The effects of ion bombardment on the formation of multi-walled carbon nanotubes (MWNTs) are investigated by controlling radio-frequency (rf) glow-discharge plasmas in strong magnetic fields. When a magnetic field is weak (0.03 T), the MWNTs growing directly on an rf electrode are deformed by the bombardment of the high-energy ions generated by a large sheath electric field in front of the rf electrode. On the other hand, when a strong magnetic field (2T) is applied, the MWNTs are observed to be well aligned and not to be deformed even under the condition that the rf electrode is negatively biased. These results can be explained by the fact that the ion bombardment energy is reduced despite the existence of the large sheath electric field, which is caused by the magnetization of the ions in the strong magnetic field.
- Carbon nanotubes
- Ion bombardment energy
- Plasma-enhanced chemical vapor deposition
- Sheath electric field
- Strong magnetic field