Controlled Growth of Single‐Walled Carbon Nanotube Networks by Catalyst Interfacial Diffusion

Single‐walled carbon nanotubes are promising for many applications due to their unique mechanical, electrical and optical properties. However, their application has been hampered so far by the lack of controllability in the direct growth process, in particular the size and chirality distributions which inevitably lead to a large variability of their electronic structures. Here we demonstrate the effect of catalyst interfacial diffusion using a tri‐layered Al₂O₃/Fe(Mo)/Al₂O₃ catalyst and achieve the effective control of density, diameter, and conductivity of the as‐grown nanotube networks. This method modulates the thickness of the top Al₂O₃ layer which affects the diffusion of Fe atoms and subsequently the formation of catalyst nanoparticles. We show that the tri‐layered catalyst allows one to vary the density of networks from 0.18 to 35 tubes/μm², the diameter from 1.36 to 1.72 nm, and the metallic fraction from 20% to 45%. It may thus represent a promising strategy for tailoring the properties of as‐grown carbon nanotube networks for their proposed applications.