  High-quality, large-area epitaxial graphene can be grown on metal surfaces
but its transport properties cannot be exploited because the electrical
conduction is dominated by the substrate. Here we insulate epitaxial graphene
on Ru(0001) by a step-wise intercalation of silicon and oxygen, and the
eventual formation of a SiO$_2$ layer between the graphene and the metal. We
follow the reaction steps by x-ray photoemission spectroscopy and demonstrate
the electrical insulation using a nano-scale multipoint probe technique.
