Thickness effect of nanosized thin-film iron dot on growth of multiwall carbon nanotubes

Hot-filament chemical vapor deposition, using a mixture of methane and hydrogen, is used to grow micrometer-long multiwall carbon nanotubes (MWNTs) on 1-μm -diametric iron dots with thicknesses of 54, 40, and 20 nm. Bunches of MWNTs grow on the nanosized thin-film iron dots, and thicker iron dots have more MWNTs, because the nanosized thin-film iron dot behaves as a thin film with many catalyst nanoparticles rather than as a catalyst surface. Therefore, the thickness of the nanosized thin-film iron dot strongly dominates the MWNT growth. However, the MWNTs growing on the iron dots are 1 μm long and ~90 nm wide, indicating that the length and diameter of the MWNT are independent of the size and thickness of the iron dot. In addition, the effect of the applied electrical field on the growth of MWNTs is presented.