Effect of pressure on morphology of the grown layers of carbon nanotubes by modified plasma-enhanced chemical vapor deposition

Synthesis of carbon nanotubes (CNTs) by a modified PECVD method under controlled pressure is reported. This modified tip-plate configuration allows one to investigate the effect of low and subatmospheric pressures on the morphology of the grown layers of nanotubes, which in turn simplifies the fabrication procedure. Using this method we have realized CNIs on silicon substrates at a temperature of 700 degrees C and gas pressures ranging from 10torr to 400torr. Tube diameter varies with the gas pressure and ranges from 25 nm to 250 nm in different samples. The density and preferred growth of CNTs increases essentially with the gas pressure. By controlling the gas pressure, CNTs have been realized in large quantities. Scanning electron microscopy (SEM) has been employed to study the morphology of the grown layers.