Journal: 2D Materials

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Publisher

IOP Publishing

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ISSN

2053-1583

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2017 - 201932020 - 20244
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Publications 1 - 7 of 7
  • Quantum capacitive coupling between large-angle twisted graphene layers
    Item type: Journal Article
    Mrenca-Kolasinska, Alina; Rickhaus, Peter; Zheng, Giulia; et al. (2022)
    2D Materials
    Large-angle twisted bilayer graphene (tBLG) is known to be electronically decoupled due to the spatial separation of the Dirac cones corresponding to individual graphene layers in the reciprocal space. The close spacing between the layers causes strong capacitive coupling, opening possibilities for applications in atomically thin devices. Here, we present a self-consistent quantum capacitance model for the electrostatics of decoupled graphene layers, and further generalize it to deal with decoupled tBLG at finite magnetic field and large-angle twisted double bilayer graphene at zero magnetic field. We probe the capacitive coupling through the conductance, showing good agreement between simulations and experiments for all the systems considered. We also propose a new experiment utilizing the decoupling effect to induce a huge and tunable bandgap in bilayer graphene by applying a moderately low bias. Our model can be extended to systems composed of decoupled graphene multilayers as well as non-graphene systems, opening a new realm of quantum-capacitively coupled materials.
  • Layer-selective synthesis of bilayer graphene via chemical vapor deposition
    Item type: Journal Article
    Yang, Ning; Choi, Kyoungjun; Robertson, John; et al. (2017)
    2D Materials
  • Evaluating arbitrary strain configurations and doping in graphene with Raman spectroscopy
    Item type: Journal Article
    Mueller, Niclas S.; Heeg, Sebastian; Alvarez, Miriam Peña; et al. (2018)
    2D Materials
    The properties of graphene depend sensitively on strain and doping affecting its behavior in devices and allowing an advanced tailoring of this material. A knowledge of the strain configuration, i.e. the relative magnitude of the components of the strain tensor, is particularly crucial, because it governs effects like band-gap opening, pseudo-magnetic fields, and induced superconductivity. It also enters critically in the analysis of the doping level. We propose a method for evaluating unknown strain configurations and simultaneous doping in graphene using Raman spectroscopy. In our analysis we first extract the bare peak shift of the G and 2D modes by eliminating their splitting due to shear strain. The shifts from hydrostatic strain and doping are separated by a correlation analysis of the 2D and G frequencies, where we find ∆ω2D/∆ωG = 2.21 ± 0.05 for pure hydrostatic strain. We obtain the local hydrostatic strain, shear strain and doping without any assumption on the strain configuration prior to the analysis, as we demonstrate for two model cases: Graphene under uniaxial stress and graphene suspended on nanostructures that induce strain. Raman scattering with circular corotating polarization is ideal for analyzing frequency shifts, especially for weak strain when the peak splitting by shear strain cannot be resolved.
  • A MOS capacitor model for ultra-thin 2D semiconductors: The impact of interface defects and channel resistance
    Item type: Journal Article
    Gaur, Abhinav; Agarwal, Tarun; Asselberghs, Inge; et al. (2020)
    2D Materials
  • Eliminating the channel resistance in two-dimensional systems using viscous charge flow
    Item type: Journal Article
    Huang, Wenhao; Paul, Tathagata; Perrin, Mickael L.; et al. (2024)
    2D Materials
    Driven by the pursuit of high-performance electronic devices and the exploration of quantum phenomena, research into two-dimensional (2D) systems and materials, has unveiled their exceptional properties and potential applications. While extensive efforts have centered on minimizing contact resistance, reducing the intrinsic channel resistance within the conducting material remains a formidable challenge. Research in this direction has focused on investigating superconductivity and ballistic transport. However, the practical applications of these phenomena are usually constrained by the requirement for cryogenic conditions. Charge transport in the hydrodynamic regime emerges as a versatile alternative, offering enhanced resilience to these challenges, and making it a promising avenue for effectively reducing channel resistance in 2D systems. The current perspective delves into charge hydrodynamics, exploring its mechanisms, recent advancements, enduring challenges, and its potential in reducing the channel resistance.
  • Fabry-Perot cavities and quantum dot formation at gate-defined interfaces in twisted double bilayer graphene
    Item type: Journal Article
    Rickhaus, Peter; Portolés, Elías; Zheng, Giulia; et al. (2022)
    2D Materials
    The rich and electrostatically tunable phase diagram exhibited by moire materials has made them a suitable platform for hosting single material, multi-purpose devices. To engineer such devices, understanding electronic transport and localization across electrostatically defined interfaces is of fundamental importance. Little is known, however, about how the interplay between the band structure originating from the moire lattice and electric potential gradients affects electronic confinement. Here, we electrostatically define a cavity across a twisted double bilayer graphene sample. We observe two kinds of Fabry-Perot (FP) oscillations. The first, independent of charge polarity, stems from confinement of electrons between dispersive-band/flat-band interfaces. The second arises from junctions between regions tuned into different flat bands. When tuning the out-of-plane electric field across the device, we observe Coulomb blockade resonances in transport. This is an indication of strong electronic confinement. From the gate, magnetic field and source-drain voltage dependences of the resonances, we conclude that quantum dots form at the interfaces of the FP cavity. Our results constitute a first step toward better understanding interfacial phenomena in single crystal moire devices.
  • Magnetotransport and lateral confinement in an InSe van der Waals Heterostructure
    Item type: Journal Article
    Lee, Yongjin; Pisoni, Riccardo; Overweg, Hiske C.; et al. (2018)
    2D Materials
Publications 1 - 7 of 7