We have investigated the pretreatment effects of nitrogen on the length and the alignment of carbon nanotubes (CNTs) grown on a Ni catalyst by using dc-plasma enhanced chemical vapor deposition system. The surface of the Ni catalyst was pretreated with a mixture of NH₃ and N₂, instead of pure NH₃ and the length of the CNTs has changed from 1.6 μm to 400 nm as the NH₃/N₂ flow rate ratio was decreased. We showed that the length and the alignment of the CNTs could be controlled by changing the NH₃/N₂ flow rate ratio. The fabricated CNTs were further evaluated by using their Raman spectra. The nitrogen concentration on the surface of the Ni catalyst after the pre-treatment was analyzed by using X-ray photoelectron spectroscopy and the physical structure of CNTs was analyzed using scanning electron microscopy and high resolution transmission electron microscope. We suggest that the N₂ adsorption on the surface of Ni changes the carbon atom diffusion during the CNT growth and that the physical structures of CNTs are drastically changed.

Duy D.Q., Kim H.S., Yoon D.M., Ha J.W., Lee K.J., Hwang Y.G., Lee C.H., Cong B.T.

366.pdf    Gửi cho bạn bè

Từ khóa :