Raman spectroscopy of epitaxial graphene on a SiC substrate

TL;DR

This study uses Raman spectroscopy to analyze the structure and substrate interaction of epitaxial graphene on SiC, revealing strain effects and differences in electronic structure based on substrate termination.

Contribution

It provides a detailed model explaining strain origin in epitaxial graphene on SiC and compares electronic properties for different substrate terminations.

Findings

Raman bands of EG blue shift due to substrate-induced compressive strain

Lattice mismatch causes 2.27 GPa compressive stress in graphene

Electronic structures differ significantly between Si- and C-terminated SiC substrates

Abstract

The fabrication of epitaxial graphene (EG) on SiC substrate by annealing has attracted a lot of interest as it may speed up the application of graphene for future electronic devices. The interaction of EG and the SiC substrate is critical to its electronic and physical properties. In this work, Raman spectroscopy was used to study the structure of EG and its interaction with SiC substrate. All the Raman bands of EG blue shift from that of bulk graphite and graphene made by micromechanical cleavage, which was attributed to the compressive strain induced by the substrate. A model containing 13 x 13 honeycomb lattice cells of graphene on carbon nanomesh was constructed to explain the origin of strain. The lattice mismatch between graphene layer and substrate causes the compressive stress of 2.27 GPa on graphene. We also demonstrate that the electronic structures of EG grown on Si and C terminated SiC substrates are quite different. Our experimental results shed light on the interaction between graphene and SiC substrate that are critical to the future applications of EG.