Vertically-aligned carbon nanotube at low pressure by cold-wall thermal CVD using a two-phase deposition step

Abstract

This paper reports a new method to grow vertically-aligned carbon nanotubes (VA-CNT) in a cold-wall system, using a two-phase deposition step at low pressure. The first phase consists of the flow of NH3 for a short period together with the C2H2 flow to ensure catalyst activation. In the second phase, NH3 flow is replaced by H2 flow during the remaining growth time, to obtain tall VA-CNT. Previous tests with only one of the reduction gases flowing with C2H2 during the deposition step demonstrated that the NH3 flow contributes to increasing the VA-CNT uniformity throughout the substrate, while the H2 flow contributes to obtaining taller VA-CNT. The conclusions drawn during these tests lead to the recipe with a two-phase deposition step. The VA-CNT obtained with this new recipe reached a maximum height of 160 µm and a non-uniformity of 21.9 %, which falls within the state-of-the-art values. Furthermore, this process takes place at low pressure and only the chamber stage is heated, which allows a cheaper production of this material on a large scale.