Synthesis and applications of single walled carbon nanotubes from ethylene as carbon source

Single walled carbon nanotubes (SWCNTs) as emerging material have great potential, due to their striking structural and electronic properties, for applications in thin film transistors (TFTs), flexible displays and energy conversion. Floating catalyst chemical vapour deposition (FCCVD) has been applied to synthesize SWCNTs from various carbon precursors. Ethylene, as one important carbon source, has been widely used and studied in substrate CVD. However, SWCNT synthesis from ethylene in FCCVD and understanding about the structure and types of the SWCNTs produced are lacking. This dissertation comprehensively explored the growth of SWCNTs in ethylene-FCCVD. Ethylene (0.75 ccm) was first time used as carbon source alone in FCCVD along with 40 ccm hydrogen and 300 ccm nitrogen as the carrier gas. The whole growth process is environmental friendly and economical for scale-up production of nanotubes. Ethylene based FCCVD produced 1.50 nm mean diameter nanotubes. Electron diffraction shows random chirality distribution of SWCNTs between the armchair and zigzag edge. Moreover, the structure of nanotubes was further tuned with the introduction of water as a promoter. Optimum water concentration of 115 ppm reduced the mean diameter of the tubes to 1.10 nm and extremely narrow chirality distributed tubes were synthesized. The accumulation of single chirality (9,8) approaches to 27% of the tubes. The further studies also showed water can influence the formation of nanoparticles (NPs) in the gas phase, which might be the reason for SWCNT structure regulation in FCCVD. Furthermore, the transparent conducting films (TCFs) of SWCNTs were fabricated, based on ethylene-FCCVD. The TCFs consisting of highly individual SWCNT with length up to 13 μm, possesses high conductivity with sheet resistance as low as 51 Ohm/sq. for 90% transmission, which is one of the lowest sheet resistance value reported for SWCNT TCFs. In comparison, TCFs were also produced with same process, but with CO as carbon source. Due to bundling and short nanotubes, the SWCNT TCFs from CO has a higher sheet resistance of 89 Ohm/sq. for 90% transmission. Specifically, simultaneous growth of SWCNT and graphene was observed in ethylene-based FCCVD. It is believed that oversupply of carbon from ethylene decomposition assists the growth of graphene. In addition, the novel hybrid structure of 1D SWCNTs and 2D graphene was also fabricated. The interface of nanotubes and graphene hybrid showed carbon-carbon alignment spanning hundreds of nanometers.