Nucleation and growth of carbon nanotubes by microwave plasma chemical vapor deposition

The nucleation and growth of aligned multiwall carbon nanotubes by microwave plasma-enhanced chemical vapor deposition have been studied. The nanotubes nucleate and grow from catalytic cobalt islands on a silicon substrate surface, with both their diameter and length dependent on the size of the cobalt islands. Electron microscopy reveals that the nanotubes grow via a “base growth” mechanism. The nanotubes grow initially at a very rapid and constant rate (∼100 nm/s) that decreases sharply after the catalyst Co particles become fully encapsulated by the nanotubes. We propose a detailed model to explain these experimental observations on nucleation and growth of nanotubes.