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End date: 2024 × Start date: 2020 × DDC: 540 × Publisher: Amsterdam [u.a.] : Elsevier Science × Subject: Graphene × WGL Institute: IPF ×

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    Resolving mobility anisotropy in quasi-free-standing epitaxial graphene by terahertz optical Hall effect
    (Amsterdam [u.a.] : Elsevier Science, 2021) Armakavicius, Nerijus; Kühne, Philipp; Eriksson, Jens; Bouhafs, Chamseddine; Stanishev, Vallery; Ivanov, Ivan G.; Yakimova, Rositsa; Zakharov, Alexei A.; Al-Temimy, Ameer; Coletti, Camilla; Schubert, Mathias; Darakchieva, Vanya
    In this work, we demonstrate the application of terahertz-optical Hall effect (THz-OHE) to determine directionally dependent free charge carrier properties of ambient-doped monolayer and quasi-free-standing-bilayer epitaxial graphene on 4H–SiC(0001). Directionally independent free hole mobility parameters are found for the monolayer graphene. In contrast, anisotropic hole mobility parameters with a lower mobility in direction perpendicular to the SiC surface steps and higher along the steps in quasi-free-standing-bilayer graphene are determined for the first time. A combination of THz-OHE, nanoscale microscopy and optical spectroscopy techniques are used to investigate the origin of the anisotropy. Different defect densities and different number of graphene layers on the step edges and terraces are ruled out as possible causes. Scattering mechanisms related to doping variations at the step edges and terraces as a result of different interaction with the substrate and environment are discussed and also excluded. It is suggested that the step edges introduce intrinsic scattering in quasi-free-standing-bilayer graphene, that is manifested as a result of the higher ratio between mean free path and average terrace width parameters. The suggested scenario allows to reconcile existing differences in the literature regarding the anisotropic electrical transport in epitaxial graphene. © 2020 Elsevier Ltd
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    A review of electrical and thermal conductivities of epoxy resin systems reinforced with carbon nanotubes and graphene-based nanoparticles
    (Amsterdam [u.a.] : Elsevier Science, 2022) Mousavi, Seyed Rasoul; Estaji, Sara; Kiaei, Hediyeh; Mansourian-Tabaei, Mohammad; Nouranian, Sasan; Jafari, Seyed Hassan; Ruckdäschel, Holger; Arjmand, Mohammad; Khonakdar, Hossein Ali
    Epoxy (EP) resins exhibit desirable mechanical and thermal properties, low shrinkage during cuing, and high chemical resistance. Therefore, they are useful for various applications, such as coatings, adhesives, paints, etc. On the other hand, carbon nanotubes (CNT), graphene (Gr), and their derivatives have become reinforcements of choice for EP-based nanocomposites because of their extraordinary mechanical, thermal, and electrical properties. Herein, we provide an overview of the last decade's advances in research on improving the thermal and electrical conductivities of EP resin systems modified with CNT, Gr, their derivatives, and hybrids. We further report on the surface modification of these reinforcements as a means to improve the nanofiller dispersion in the EP resins, thereby enhancing the thermal and electrical conductivities of the resulting nanocomposites.