Plasma ablation enhanced chemical vapor deposition

The VLS synthesis requires only the presence of a metaUic catalyst and nanowire material in the vapor. Consequently, a broad spectrum of VLS-based techniques has been developed for synthesizing nanowires. Here, only the three primary techniques will be described, namely, flow reaction, laser ablation and CVD, which indudes plasma-enhanced chemical vapor deposition (PECVD). However, the primary focus will be on CVD-based techniques utUized in the authors laboratory. 

The first MWNTs have been obtained as early as 1976 by iron-catalyzed pyrolysis of benzene. Apart from that, there is a number of methods to produce MWNT, which all of them differ in the way of generating small carbon clusters or atoms from the respective starting materials. They include arc discharge, laser ablation, chemical vapor deposition with and without plasma enhancement or the catalytic decomposition of various precursor compounds. It turned out that MWNTs from low-temperature syntheses bear more defects and, as a whole, are less ordered than those generated at high temperatures. However, these drawbacks can still be compensated by subsequent recuperation of defective samples at elevated temperatures. 

Nanoparticles can be produced by several methods including mechanical, electric arc discharge, laser ablation, chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD) and wet chemical reactions. 

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