Analysis of The Initial Growth Process of Carbon Nanotubes on The Silicon Carbide Surface and Control Their Formation by The Surface Modification

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Silicon carbide (SiC) is a very promising material for applications to high-power and high-frequency devices because of its large breakdown field and high electron mobility. In addition, it is interesting that the energy band-gap of SiC is rather wide and shows different values depending on its own crystallographic structures: hexagonal, rhombohedral or cubic. A multilayer structure of the SiC polytypes could become a new material with controllable band-gaps. Moreover, it is expected to be a substrate for heteroepitaxial growth of group III nitrides. Kusunoki et al. have recently reported [Appl.Phys.Lett.77(2000)531] that carbon nanotubes (CNTs) are formed on a 6H-SiC(000-1) surface after annealing the substrate at 1700℃ in a vacuum furnace. There are polar surfaces corresponding to Si-terminated (0001) and C-terminated (000-1) surfaces for 6H-SiC. It is interesting to note that on a 6H-SiC(0001) surface they could not obtain CNTs but only several graphite layers. The initial process of CNT growth on the 6H-SiC(000-1) surface has not been elucidated yet. In the present study, we investigated the initial process of graphitization on the 6H-SiC(000-1) surface and found that graphite layers without grobal coincidence of their crystallographic orientations grew on the 6H-SiC(000-1) surface when annealed at temperatures higher than 1300℃. We also investigated to control the formation of CNTs on the SiC surface by surface modification. When the 6H-SiC(000-1) surface applied the laser followed by annealing at 1700℃, we cannot observe the CNTs on the surface. This result indicated that we can make CNT devices using an idea such as surface modification