  The formation of graphene on the (0001) surface of SiC (the Si-face) is
studied by atomic force microscopy, low-energy electron microscopy, and
scanning tunneling microscopy/spectroscopy. The graphene forms due to
preferential sublimation of Si from the surface at high temperature, and the
formation has been studied in both high-vacuum and 1-atm-argon environments. In
vacuum, a few monolayers of graphene forms at temperatures around 1400 C,
whereas in argon a temperature of about 1600 C is required in order to obtain a
single graphene monolayer. In both cases considerable step motion on the
surface is observed, with the resulting formation of step bunches separated
laterally by >10 microns. Between the step bunches, layer-by-layer growth of
the graphene is found. The presence of a disordered, secondary graphitic phase
on the surface of the graphene is also identified.
