A diffraction paradox: An unusually broad diffraction background signals ideal graphene

TL;DR

This paper reveals that a broad diffraction background, observed via electron diffraction, indicates the formation of ideal, large-domain graphene on various substrates, due to electron confinement effects.

Contribution

It identifies a unique diffraction feature, the bell-shaped component, as a signature of ideal graphene formation, highlighting the role of electron confinement in diffraction patterns.

Findings

The bell-shaped component appears around specific diffraction spots for ideal graphene.

This feature is observed only in electron diffraction, not X-ray or He-scattering.

Electron confinement causes a broadening in wavevector transfer, producing the BSC.

Abstract

The realization of the unusual properties of 2-d materials requires the formation of large domains of single layer thickness, extending over the mesoscale. It is found that the formation of ideal graphene on SiC, contrary to textbook diffraction , is signaled by a strong bell-shaped-component (BSC) around the (00) and G(10), but not the SiC(10) spots.The BSC is also seen for graphene on metals, because single layer uniform graphene with large lateral size can also be grown. It is only seen by electron diffraction and not with X-ray or He-scattering experiments. Most likely it originates from the spatial confinement of the graphene electrons within a single layer. This leads to a large spread in their wavevector, which is transferred through electron-electron interactions to the elastically scattered electrons to generate the BSC.