Analysis of plasma for carbon nanotube growth by plasma-enhanced chemical vapor deposition
- PDF / 244,049 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 32 Downloads / 256 Views
0901-Rb24-03.1
Analysis of plasma for carbon nanotube growth by plasma-enhanced chemical vapor deposition A. Ozeki, Y. Suda, A. Okita, J. Nakamura1, A. Oda2, Y. Sakai and H. Sugawara Graduate School of Information Science and Technology, Hokkaido University North 14, West 9, Sapporo 060-0814, Japan 1 Institute of Materials Science, University of Tsukuba Tsukuba, Ibaraki 305-8573, Japan 2 Graduate School of Engineering, Nagoya Institute of Technology Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan ABSTRACT Optical emission spectra of a CH4/H2/Ar gas mixture plasma were observed during carbon nanotube (CNT) growth in RF plasma-enhanced chemical vapor deposition. CNTs with diameters of ~10−30 nm and length of ~6 µm were grown on double- and triple-layered films of catalyst/support materials (FexOy/TiO2 and Al2O3/FexOy/Al2O3) at the total gas pressures of 1−10 Torr with gas flow rates of CH4 = 27 sccm, H2 = 3 sccm, and Ar = 1 sccm. The number density of CNTs increased with the gas pressure, and Al2O3/FexOy/Al2O3 (each thickness of 1 nm) film yielded the thinnest CNTs with a high number density among the present catalysts. The spatial distributions of H atom relative density in the plasma were obtained by actinometry. The H relative density decreased with the pressure, and this suggests the suppression of CH3 radical generation in the plasma.
INTRODUCTION Since carbon nanotubes (CNTs) were discovered by Iijima of NEC [1], they have extensively attracted us because of their excellent structural and physical properties, such as high aspect ratio, tensile strength, thermostability, chemical stability, specific thermal and electrical conductivities, field emission property [2]. It is well known that single-walled carbon nanotubes (SWNTs) can be metallic or semiconducting depending on its chirality. Research on CNTs for the application to field effect transistor, nanometer-sized wiring in LSI, in-depth probe of scanning probe microscopy, and field emission device in flat panel displays has been performed [2−4]. In order to achieve these applications, the establishment of CNT synthesis technique with large quantity and high controllability is necessary [5]. We have studied plasma-enhanced chemical vapor deposition (PECVD) of CNTs and the correlation between CNT growth and plasma [6]. In PECVD, plasma dissociates carbon source gases, and generates ions and radicals. Supply of the radicals can lower the CNT growth temperature than that of thermal CVD [7]. PECVD is also able to grow vertically aligned CNTs
0901-Rb24-03.2
on substrates because of the strong electric field, which is generated in plasma sheath region. On the other hand, PECVD has a demerit to deposit unnecessary amorphous carbons and to make the growth mechanism of CNTs complicated because of the generation of various species in plasma (CxHy radicals, ions, and neutral species). For better control of CNT growth in PECVD, it is essential to analyze the plasma and to understand the correlation between the plasma and CNTs grown. There are several techniques to diagno
Data Loading...
