Atomic-Resolution Visualization and Doping Effects of Complex Structures in Intercalated Bilayer Graphene

Abstract

Molecules intercalating two-dimensional (2D) materials form complex structures that have been mostly characterized by spatially averaged techniques. Here we use aberration-corrected scanning transmission electron microscopy and density-functional-theory (DFT) calculations to study the atomic structure of bilayer graphene (BLG) and few-layer graphene (FLG) intercalated with FeCl${}_3$. In BLG we discover two distinct intercalated structures that we identify as monolayer-FeCl${}_3$ and monolayer-FeCl${}_2$. The two structures are separated by atomically sharp boundaries and induce large but different free-carrier densities in the graphene layers, $7.1\times 10^{13}$ cm${}^{-2}$ and $7.1\times 10^{13}$ cm${}^{-2}$ respectively. In FLG, we observe multiple FeCl${}_3$ layers stacked in a variety of possible configurations with respect to one another. Finally, we find that the microscope's electron beam can convert the FeCl${}_3$ monolayer into FeOCl monolayers in a rectangular lattice. These results reveal the need for a combination of atomically-resolved microscopy, spectroscopy, and DFT calculations to identify intercalated structures and study their properties.

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Cited by in corpus (3)

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• Bilayer graphene as a template for manufacturing novel 2D materials
• Formation energies of charged defects in two-dimensional materials -- resolution of long-standing difficulties