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

碳化硅具有较大的击穿电场和较高的电子迁移率，是一种非常有前途的高功率高频器件材料。此外，有趣的是，碳化硅的能带隙很宽，并根据其晶体结构的不同而表现出不同的值：六方结构、三方结构或立方体结构。碳化硅多型体的多层结构有望成为一种带隙可控的新材料。此外，它有望成为III族氮化物异质外延生长的衬底。Kusunoki等人。最近[Appl.Phys.Lett.77(2000)531]报道，在真空炉中1700℃的温度下，在6H-SiC000-1的表面上形成了碳纳米管(CNT)。对于6H-碳化硅，存在与Si端面(0001)和C端面(000-1)相对应的极性表面。有趣的是，在6H-SiC(0001)表面上，它们不能得到碳纳米管，而只有几层石墨层。碳纳米管在6H-碳化硅(000-1)表面生长的初始过程尚未阐明。在本研究中，我们研究了6H-SiC(000-1)表面的石墨化初始过程，发现在高于1300℃的温度下，在6H-SiC(000-1)表面上生长的石墨层与其晶体取向没有全局一致。我们还研究了通过表面改性来控制碳化硅表面碳纳米管的形成。6H-SiC(000-1)表面经1700℃激光处理后，未观察到碳纳米管的存在。这一结果表明，利用表面改性的思想可以制作碳纳米管器件

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