Tube number density control of carbon nanotubes on anodic aluminum oxide template

Abstract

We demonstrate that the tube number density of well-aligned carbon nanotubes (CNTs) grown over the nanoporous anodic aluminum oxide (AAO) template can be directly controlled by adjusting the CH 4/H 2 feed ratio during the CNT growth in a microwave plasma electron cyclotron resonance chemical vapor deposition (ECR-CVD) system. During the CNT growth, the nanotube growth and the amorphous carbon deposition on the AAO pore wall take place simultaneously. The amorphous carbon sediment will gradually cover up the AAO nanopores and prevent the nanotubes to grow out of the nanopores. By adjusting the CH 4/H 2 feed ratio, one can control the amount of the deposited amorphous carbon and thus the number of CNTs grown over the AAO nanopores. It was found that the CNT density decreases linearly with increasing the CH 4 concentration. The CNT density decreased by a factor of about 4.5 when the CH 4 concentration increased from 9% to 91%.