Aligned millimeter-long carbon nanotube arrays grown on single crystal magnesia

Single crystal magnesium oxide (MgO) was found to be very beneficial to the growth of aligned carbon nanotube (CNT) arrays as long as 2.2 mm by chemical vapor deposition. Before growth, a thin film of catalyst (iron) was coated on the MgO by magnetron sputtering. Scanning electron microscopy was used to study the alignment and length, and transmission electron microscopy was used to exam the wall numbers, diameter, and graphitization. It was found that the number of walls as few as two can be controlled by the catalyst film thickness, whereas the length is a combined result of gas pressure, temperature, and time during growth. Water was found not to be a factor to the length of CNTs grown on MgO, but a significant factor when sapphire was used as the substrates.