Carbon based thin film cathodes for field emission displays

Thin films of nitrogen doped and undoped amorphous carbon were investigated for their application as field emission cathode materials. Field emitter films based on amorphous carbon were deposited by sputtering of graphite employing an electron cyclotron resonance plasma as argon ion source. The a-C films with a nitrogen content of 0.6 at. per cent showed the best vacuum electronic properties. Field emission of electrons started at macroscopic electrical fields as low as 3.2 V mu m (current density 1 x 10(exp -5) mA/mm2) and current densities up to 0.6 mA/mm2 were achieved at an electrical field of 5.8. V/mu m. To locate the emission sites the excitation of a low voltage phosphor (ZnO:Zn) was monitored by a CCD camera. The film resistivity of the a-C films is in the range of 0.1-1 Ohm cm. As revealed by nanoindentation measurements the microhardness is 10-15 GPa indicating a relatively low sp(3) content compared to tetrahedral amorphous carbon (ta-C) films.