Fig. 7

Different growth mechanisms of CNTs using CVD (Adapted from [101]). Based on the catalyst-substrate interactions, two types of CNT growth mechanics can be seen. aTip-growth model: with weak catalyst-substrate interactions, a tip-growth is observed where hydrocarbon decomposes on top surface of the metal that causes carbon to diffuse downwards through the metal leading to CNTs growing out from the bottom of the metal. b Base-growth model: With strong catalyst-substrate interactions, a base-growth is observed where CNTs grow out of the metal far from the substrate while the catalyst is rooted at the base