The interface structure of epitaxial graphene grown on 4H-SiC(0001)

TL;DR

This study uses surface x-ray reflectivity to analyze the structure of the graphene-4H-SiC(0001) interface, revealing an extended reconstruction of SiC bilayers and detailed interlayer distances that differ from graphite and previous predictions.

Contribution

It provides the first detailed structural characterization of the epitaxial graphene interface on 4H-SiC(0001) using surface x-ray reflectivity.

Findings

The interface consists of an extended reconstruction of two SiC bilayers.

The interface layer is more than twice the thickness of a bulk SiC bilayer.

The distance from the interface to the first graphene sheet is smaller than graphite interlayer spacing.

Abstract

We present a structural analysis of the graphene-4HSiC(0001) interface using surface x-ray reflectivity. We find that the interface is composed of an extended reconstruction of two SiC bilayers. The interface directly below the first graphene sheet is an extended layer that is more than twice the thickness of a bulk SiC bilayer (~1.7A compared to 0.63A). The distance from this interface layer to the first graphene sheet is much smaller than the graphite interlayer spacing but larger than the same distance measured for graphene grown on the (000-1) surface, as predicted previously by ab intio calculations.