The authors characterize the detailed interface structure of Ni-catalyzed vertically aligned carbon nanofibers (CNFs) prepared by plasma-enhanced chemical vapor deposition for interconnect applications. Stacked graphitic layers and cup-shape structures of CNFs around the interface region have been observed using high-resolution scanning transmission electron microscopy. The interaction between the Ni catalyst and Ti layer dramatically affects the CNF structure during initial growth. The effect of interface nanostructures on contact resistance is also discussed.