Film Formation from Vapor Phase by CVD

In most CVD processes the CVD material is formed on the surface of the substrate, but in some cases the substrate can react with a deposit to form a compound. Conventionally, the CVD method is performed in the presence of transition metal catalyst particles supported on a substrate. The CVD method enables the selective production of MWCNTs or SWCNTs, depending on the reaction chemistry and process parameters, such as temperature. Furthermore, pre-determined CNT structures can be formed via catalyst patterning on the substrate [see, e.g., 49-51]. Alternatively, the catalytic CNT synthesis can be performed in the gas phase without support material [52, 53]. 

The gas-phase synthesis of SWCNTs has been coupled on a few occasions with product collection directly from the gas phase, e.g., with filters and cold collectors [52]. More commonly, the product is collected from the reactor surfaces after cooling. This, however, allows catalyst nanoparticle and SWCNT nueleation and growth at the reaetor surfaces in a maimer similar to the supported CVD method. 

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