Synthesis of carbon tubes using microwave plasma-assisted chemical vapor deposition

Carbon tubes were successfully produced using microwave plasma-enhanced che mical vapor deposition on silicon, quartz, and ceramic substrates. The carb on tubes, about 80-100 nm in diameter and a few tens of microns in length, were formed under methane and hydrogen plasma at 720 degrees C with the aid of iron oxide particles. In this approach, an average tube density of abou t 10(9) cm(-2) was obtained. The crooked and nonuniform diameters of some t ubes suggested that they were composed of incompletely crystallized graphit ic shells due to existing defects. The characteristic of the tubes grown up ward on the silicon substrate accounted for a remarkably large electron fie ld emission current of 0.1 mA/cm(2) from the surface of the tube sample at a low turn-on field of 3 V/mu m.