High Layer Uniformity of Two-Dimensional Materials Demonstrated Surprisingly from Broad Features in Surface Electron Diffraction

Paradoxically a very broad diffraction background, named the Bell-Shaped-Component (BSC), has been established as a feature of graphene growth. Although the BSC has been present in the earlier literature it has been ignored. Recent diffraction studies as a function of electron energy have shown that the BSC is not related to scattering interference. The BSC is a very strong effect, but its origin is still unclear. Here, additional experiments are carried out as a function of temperature while monitoring changes in the intensity of different spots over the range that single-layer-graphene (SLG) grows. Quantitative fitting of the profiles shows that the BSC follows the increase of the G(10) spot, proving directly that BSC is an indicator of high quality graphene. Additional metal deposition experiments provide more information about the BSC. The BSC is insensitive to metal deposition and it increases with metal intercalation, because a more uniform interface forms between graphene and SiC. These experiments support the conclusion that the BSC originates from electron spatial confinement within SLG and surprisingly it is an excellent measure of graphene uniformity, instead of film disorder