Patterned growth of carbon nanotube forests using Cu and Cu/Ag thin film reservoirs as growth inhibitors

Lithography and lift-off of the catalyst is the established way to pattern forests of carbon nanotubes (CNTs). We demonstrate an alternative technique where we pattern a thin film reservoir residing below the Al2O3 underlayer to partially or fully deactivate the iron catalyst on the surface, thus leading to short CNTs or no CNTs. High-resolution imaging suggests that mass transfer from the Cu or Cu/Ag alloy reservoir to the surface promotes interalloying with the catalyst, which is the mechanism for deactivation. The lower melting temperature of the Cu/Ag alloy is more effective than Cu in inhibiting CNT growth since it becomes partially liquid at the processing temperature, to faster alloy with the iron catalyst.