Carbon nanotube growth mechanisms

Abstract

This chapter reviews the growth mechanisms of carbon nanotubes (CNTs). A brief overview of CNT synthesis methods including arc discharge, laser ablation, and chemical vapor deposition (CVD) is first provided, followed by a more in-depth discussion of the CVD method, which is currently the most important technique for CNT growth. The growth models of CNTs in the early stages for these synthesis methods are presented, and the various growth modes that are commonly used to describe CNT growth by CVD are introduced. Comparisons of tip growth vs. root growth, vapor-liquid-solid mode vs. vapor-solid-solid mode, and tangential mode vs. perpendicular mode are provided. Next, focusing on single-walled carbon nanotube (SWCNT) growth by CVD, the growth process of a SWCNT from a catalyst particle is described in detail. Theoretical simulations and in situ experimental analysis performed to elucidate the growth process of SWCNTs are reviewed and compared. In particular, focusing on the physical and chemical states of catalyst particles during SWCNT growth, the current understanding of the growth mechanism is summarized. Finally, the important issue of selective growth of SWCNTs, which can enable the growth of CNTs with desirable properties, is covered. Some important topics related to CNT growth such as vertically and horizontally aligned growth and the effect of a support layer on the catalyst activity are also discussed.