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I expect that you are on the right track Red Badger. The solid state physicists at FR are probably too busy designing to weigh in, but there are likely many issues at work, and probably being considered by semiconductor designers before this Graphene layer can become deployed. My guess, given that the performance number given is about 30%, that this is another design rules shrink. Shrinking design rules are constrained by interconnect limitations. The “wires” inside a processor with over 1 1/2 billion transistors, and probably double that number of simple gates, is enormous, probably over 40 billion. The delay through the wires connecting all those devices limits frequencies, since 64 bit registers must have 64 bits all loaded before those registers can be read. When data arrive irregularly it is called “skew”. I’m guessing that Graphene is more important for its thinness and to minimize contamination, since the silicon substrate is an insulator unless it is “contaminated”, accidentally, or intentionally, as in “doped”, the process used to create semiconductors.

Perhaps we have an expert who can correct me or illuminate the issue? Few understand what a wonder our semiconductors are. To add what little else I have encountered measuring electrical signals, the dielectric constant of the insulator has a significant effect upon the velocity of electrical signals through a conductor. We used to estimate electrical pulse velocity at 7 inches/nanoseconds or about 60% of the velocity of light in a vacuum. Today’s semiconductors behave like waveguides, only they are built of millions of waveguides, yes, radio frequencies. These waveguides behave just like those pipes inside radar transmitters and receivers, but carry much less power. If they didn’t, a 4 Gigahertz processor couldn’t work since there would be no way to pass bits between logical units, or even to differentiate ones from zeros.

I’m guessing that Graphene is more important for its thinness and to minimize contamination, since the silicon substrate is an insulator unless it is “contaminated”, accidentally, or intentionally, as in “doped”, the process used to create semiconductors.

The Stanford experiment showed that graphene could perform this isolating role while also serving as an auxiliary conductor of electrons. Its lattice structure allows electrons to leap from carbon atom to carbon atom straight down the wire, while effectively containing the copper atoms within the copper wire.

I'm guessing that the copper 'wires' are functioning really like just a skeletal substructure to hold the graphene's carbon atoms in place. The graphene is really the true conductor, while the copper fills in any 'holes' that may be present in the graphene. With copper atoms being larger than carbon atoms, they cannot migrate thru the holes into the silicon.......................