Annealing temperature effect on the field emission properties of carbon nanotube films

As the carbon nanotubes (CNTs) films are applied to the field emission cathodes in the vacuum devices, heat treatment in the range of 400°C-500°C is often conducted during the device sealing process, especially for glass-based devices. The annealing temperature effect on the field emission of the CNT films prepared by chemical vapor deposition is investigated. The CNT film annealed at 400°C in air contains less amorphous carbon phase, and shows better field emission properties comparing to the as-grown CNT film. Annealing at 450°C causes serious oxidative damage along the tube walls, resulting in the poor field emission performance. The CNTs annealed at 500°C are all burned out. The experiment shows that the sealing temperature at 400°C or below can be conducted in air, while the sealing temperature above 400°C should be done in N₂ or Ar ambient.