Diffraction paradox: An unusually broad diffraction background marks high quality graphene

Date
2019-10-15
Authors
Chen, Shen
Horn-von Hoegen, Michael
Thiel, Patricia
Tringides, Michael
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Ames Laboratory
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Physics and Astronomy
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Chemistry
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Ames LaboratoryPhysics and AstronomyMaterials Science and EngineeringChemistry
Abstract

The realization of the unusual properties of two-dimensional (2D) materials requires the formation of large domains of single-layer thickness, extending over the mesoscale. It is found that the formation of uniform graphene on SiC, contrary to textbook diffraction, is signaled by a strong bell-shaped component (BSC) around the (00) and G(10) spots (but not around the substrate spots). The BCS is also seen on graphene grown on metals, because a single uniform graphene layer can be also grown with large lateral size. It is only seen by electron diffraction but not with x-ray or He scattering. Although the origin of such an intriguing result is unclear, its presence in the earlier literature (but never mentioned) points to its robustness and significance. A likely mechanism relates to the the spatial confinement of the graphene electrons, within a single layer. This leads to large spread in their wave vector which is transferred by electron-electron interactions to the elastically scattered electrons to generate the BSC.

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