Effect of pretreatment on the deposition of carbon nanotubes by using atmospheric-pressure plasma-enhanced chemical-vapor deposition

In this study, carbon nanotubes were grown on NiCr(10 nm)/Cr(100 nm)/glass substrates by using atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) with acetylene (C ₂H ₂) as the carbon source gas at 400 °C, and the effects of pre-treatment, such as annealing at 400 °C in N ₂ and an NH ₃/He plasma treatment, on the growth characteristics of the carbon nanotubes were investigated. Carbon nanotubes were grown only on the samples treated with the NH ₃/He plasma; nearly no carbon nanotubes were grown on the as-deposited samples or on the on the samples annealed at 400 °C in N ₂. The carbon nanotubes grown on the sample treated with the NH ₃/He plasma appear to be related to enhanced carbon diffusion to the Ni catalyst particles because its the cleaner Ni surface to be cleaner than that of the annealed sample and Ni surface area with nanosized Ni particles is larger than that of the as-deposited sample. Because the grown carbon nanotubes were multi-walled carbon nanotubes with defects on the walls. The inner diameters of the grown carbon nanotubes were 3 - 5 nm, and the outer diameters were 20 - 40 nm.