Abstract
The electron field emission (EFE) properties of nanocrystalline diamond (NCD) films were markedly enhanced when prepared with a plasma post-treatment on the ultra-small-grain granular-structured diamond films, as compared with conventional NCD films directly grown on Si using CH 4 /Ar/H 2 plasma. Transmission electron microscopy reveals that the primary influence for the improvement of the EFE properties of these films was owing to an induction of the nanographitic phase in the films, while the ultrasmall diamond grains (∼5 nm) coalesced to form large diamond grains (∼hundreds of nanometers) during the plasma post-treatment process. This modification of the granular structure of the NCD films was greatly enhanced when a negative bias voltage (-300 V) was applied during the plasma post-treatment process. Moreover, three-electrode microplasma devices performed overwhelmingly better than twoâ€electrode devices, exhibiting a higher plasma current density with a longer lifetime stability. These microplasma devices emit ultraviolet emissions efficiently. Such conductive NCD films offer an improvement as cathode materials for microplasma devices compared with the conventional electrode materials such as Mo metal.