The significance of plasma heating in carbon nanotube and nanofiber growth

The effect of the plasma on heating the growth substrate in plasma enhanced chemical vapor deposition (PECVD) of carbon nanotubes is characterized for the first time. This effect, which is commonly ignored in the nanotube/nanofiber literature, is the sole heating mechanism in this work for catalyst pretreatment and growth of straight and vertically aligned multiwalled carbon nanofibers. Significant temperatures, as high as 700°C, are induced from a C ₂H₂:NH₃ direct current (dc) plasma with no other heat source present. To model the behavior of the plasma-heated substrate platform, we have developed a 1-D dc discharge model that incorporates a cathode platform energy balance, including ion bombardment, thermal radiation, and solid and gas conduction. The predicted gas-phase species present are correlated with the morphology of nanofibers grown by exclusive plasma heating as well as by heating from plasma in combination with a conventional resistive heater. The understanding of plasma heating and its accurate modeling are essential for reactor design for wafer scale production of vertically aligned nanofibers.