Junctions of Carbon Nanotubes and Silicon Nanowires Synthesized by ethanol-Co Chemical Vapor Deposition
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0963-Q10-08
Junctions of Carbon Nanotubes and Silicon Nanowires Synthesized by ethanol-Co Chemical Vapor Deposition Hideto Yoshida1, Tetsuya Uchiyama1, Jun Kikkawa2, Seiji Takeda1,3, and Yoshikazu Homma3,4 1 Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka, 560-0043, Japan 2 Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science, 1-8-31 Midorigaoka, Ikeda, Osaka, 563-8577, Japan 3 CREST, Japan Science and Technology Agency, Kawaguchi, Saitama, 332-0012, Japan 4 Department of Physics, Tokyo University of Science, Shinjuku-ku, Tokyo, 162-8601, Japan ABSTRACT Carbon nanotubes (CNTs) have been grown on silicon nanowires (SiNWs) by chemical vapor deposition using Co catalyst nanoparticles. Single-walled CNTs have been grown mainly when a thin Co film (0.1 nm thick) was deposited on SiNWs, while both SWNTs and MWNTs have been grown on SiNWs on which Co 0.5 nm thick was deposited. The correlation between the diameter of catalyst nanoparticles and that of CNTs has been investigated by transmission electron microscopy. The average diameter of CNTs is smaller than that of catalyst nanoparticles. INTRODUCTION Both carbon nanotubes (CNTs) [1,2] and silicon nanowires (SiNWs) [3-5] are promising nanomaterials as building blocks of future nanodevices. Moreover, heterojunctions of these materials have a great potential as new devices, for example a nanoscale Schottky diode and a nanoscale light emitting diode. Junctions of multi-walled carbon nanotubes (MWNTs) and SiNWs have been synthesized by chemical vapor deposition (CVD) and exhibit rectifying behaviour [6]. In this paper, we show that single-walled CNTs (SWNTs) and MWNTs can be grown on SiNWs by CVD using ethanol as a carbon source and Co nanoparticles as catalysts. We investigate the correlation between the diameter of catalyst nanoparticles and that of CNTs by transmission electron microscopy (TEM). EXPERIMENTAL DETAILS For the growth of SiNWs, first, a Au thin film of 1.0 nm thick was deposited on a Si{111} surface at room temperature in a vacuum of 10-3 Pa. Next, the Si substrate was loaded into a quartz tube set in a furnace. The substrate was heated to 500 °C for 30 minutes, and then SiH4 gas diluted with Ar (1% SiH4) was flowed into the quartz tube at a flow rate of 1500 sccm for 5 minutes with the pressure of 98 kPa. As a result, numerous SiNWs were synthesized on the substrate. SiNWs were dispersed in ethanol by ultrasonic, and then deposited on a Mo micro grid with a carbon supporting film. For the growth of CNTs, first, a Co thin film was deposited on these SiNWs at room temperature in a vacuum of 10-3 Pa. The average thickness of the Co film ranges from 0.1 to 0.5 nm. Next, the SiNWs on the micro grid were heated to 800 °C in Ar gas at a flow rate of 100 sccm with the pressure of 5 kPa. After the temperature
reached 800 °C, the Ar gas was replaced by ethanol (C2H5OH) gas at a flow rate of 150 sccm and the pressure was kept at 5 kPa. Ethanol gas was supplied for 1
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