an extinction coefficient of standard production of CVD-graphene

et al. 2015

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“…The black membrane consists of the PAN nanofibers and the loaded CB nanoparticles (see Figure S1, Supporting Information) with diameter of tens of nanometers, as shown in Figure 2e. The white membrane turns to be completely black after the CB deposition, which can be attributed to the sp 2 orbital hybridization and thus induced π‐π electron transition of the carbon materials 36, 37. Note that, both the white and black membranes are tightly attached to the leaf surface (i.e., cuticle).…”

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confidence: 99%

Tuning Transpiration by Interfacial Solar Absorber‐Leaf Engineering

Zhuang

Lin

et al. 2017

Advanced Science

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Plant transpiration, a process of water movement through a plant and its evaporation from aerial parts especially leaves, consumes a large component of the total continental precipitation (≈48%) and significantly influences global water distribution and climate. To date, various chemical and/or biological explorations have been made to tune the transpiration but with uncertain environmental risks. In recent years, interfacial solar steam/vapor generation is attracting a lot of attention for achieving high energy transfer efficiency. Various optical and thermal designs at the solar absorber–water interface for potential applications in water purification, seawater desalination, and power generation appear. In this work, the concept of interfacial solar vapor generation is extended to tunable plant transpiration by showing for the first time that the transpiration efficiency can also be enhanced or suppressed through engineering the solar absorber–leaf interface. By tuning the solar absorption of membrane in direct touch with green leaf, surface temperature of green leaf will change accordingly because of photothermal effect, thus the transpiration efficiency as well as temperature and relative humidity in the surrounding environment will be tuned. This tunable transpiration by interfacial absorber‐leaf engineering can open an alternative avenue to regulate local atmospheric temperature, humidity, and eventually hydrologic cycle.

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“…: reduced Planck constant) for interband transitions in a wide spectral range. [18][19][20][21] On the other hand, experimental studies of the intraband conductivity have been very limited, [21][22][23][24] Here, we describe our THz and MIR spectroscopy study of large-area (centimeter scale), single-layer graphene with an electrically tunable Fermi level. In a field-effect transistor configuration consisting of graphene on a SiO 2 /p-Si substrate, the transmitted intensity of THz and MIR electromagnetic waves was observed to change with the gate voltage.…”

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confidence: 99%

Terahertz and Infrared Spectroscopy of Gated Large-Area Graphene

Zhang²,

et al. 2012

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We have fabricated a centimeter-size single-layer graphene device, with a gate electrode, which can modulate the transmission of terahertz and infrared waves. Using time-domain terahertz spectroscopy and Fourier-transform infrared spectroscopy in a wide frequency range (10-10000 cm -1 ), we measured the dynamic conductivity change induced by electrical gating and thermal annealing.Both methods were able to effectively tune the Fermi energy, E F , which in turn modified the Drude-like intraband absorption in the terahertz as well as the '2E F onset' for interband absorption in the midinfrared. These results not only provide fundamental insight into the electromagnetic response of Dirac fermions in graphene but also demonstrate the key functionalities of large-area graphene devices that are desired for components in terahertz and infrared optoelectronics. KEYWORDS: graphene, Fermi level, terahertz dynamics, infrared spectroscopyThe AC dynamics of Dirac fermions in graphene have attracted much recent attention. The influence of linear dispersions, two-dimensionality, electron-electron interactions, and disorder on the dynamic conductivity, σ(ω), has been theoretically investigated, 1-11 whereas unique terahertz (THz) and mid-infrared (MIR) properties have been identified for novel optoelectronic applications. 12-17 For example, it has been predicted that the response of Dirac fermions to an applied AC electric field of frequency ω would automatically contain all odd harmonics of (2n+1)ω, where n is an integer, implying extremely high nonlinearity. 13,14 Furthermore, creation of electrons and holes through interband optical pumping is expected to lead to population inversion near the Dirac point, resulting in negative σ(ω), or gain, in the THz to MIR range. 12,17 While initial experimental investigations on graphene have concentrated on DC characteristics, these recent theoretical studies have instigated a flurry of new experimental activities to uncover unusual AC properties. A number of experiments have already confirmed the so-called universal optical conductivity σ 0 = e 2 /4 ! (e: electronic charge and ! : reduced Planck constant) for interband transitions in a wide spectral range. [18][19][20][21] On the other hand, experimental studies of the intraband conductivity have been very limited, [21][22][23][24] Here, we describe our THz and MIR spectroscopy study of large-area (centimeter scale), single-layer graphene with an electrically tunable Fermi level. In a field-effect transistor configuration consisting of graphene on a SiO 2 /p-Si substrate, the transmitted intensity of THz and MIR electromagnetic waves was observed to change with the gate voltage. The Drude-like intraband conductivities and the '2E F onset' of the interband transitions, monitored through time-domain THz spectroscopy (TDTS) and Fourier-transform IR (FTIR) spectroscopy, respectively, were both modulated by the gate voltage. By analyzing the spectral shape of the induced changes with appropriate models, we were able to determine ...

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Measurement of the Optical Conductivity of Graphene

Cited by 1,528 publications

References 30 publications

Determination of a refractive index and an extinction coefficient of standard production of CVD-graphene

Determination of a refractive index and an extinction coefficient of standard production of CVD-graphene

Tuning Transpiration by Interfacial Solar Absorber‐Leaf Engineering

Terahertz and Infrared Spectroscopy of Gated Large-Area Graphene

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