Charge distribution in turbostratic few-layer graphene studied by carbon isotope labeling

Elucidating layer-resolved charge distribution in van der Waals stacked crystals is crucial for electronic applications based on 2D materials. Here, we use CVD-grown few-layer graphene (FLG) labeled by carbon isotopes as a prototype, in which Raman features of two isotope components identify distinct layers. Electrical transfer characteristics of graphene field-effect transistors (GFETs) are employed to quantitatively calibrate the correspondence of Fermi level and G-phonon frequency that shifts with the charge carrier concentration (n) variation. The isotope-assisted spectroscopy reveals previously unprobed characteristics that the n value of both top and bottom layers in FLG is close rather than following an exponential decay law. This negligible gradient likely benefits from the pi - pi interaction that favors the interlayer diffusion of charges. In addition, each extra layer reduces the degree of charge exchange at the graphene/dopant interface. These results have important implications for FLG nanoelectronics and provide a robust framework by which one can further investigate the critical properties of other 2D systems. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the charge distribution between layers in van der Waals stacked crystals using carbon isotope-labeled few-layer graphene. The electrical transfer characteristics of graphene field-effect transistors are used to calibrate the correspondence between Fermi level and G-phonon frequency. The results reveal that the charge concentration in both top and bottom layers of few-layer graphene is close and does not follow the exponential decay law. Additionally, each additional layer of graphene reduces the charge exchange at the graphene/dopant interface. These findings have important implications for electronic applications based on two-dimensional materials and provide a framework for further exploring the properties of other two-dimensional systems.