Aerosol synthesis of single-walled carbon nanotubes by tuning feeding flow configuration for transparent conducting films

The diameter, bundle length, and bundle diameter of single-walled carbon nanotubes (SWCNTs) are key factors to their thin-film conductivity. Whereas these parameters interact and evolve simultaneously during SWCNT growth. Thus it is challenging to study the effect of one parameter solely on thin-film conductivity. Herein, we synthesized SWCNT samples with controllable shapes by simply modulating the flow rate of gases using floating catalyst chemical vapor deposition (FCCVD), where the carbon monoxide is served as the carbon source (CO) and ferrocene as catalyst precursor. By varying CO flow rates through ferrocene and the quartz tube, we obtained SWCNT samples with the constant mean tube diameter, while the bundle diameter or bundle length differs from each other. As a result, the SWCNT thin films exhibit tunable sheet resistance, in which the film with the bundle length of 16 μm and bundle diameter of 4.8 nm presents the lowest sheet resistance (84 Ω/□ at 90% transmittance by AuCl₃ doping). Differing from the conventional methods, such as modulating temperature or catalyst size, our facile approach of regulating gas flow rates offers a new option for the controlled synthesis of SWCNTs.