Evolution in Catalyst Morphology Leads to Carbon Nanotube Growth Termination

A mechanism by which catalyst deactivation occurs during vertically aligned single-walled carbon nanotube (SWNT) growth is demonstrated. We have used both quantitative measurements of nanotube growth rates and ex situ and in situ transmission electron microscopy observations to show that termination of carbon nanotube (CNT) array growth can be intrinsically linked to evolution of the catalyst morphology. Specifically, we find that a combination of both Ostwald ripening and subsequent subsurface diffusion leads to loss of the Fe catalyst, and through direct observations, we correlate this with nanotube growth termination. These observations indicate that careful design of the catalyst and its support − as well as the interaction between the two − is required to maximize nanotube yields.