Theory-assisted detection of nano-rippling and impurities in STEM images of angle-mismatched bilayer graphene

ORAL

Abstract

Two-dimensional (2D) materials commonly contain ripples and impurity atoms that limit carrier mobilities, create pseudo-magnetic fields, and affect other electronic and magnetic properties. While scanning transmission electron microscopy (STEM) provides high-accuracy determination of the atomic positions and columns in the image plane, it is difficult to obtain precise atomic positions in the perpendicular direction. Detection of impurities with similar atomic numbers can also be difficult in Z-contrast imaging. In the case of multilayer 2D materials such as bilayer graphene, misalignment of the layers results in a moiré pattern that further compounds the problem of atomic identification. In this work, we introduce a combined approach utilizing STEM imaging and density-functional-theory calculations to recover this information from the experimentally accessible xy-coordinates in twisted bilayer graphene. We find that the strain-induced rippling obeys the continuum model of elasticity and that the moiré-pattern-induced undulations are approximately an order of magnitude smaller. Additionally, using the presented methodology, we are able to establish the presence of a substitutional nitrogen impurity.

*Supported by DOE Grant DE-FG-02-09ER46554 and NSF Grant DMR-1508433.

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Presenters

  • Andrew O'Hara

    • Physics, Vanderbilt University
    • Department of Physics and Astronomy, Vanderbilt University

Authors

  • Andrew O'Hara

    • Physics, Vanderbilt University
    • Department of Physics and Astronomy, Vanderbilt University

  • Oleg S Ovchinnikov

    • Institute for Functional Imaging of Materials, Oak Ridge National Laboratory
    • Department of Physics and Astronomy, Vanderbilt University

  • Jordan A. Hachtel

    • Department of Physics and Astronomy, Vanderbilt University
    • Oak Ridge National Laboratory

  • Stephen Jesse

    • Center for Nanophase Materials Science, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory

  • Sergei Kalinin

    • Institute for Functional Imaging of Materials, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory

  • Albina Y Borisevich

    • Center for Nanophase Materials Sciences, Oak Ridge National Lab
    • Materials Science and Technology Division, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory

  • Sokrates T Pantelides

    • Department of Physics and Astronomy, Vanderbilt University
    • Vanderbilt University
    • physics, Vanderbilt University
    • Physics, Vanderbilt University
    • Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University
    • Dept. of Physics and Astronomy, Vanderbilt University, USA