The synthesis of vertically aligned single-walled carbon nanotubes (VA-SWNTs) by plasma-enhanced chemical vapor deposition (PECVD) was achieved at 500-600 °C, using ethylene as the carbon source and 1 nm Fe film as the catalyst. For growth of high-quality VA-SWNTs in a plasma sheath, it is crucial to alleviate the undesirable ion bombardment etching effects by the optimization of plasma input power and gas pressure. The resistibility of synthesized VA-SWNTs against ion bombardment etching was found to be closely related to the growth temperature. At relatively low temperature (500 °C), the VA-SWNTs were very susceptible to ion bombardments, which could induce structural defects, and even resulted in a structural transition to few-walled nanotubes. For capacitively coupled radio frequency (rf) PECVD operating at moderate gas pressure (0.3-10 Torr), the ion bombardment etching effect is mainly dependent on the ion flux, which is related to the plasma input power and gas pressure.