Effect of temperature and role of Mo top layer on the growth of carbon nanotubes

T A Nguyen, P T H Nguyen, D H Dinh, M C Dang, W Song, D Jung, S K Kim and C Park

Abstract

Carbon nanotubes (CNTs) were synthesized by a thermal chemical vapor deposition method using a three-layer Al/Fe/Mo metal catalyst. All metal layers were deposited by dc sputtering. With a scanning electron microscope (SEM) and Raman spectra, we investigated the effect of temperature and the role of the Mo top layer on the structure and quality of grown CNTs. The results showed that the growth temperature was an important parameter for the synthesis of CNTs. With an Al/Fe/Mo triple layer catalyst, the role of the Mo top layer was as the barrier layer to control the diameter, density and the peak intensity ratio of the G-peak to D-peak (I_G/I_D) of the CNTs. These results indicate that the thickness of the Mo top layer increased, which leads to decrease of the density of the CNTs. In the case of Mo 5 nm, the radial breathing mode (RBM) of the CNTs was observed in Raman spectra at 250 cm⁻¹ and corresponds to the single-wall carbon nanotube with 0.95 nm diameter.