Diamond (111) surface reconstruction and epitaxial graphene interface

The evolution of the diamond (111) surface as it undergoes reconstruction and subsequent graphene formation is investigated with angle-resolved photoemission spectroscopy, low energy electron diffraction, and complementary density functional theory calculations. The process is examined starting at the C(111)-(2×1) surface reconstruction that occurs following detachment of the surface adatoms at 920°C, and continues through to the liberation of the reconstructed surface atoms into a freestanding monolayer of epitaxial graphene at temperatures above 1000°C. Our results show that the C(111)-(2×1) surface is metallic as it has electronic states that intersect the Fermi level. This is in strong agreement with a symmetrically π-bonded chain model and should contribute to resolving the controversies that exist in the literature surrounding the electronic nature of this surface. The graphene formed at higher temperatures exists above a newly formed C(111)-(2×1) surface and appears to have little substrate interaction as the Dirac point is observed at the Fermi level. Finally, we demonstrate that it is possible to hydrogen-terminate the underlying diamond surface by means of plasma processing without removing the graphene layer, forming a graphene-semiconductor interface. This could have particular relevance for doping the graphene formed on the diamond (111) surface via tuneable substrate interactions as a result of changing the terminating species at the diamond-graphene interface by plasma processing.