Is electron transport in nanocrystalline Cu interconnects surface dominated or grain boundary dominated?

Through controlled numerical experiments using first principles density functional theory based electron transport, we find that surface effects can dominate electron transport in nanocrystalline Cu interconnects, even in transport regimes that have been interpreted as grain boundary dominated. We find that the role of the surface relative to that of the grain boundaries is sensitive to the degree of Grain Orientation Anisotropy. The implications for interconnect resistance engineering are also discussed.