Enhancement of field emission of aligned carbon nanotubes by thermal oxidation

To improve the field emission current density of aligned carbon nanotubes grown by thermal chemical vapor deposition, postgrowth thermal annealing was conducted at 850°C for 1h in vacuum plus at 465°C for 2h in air. It was found that the highest field emission current density significantly improved by a factor of 4 (from 19to79mA∕cm2), which is due to the substantial increase of the emitting area of the carbon nanotubes after annealing. This result is important for applications of using carbon nanotubes as high current electron sources, microwave devices, flat panel displays, etc.