Graphene Nanoribbons for Electronic Devices

Geng, Zhansong; Hähnlein, Bernd; Granzner, Ralf; Auge, Manuel; Lebedev, Alexander A.; Davydov, V. Yu.; Kittler, M.; Pezoldt, Jörg; Schwierz, Frank

doi:10.1002/andp.201700033

Cited by 50 publications

(37 citation statements)

References 139 publications

(222 reference statements)

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“…It has been found that for the geometries a/b > 0.02 from Fig. 1a, b, the propagation constant k z (1) is close to the value provided by the parallel-plate waveguide model (8), and no additional iteration steps are required except one.…”

Section: Results Of Simulation and Discussionsupporting

confidence: 55%

“…These include interconnects, antennas, attenuators, transistors [4,5], and nonlinear devices [6]. Many techniques are used to realize these and other prospective components, such as chemical doping [7], integration of graphene with other materials [3], and graphene nanoribbon or nanodot elements [8]. Some problems of active and passive components are solved by staking the graphene nanosheets or using the quantum-mechanical interaction of graphene layers [9].…”

Section: Introductionmentioning

confidence: 99%

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Terahertz rectangular waveguides with inserted graphene films biased by light and their quasi-linear electromagnetic modeling

Kouzaev

2020

J Comput Electron

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Novel rectangular waveguides with graphene inserts biased by light are proposed herein. The graphene films short the conductor plates of waveguides and support the localized transverse-electric modes. Their electric fields are parallel to the wide walls of these waveguides, and the eigenmodes have decreased conductor loss. The designs do not involve the conductor and graphene strips with their sharp edges, and the loss associated with the current crowding effect is excluded. The waveguides are treated in the quasi-linear regime using a rigorous field matching method, and the complex dispersion eigenmodal equation is solved using a validated iteration algorithm. At the terahertz frequencies of amplification, where the real part of graphene conductivity is negative, a gain increase is found with the eigenmodal number. This gain can be tuned by the waveguide geometry, dielectric filling, and the level of quasi-Fermi energy. The ideal waveguide theory is corrected using a perturbation approach and the Drude model of surface resistance of waveguide plates.

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Section: Results Of Simulation and Discussionsupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Terahertz rectangular waveguides with inserted graphene films biased by light and their quasi-linear electromagnetic modeling

Kouzaev

2020

J Comput Electron

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“…石墨烯特殊的结构, 赋予其优异的物理化学性能, 如杨氏模量将近 1.0 TPa [4][5] , 断裂强度为 42 N/m [6] , 电子迁移率高达 2×10 5 cm 2 /(V•s) [7] , 热导率可达 5.30×10 3 W/(m•K) [8] . 因此, 石墨烯在复合材料 [9][10][11][12] 、电子器件 [13][14] 、能量存储 [15][16][17] 、传感器 [18][19][20] 及生物医药 [21][22][23][24] 等领域有着广泛的应用.…”

Section: 引言unclassified

Molecular Dynamics Simulation of the Stability Behavior of Graphene in Glycerol/Urea Solvents in Liquid-Phase Exfoliation

Liu¹,

Hong²,

Li³

2021

Acta Chimica Sinica

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Understanding of interfacial structure and stabilization mechanism of graphene sheets in green solvents during liquid-phase exfoliation is of great importance in advancing preparation, characterization and synthesis of graphene-based materials. However, it is difficult to monitor structural evolution of graphene in solvents using current available experimental techniques, and the resulting graphene stabilization mechanism has not been fully understood. In this work, molecular dynamics simulations are performed to investigate the structural evolution and stability behavior of the graphene sheets with different states in the glycerol/urea green solvents with varying concentrations. The results show that only the pristine graphene sheet at an initial interlayer spacing of 0.6 nm in the glycerol solvent restacks back and stays close to each other at a separation close to the intrinsic thickness of graphene. This is due to the fact that the glycerol molecules fail to diffuse into the graphene interlayer, and they could not afford a sufficient repulsive barrier to hinder the graphene aggregation. While in other pristine cases, a single-or double-layer solvent structure is formed and the interlayer separation is maintained at 0.65 nm or 1.12～1.18 nm, offering an efficient dispersion medium to stabilize the graphene sheets. Although the pristine multilayer graphene sheets present similar stability in different glycerol/urea solvents, the U-type graphene experiences distinct levels of stabilization in solvents in the order of pure glycerol＞glycerol/urea(2/1)＞glycerol/urea(3/1)＞glycerol/urea(1/1), signifying that the shifted and exfoliated state of the graphene sheets plays an important role in the stabilization during liquid-phase exfoliation. Moreover, in the glycerol/urea binary solvents, the small urea molecules firstly diffuse into the graphene interlayer due to their strong π-π interaction with graphene, acting as a "dispersion initiator". And then the glycerol molecules could have the chance to diffuse around or insert into the graphene interlayer to assist in stabilizing the graphene due to the hydrogen bonding between urea and glycerol. In this way, the glycerol helps to further increase the interlayer separation leading to a more stable dispersion, acting as a "dispersion co-stabilizer". The formation of the confined urea and glycerol solvents thus provides a stable molecular layer structure between the graphene interlayer, enabling to stabilize the exfoliated graphene sheets effectively. As such, the findings in this work are believed to provide the atomic/molecular scale understanding of the stability behavior of the graphene sheets in glycerol/urea binary solvents during liquid-phase exfoliation.

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“…The interfaces between such bubble and substrate (in the case of epitaxial graphene SiC) display unique capacitance effects which lead to the emergence of a mini gap in the electronic band structure of graphene of approximately ⁓5 meV. Therefore, the potential of graphene and graphene containing materials for future applications is immense and already shows promise in fields like nano-electronics [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ], nonlinear optics [ 40 ] and plasmonics [ 41 ].…”

Section: Introductionmentioning

confidence: 99%

Raman Spectroscopy Imaging of Exceptional Electronic Properties in Epitaxial Graphene Grown on SiC

et al. 2020

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Graphene distinctive electronic and optical properties have sparked intense interest throughout the scientific community bringing innovation and progress to many sectors of academia and industry. Graphene manufacturing has rapidly evolved since its discovery in 2004. The diverse growth methods of graphene have many comparative advantages in terms of size, shape, quality and cost. Specifically, epitaxial graphene is thermally grown on a silicon carbide (SiC) substrate. This type of graphene is unique due to its coexistence with the SiC underneath which makes the process of transferring graphene layers for devices manufacturing simple and robust. Raman analysis is a sensitive technique extensively used to explore nanocarbon material properties. Indeed, this method has been widely used in graphene studies in fundamental research and application fields. We review the principal Raman scattering processes in SiC substrate and demonstrate epitaxial graphene growth. We have identified the Raman bands signature of graphene for different layers number. The method could be readily adopted to characterize structural and exceptional electrical properties for various epitaxial graphene systems. Particularly, the variation of the charge carrier concentration in epitaxial graphene of different shapes and layers number have been precisely imaged. By comparing the intensity ratio of 2D line and G line—“I2D/IG”—the density of charge across the graphene layers could be monitored. The obtained results were compared to previous electrical measurements. The substrate longitudinal optical phonon coupling “LOOPC” modes have also been examined for several epitaxial graphene layers. The LOOPC of the SiC substrate shows a precise map of the density of charge in epitaxial graphene systems for different graphene layers number. Correlations between the density of charge and particular graphene layer shape such as bubbles have been determined. All experimental probes show a high degree of consistency and efficiency. Our combined studies have revealed novel capacitor effect in diverse epitaxial graphene system. The SiC substrate self-compensates the graphene layer charge without any external doping. We have observed a new density of charge at the graphene—substrate interface. The located capacitor effects at epitaxial graphene-substrate interfaces give rise to an unexpected mini gap in graphene band structure.

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Graphene Nanoribbons for Electronic Devices

Cited by 50 publications

References 139 publications

Terahertz rectangular waveguides with inserted graphene films biased by light and their quasi-linear electromagnetic modeling

Terahertz rectangular waveguides with inserted graphene films biased by light and their quasi-linear electromagnetic modeling

Molecular Dynamics Simulation of the Stability Behavior of Graphene in Glycerol/Urea Solvents in Liquid-Phase Exfoliation

Raman Spectroscopy Imaging of Exceptional Electronic Properties in Epitaxial Graphene Grown on SiC

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