Three-Fold Diffraction Symmetry in Epitaxial Graphene and the SiC Substrate

TL;DR

This study investigates the crystallographic symmetries and stacking domain distributions in epitaxial graphene on SiC using LEED and LEEM, revealing three-fold and six-fold symmetries linked to different graphene layer configurations.

Contribution

It provides detailed symmetry analysis of graphene layers on SiC, highlighting the complex periodicity and stacking order through diffraction techniques.

Findings

Graphene from 2-3 layers shows 3-fold symmetry consistent with Bernal stacking.

Buffer layer and monolayer graphene exhibit apparent 6-fold symmetry.

Satellite spots indicate complex periodicity in graphene sheets.

Abstract

The crystallographic symmetries and spatial distribution of stacking domains in graphene films on SiC have been studied by low energy electron diffraction (LEED) and dark field imaging in a low energy electron microscope (LEEM). We find that the graphene diffraction spots from 2 and 3 atomic layers of graphene have 3-fold symmetry consistent with AB (Bernal) stacking of the layers. On the contrary, graphene diffraction spots from the buffer layer and monolayer graphene have apparent 6-fold symmetry, although the 3-fold nature of the satellite spots indicates a more complex periodicity in the graphene sheets.