STM observation of formation process of carbon nanotube from 6H-SiC (000-1)
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0901-Ra11-13-Rb11-13.1
STM observation of formation process of carbon nanotube from 6H-SiC (000-1) T. Maruyama1,2, Y. Kawamura2, H. Bang1, N. Fujita2, T. Shiraiwa2, K. Tanioku2, Y. Hozumi2, S. Naritsuka1,2 and M. Kusunoki3 1 Meijo Univ. 21st CENTURY COE program “Nano Factory”, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan 2 Department of Materials Science and Engineering, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan 3 Japan Fine Ceramics Center, FCT Central Research Department, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587, Japan ABSTRACT Formation process of nanosized cap structures on a thermally treated 6H-SiC(000-1) substrate was investigated using atomic-resolution ultrahigh-vacuum scanning tunneling microscopy (UHV-STM). After formation of clusters of carobon particles 1-2 nanometer in diameter at 1150°C, these nanoparticles merged, forming nanosized cap structures. Hexagonal carbon networks, partly composed of pentagons, were clearly observed on the surface of the cap structures for a sample annealed above 1200oC. A model for the formation of carbon nanocaps on 6H-SiC(000-1) was proposed. INTORODUCTION Earlier, the synthesis of aligned carbon nanotube (CNT) films on SiC(000-1) substrates was reported by Kusunoki et al. in our group.1 By this method, aligned zigzag-type CNTs with fairly uniform tube diameters can be selectively produced only by heating at sufficient high temperature in a vacuum electric furnace.2 They investigated the formation mechanism of CNT on SiC C-face by high-resolution transmission electron microscopy (HRTEM) and showed that nanosized cap structures appear at the initial stage of CNT formation.3 However, the formation process of carbon nanocaps has never been sufficiently clarified, although it most likely determines the structure of the final CNT grown. In this study, we observed cap structures formed on a thermally treated 6H-SiC(000-1) substrate in a vacuum electric furnace, using ultrahigh-vacuum scanning tunneling microscopy (UHV-STM). We also carried out STM observation for the samples annealed under UHV to suppress surface oxidation during heating, and succeeded in obtaining clear STM images for the formation process of carbon nanocaps on SiC (000-1) surface.
0901-Ra11-13-Rb11-13.2
EXPERIMENTAL DETAILS Commercial single-crystal wafers of 6H-SiC(000-1) (CREE Research, Inc.) cut into 3.0×7.0×0.2 mm3 were dipped in a 10% hydrofluoric acid (HF) solution for 15 min to remove surface oxides. After rinsing by deionized water, the samples were placed in a vacuum electric furnace (
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