Surface structure and field emission property of carbon nanotubes grown by radio-frequency plasma-enhanced chemical vapor deposition

Abstract

In this study, large-area and low-temperature synthesis of carbon nanotubes on glass substrates with transformer coupled plasma (TCP) type radio-frequency plasma-enhanced chemical vapor deposition (rf PE-CVD) system was performed, and their surface structures and field emission property were analyzed. By varying process conditions such as Ni layer thickness, gas flow rate, NH3 etching time, plasma power, and the distance between rf coil and substrate, the optimum conditions for growing carbon nanotubes were found. Their SEM and TEM images showed that their diameters are ranged from 40 to 80 nm, and they have hollow tube structures. From the FTIR spectrum of carbon nanotubes synthesized in this study, large amount of –CH2 and –CH3 functional groups were detected, and the XPS peak of C1s was split into one main peak and several small peaks, which 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 somewhat different from the samples grown by arc-discharge. The measured field emission current density seems to be sufficient to be used for field emission display and increased with the growth time of carbon nanotubes. With these results and equivalent circuit modeling, bodyemission was confirmed to be a dominant emission mechanism.