Sustained growth of ultralong carbon nanotube arrays for fiber spinning

A catalysts structure consisting of a thin Fe film on a dense Al ₂O₃ buffer layer that was deposited on Si substrate by IBAD (ion-beam assisted deposition) was investigated for sustained growth. The catalysts usually become inactive within several minutes due to either interdiffusion with the substrate or the accumulation of amorphous carbon in CVD process. In order to achieve sustained growth, catalysts like ferrocene have been added continuously or intermittently into the system to nucleate new catalyst particles during the growth. It has been found that the Al ₂O₃ layer deposited by the IBAD technique was mostly amorphous and denser than those deposited by other techniques. Raman spectroscopy revealed that CNT arrays grown with water vapor had less amorphous carbon than those grown without water vapor.