Experimental study of a pulsed microwave plasma assisted chemical vapour deposition of carbon nanotubes

In this study we present the first results achieved on the growth of carbon nanotubes (CNT) in both continuous mode (CM) and pulsed mode (PM) microwave plasma assisted chemical vapour deposition (MPACVD). The interest of this work is to determine the influence of the discharge parameters on the CNT properties such as diameter, length, density... etc. The experiments were carried out at a sustrate temperature around 900 degrees C. The catalyst used was nanostructured Fe-SiO deposited on silicide. It was found that the formation of multiwalls carbone nanotubes (MWCNTs) occurs when varying the discharge parameter from the CM to the PM and a selective growth of bundles of MWCNTs is obtained in the optimal PM plasma mode conditions. The measured diameter of isolated MWCNTs in the CM is around 20 nm. We measured a decrease of the amorphous carbon structures by a factor 7 and an increase of the CNT density by a factor 3 from the CM to the PM, confirming that the pulsed mode is more suitable for the MWCNT growth.