  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)-(2x1) surface reconstruction that occurs following detachment of the
surface adatoms at 920 {\deg}C, and continues through to the liberation of the
reconstructed surface atoms into a free-standing monolayer of epitaxial
graphene at temperatures above 1000 {\deg}C. Our results show that the
C(111)-(2x1) surface is metallic as it has electronic states that intersect the
Fermi-level. This is in strong agreement with a symmetrically {\pi}-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\times1)
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.
