Carbon nanotubes (CNTs) is one of the most interesting materials in nanotechnology and nanodevices, because of their superior structural, mechanical, chemical, thermal, and electrical performance. Kusunoki at al. have reported the surface decomposition method to anneal SiC surface as one of the methods of generating CNTs [1]. High density, high alignment and the zig-zag type CNTs are obtained by this method [2]. As the catalyst is not used, impurities do not mix with CNTs during growth process. It is thought that surface morphology, density of defect, annealing temperature, atmosphere around surface and heating rate, etc. influences CNTs generation when CNTs is formed by the surface decomposition. We have study that the morphology of the graphite layers on the SiC(000-1) surface influences the CNT growth. We have reported that there appear many protrusions, which might be precursor of CNTs, in the domain boundary of the graphite after annealing in the UHV [3].
In this study, we investigated the effect of the heating rate upon the formation of CNTs on the SiC(000-1) surface.
The samples were heated to 1700oC at the heating rate of 20 - 400 °C/min, and held at the temperature for 1 h. Their cross sections were observed by TEM using 300kV electron beams. When the heating rate is slow, we observed CNTs on the SiC(000-1) surface. However, when the heating rate exceeds 400 °C/min, the amorphous layer is formed on the interface of CNTs and the SiC substrate.
[1]M.Kusunoki, M.Rokkaku and T.Suzuki: Appl.Phys.Lett., 71(1997), 2620-2622.
[2]M.Kusunoki, T.Suzuki, C.Honjo, T.Hirayama and N.Shibata: Chem.Phys.Lett., 366(2002), 458-462.
[3]T.Yamauchi, T.Tokunaga, M.Naitoh, N.Toyama, S.Nishigaki, F.Syoji and M.Kusunoki: Surf.Sci., 600(2006), 4077-4080. |