Synthesis of ultra long vertically aligned carbon nanotubes using the rapid heating and cooling system in the thermal chemical vapor deposition process

Vertically aligned carbon nanotubes (CNTs) were synthesized on a lithographically patterned silicon/silica substrate coated with an ultra thin iron film. The process was performed using different thickness of iron700–900 °C using a rapid heating and cooling system (RHCS) in a thermal chemical vapor deposition (CVD) chamber. The substrate was placed on the heater, which can be heated from room temperature to 900 °C within 20 s, and cooled from 900 °C to 250 °C within 25 s. Acetylene was used as the carbon precursor and the mixture of hydrogen and argon was adopted as carrier gas. An ultra high growth rate up to 50 μm/min was detected and a vertically aligned thick CNT array near 500 μm was attained under a low reaction pressure of 10 Torr. The control of CNT layer thickness on the silicon and the silica-patterned substrates was studied. Furthermore, the effects of iron layer thickness on the growth rate and the diameter of the vertically aligned CNTs were also investigated.