Structural and electronic properties of Li intercalated graphene on SiC(0001)

TL;DR

This study combines experimental and theoretical methods to analyze how lithium intercalation affects the structure and electronic properties of graphene on SiC, revealing ordered intercalation and modifications to the electronic band structure.

Contribution

It provides new insights into the atomic arrangement and electronic effects of Li intercalation in graphene on SiC, including the formation of ordered structures and band modifications.

Findings

Li intercalates at room temperature at specific interfaces

Li intercalation causes strong n-doping of graphene

Intercalated Li induces band structure changes similar to C6LiC6

Abstract

We investigate the structural and electronic properties of Li-intercalated monolayer graphene on SiC(0001) using combined angle-resolved photoemission spectroscopy and first-principles density functional theory. Li intercalates at room temperature both at the interface between the buffer layer and SiC and between the two carbon layers. The graphene is strongly $n$-doped due to charge transfer from the Li atoms and two $\pi$-bands are visible at the $\bar{K}$-point. After heating the sample to 300$^\circ$C, these $\pi$-bands become sharp and have a distinctly different dispersion to that of Bernal-stacked bilayer graphene. We suggest that the Li atoms intercalate between the two carbon layers with an ordered structure, similar to that of bulk LiC$_6$. An AA-stacking of these two layers becomes energetically favourable. The $\pi$-bands around the $\bar{K}$-point closely resemble the calculated band structure of a C$_6$LiC$_6$ system, where the intercalated Li atoms impose a super-potential on the graphene electronic structure that opens pseudo-gaps at the Dirac points of the two $\pi$-cones.