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

TL;DR

This study uses advanced microscopy and computational methods to reveal atomic structures and doping effects in intercalated bilayer and few-layer graphene with FeCl3, discovering new intercalated phases and beam-induced transformations.

Contribution

It provides the first atomic-resolution visualization of intercalated FeCl3 structures in graphene and demonstrates how intercalation alters electronic properties and can be manipulated by electron beam.

Findings

Identified two distinct intercalated structures: monolayer-FeCl3 and monolayer-FeCl2.

Observed multiple stacking configurations of FeCl3 layers in few-layer graphene.

Electron beam can convert FeCl3 monolayers into FeOCl monolayers.

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, $7.1\times10^{13}$ cm$^{-2}$ and $7.1\times10^{13}$ 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.