Effect of oxygen plasma alumina treatment on growth of carbon nanotube forests

We use oxygen plasma to increase the height of forests from ∼0.2 to >2 mm. The effectiveness of treating alumina by oxygen plasma, prior to iron nanoparticle formation, is studied using cycles of nanotube growth, nanotube burning, and regrowth. This demonstrates that plasma-treated alumina is more resistant to iron bulk diffusion than an untreated one. Secondary ion mass spectroscopy shows there is negligible iron diffusion into the bulk of treated alumina. Plasma treatment of catalyst supports is potentially useful for growth of ultra-high-density nanotube forests for applications such as interconnects in integrated circuits and heat sinks.