Vertically aligned carbon nanotubes (CNTs) were synthesized using FeNi or Fe sputtered catalyst layers on glass substrates by radio frequency or direct current plasma enhanced chemical vapor deposition (rf- or dc-PECVD). This article compared the growth mechanisms of CNTs synthesized by rf- and dc-PECVD, based on gas flow rate, plasma power, and catalysts. Tip growth CNTs were produced at 180 °C, 10 SCCM (SCCM denotes cubic centimeter per minute at STP) CH4, and 30 W by rf-PECVD using 8 or 4 nm FeNi or 4 nm Fe island films sputtered onto glass substrates. CNTs could not grow using dc-PECVD under the same deposition conditions; tip growth of CNTs occurred at 180 °C, 15 SCCM CH4, and 50 W using dc-PECVD with sputtered FeNi island catalysts on increasing the plasma power and CH4 flow rate. This article explained why rf-PECVD provided more efficient decomposition of gas molecules than dc-PECVD by plasma theory. The major difference between rf- and dc-PECVD was the higher concentration of reactive radicals in the former. However, in dc-PECVD, the CNT growth was well aligned vertically. FeNi thin film catalysts exhibited higher activity and better wetting ability than the Fe island thin film catalysts.