Etch track-directed growth of carbon nanotubes on graphite

Highlights: • Crystallographically-oriented nanotubes are grown on highly-etched graphite surfaces. • Nanotubes adhere to the etch tracks, orienting them along the graphite zigzag directions. • Nanomaipulation shows that nanotubes adhere to the top surfaces of few-layer graphene step edges. • Proposed possible strain modes of graphene edge adhesion to nanotubes. Crystallographically-oriented nanotubes are grown on highly-etched graphite surfaces. The nanotubes are found to align along preferred crystal directions of the graphite surface along the same directions as etch tracks. This indicates that the nanotubes adhere to the etch tracks, which are themselves oriented along the three zigzag directions of the graphite surface. This nanotube adhesion to etch tracks is supported by nanotubes that are observed to grow on top of and adjacent to the etch tracks. The adhesion of nanotubes adjacent to etch tracks suggests that strain modes at the vicinity of exposed graphene edges may allow for a lower free energy for nanotubes to be located at these locations. Direct evidence of this adhesion of nanotubes to the tops of graphene step edges is observed through their nanomanipulation. These results demonstrate that a greater net load is required to dislodge a nanotube from an edge than is needed to drag the same tube to that edge.