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Preparation of Graphene-Supported Microwell Liquid Cells for In Situ Transmission Electron Microscopy
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Moiré structures in twisted bilayer graphene studied by transmission electron microscopy
Tatiana Latychevskaia1, Conrad Escher1, Hans-Werner Fink1
1Institute of Physics, University of Zurich, Winterthurerstrasse 190, Zurich, 8057, Switzerland.
Ultramicroscopy
|November 30, 2018
Summary
Imaging twisted bilayer graphene (TBG) moiré structures requires low-energy electrons for observable diffraction peaks. This technique enhances graphene
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Twisted bilayer graphene (TBG) exhibits moiré structures crucial for its electronic properties.
- Conventional transmission electron microscopy (TEM) at high energies (80-300 keV) does not reveal moiré periodicity in diffraction patterns.
- Understanding moiré structure imaging is key for advanced graphene applications.
Purpose of the Study:
- To investigate moiré structure imaging in free-standing TBG using TEM.
- To determine the optimal electron energy for observing moiré diffraction patterns.
- To explore the utility of Gabor holography for analyzing atomic arrangements in TBG.
Main Methods:
- Transmission electron microscopy (TEM) in diffraction mode.
- In-line Gabor holography.
- Utilizing low-energy electron diffraction (LEED) in the range of tens of eV.
- Acquiring diffraction patterns at 236 eV.
Main Results:
- High-energy electron diffraction (80-300 keV) shows peaks from individual graphene layers but not moiré patterns.
- Low-energy electrons (e.g., 236 eV) reveal distinct diffraction peaks corresponding to the moiré structure periodicity.
- Gabor holography demonstrates intensity variations in the far-field related to atomic stacking (AA/AB), not necessarily absorption.
Conclusions:
- Low-energy electron diffraction is essential for imaging moiré structures in TBG.
- Intensity changes in Gabor holography are linked to atomic arrangement, offering insights beyond absorption.
- These findings are significant for utilizing graphene as a support in electron imaging techniques.
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