Numerical analysis of pressure dependence on carbon nanotube growth in CH4/H2 plasmas
- 作者：Akinori Oda ; Yoshiyuki Suda ; Atsushi Okita
- 关键词：Carbon nanotube ; Plasma-enhanced chemical vapor deposition (PECVD) ; Plasma modeling ; Methane ; Radical neutrals ; Non-radical neutrals
- 刊名：Thin Solid Films
- 出版年：2008
- 期刊代码：78_00406090
- 类别：ph
- 出版时间：1 August 2008
- 卷：516
- 期：19
- 页码：6570-6574
- 文件大小：372 K
摘要
The pressure dependence of a CH4/H2 gas mixture plasma was analyzed for carbon nanotube (CNT) growth by one-dimensional fluid modeling and compared with the experimental results obtained under the same condition as the analysis. When the gas pressure was 10 Torr, vertically aligned CNTs are grown with a high number density. As the pressure increases, densities of the non-radical neutrals, radical neutrals and ions with a lager molecular weight than CH4 tend to increase but those of the smaller species including CH3 and CH2 decrease. This is explained by the hydrogen abstraction reaction of CH4 with H atoms and the production reaction of C2H5 due to incorporation of CH3 radicals. The fluxes of these carbon-bearing species onto the substrate surface were evaluated. As the gas pressure increased, the flux of positive ions decreased. Instead, the contribution of higher-order non-radical species, including C3H8, to CNT formation at high gas pressure is suggested.