Field emission enhancement of carbon nitride films by annealing with different durations

Magnetron sputtered carbon nitride films (CNx) were annealed at 750 °C for periods from 30 to 120 min. Effects of annealing with different durations on the field emission of CNx films were investigated and related to the variations of chemical bonding and surface morphology induced by annealing. The results show that annealing effectively enhances field emission ability of the CNx films and that the threshold field was lowered from 13 to 5 V/(mu)m. The measurements of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) indicated that annealing leads to a loss of N content and to formation of more graphite-like sp^2 C clusters in the films, and simultaneously the film surface becomes rougher after annealing, all of which is attributed to the increased film field emission. A large number of sp^2 C clusters with good conductivity enables tunneling in the film, making electron emission easier, and moreover, a rougher surface also improves the field enhancement factor of the films. However, continuing to increase annealing time eventually lowers the field emission of the films.