The structural properties of the multi-layer graphene/4H-SiC(000-1) system as determined by Surface X-ray Diffraction

TL;DR

This study uses Surface X-Ray Reflectivity to analyze the structure of multi-layer graphene on 4H-SiC(000-1), revealing a strong substrate bond and near turbostratic growth mode, challenging previous assumptions about weak Van der Waals interactions.

Contribution

First direct measurement of the graphene-substrate bond length on 4H-SiC(000-1), showing strong bonding and turbostratic growth mode of multilayer graphene.

Findings

Graphene-substrate bond length is 0.162nm, indicating strong bonding.

Multi-layer graphene grows in a near turbostratic mode.

Results explain the lack of broken symmetry in conduction measurements.

Abstract

We present a structural analysis of the multi-layer graphene-4HSiC(000-1}) system using Surface X-Ray Reflectivity. We show for the first time that graphene films grown on the C-terminated (000-1}) surface have a graphene-substrate bond length that is very short (0.162nm). The measured distance rules out a weak Van der Waals interaction to the substrate and instead indicates a strong bond between the first graphene layer and the bulk as predicted by ab-initio calculations. The measurements also indicate that multi-layer graphene grows in a near turbostratic mode on this surface. This result may explain the lack of a broken graphene symmetry inferred from conduction measurements on this system [C. Berger et al., Science 312, 1191 (2006)].