Since their discovery in 1991, carbon nanotubes have excited many researchers owing to their amazing electrical and mechanical properties. They have various applications such as tip material for field emission devices and scanning probe microscopy, intercalation material for Li ion battery, storage material for hydrogen gas, and so on. But many technical problems are also remained because it's not easy to control them due to so small size of them. Moreover, to commercialize them would not become active, until the techniques for large-scale and low-cost synthesis are developed. In this study, large-area and low-temperature synthesis of carbon nanotubes on glass substrates with TCP (Transformer Couple Plasma) type rf PE-CVD system was performed, and their surface structures and field emission property were also analyzed.
TCP systems have simple structures but can generate high-density plasma and also large area and uniform processes are possible with them. By varying process conditions such as Ni layer thickness, gas flow rate, $NH_3$ etching time, plasma power, the distance between rf coil and substrate, best conditions for growing carbon nanotubes were found. Their SEM and TEM images showed that their diameters are ranged form 40 nm to 80 nm and they have hollow tube structures.
From the FTIR spectrum of carbon nanotubes synthesized in this study, large amount of $-CH_2$ and $-CH_3$ functional groups were detected and XPS peak of $C_1s$ was split into one main peak and several small peaks and that means the chemical state of carbon atoms is divided. Their surface structures were proposed from the FTIR spectrum and the XPS results and they are thought to be somewhat different from those of arc-discharge samples.
Measured field emission current density seems to be sufficient to be used for field emission display and increased with carbon nanotube growth time. With this results and equivalent circuit modeling, body-emission was confirmed to be dominant emission mechanism.
