Controlled Alignment of Carbon Nanotubes by Hot Filament Chemical Vapor Deposition in a CH4/H2 Plasma
Qiaoqin Yang, Weifeng Chen, Chijing Xiao, and Akira Hirose
Plasma Physics Laboratory, University of Saskatchewan, CA
Keywords: alignment, carbon nanotubes, CVD, plasma
Controlling of the alignment of carbon nanotubes (CNTs) is very important for applications such as scanning probes, sensors, field emitters and nanoelectronics. Controlled growth of CNTs aligned at different angles to the substrate has been achieved by using hot filament chemical vapor deposition (HFCVD) in a CH4/H2 plasma. P-type (100)-oriented mirror polished Si wafer was employed as the substrate. A thin Ni film of thicknesses 50 nm deposited by DC sputtering inside the deposition chamber was used as catalyst. The specimens obtained were characterized by scanning electron microcopy (SEM) and transmission electron microscopy (TEM). When no bias or a positive bias voltage was applied on the substrate, the resultant nanotubes were randomly oriented. When a negative bias voltage was applied, the nanotubes were well aligned and the orientation of the nanotubes was determined by the direction of the electric field lines. The alignment of CNTs can be well controlled by the direction of the electric field lines during the synthesis process. The results indicate that the bombardment of ions has substantial effect on the alignment of CNTs and that the bombardment direction of ions determines the alignment orientation of CNTs.
NSTI Nanotech 2003 Conference Technical Program Abstract