Reduced turn-on voltage of nanocrystalline graphite (NCG) coated silicon field emitter arrays

Ten nanometers of nanocrystalline graphite were deposited on top of fully processed p-silicon tip arrays by a glow discharge method at 900/spl deg/C. Whereas the p-silicon arrays have to be conditioned at 200-250 V prior to reproducible turn-on at about 100-120 V, the NCG coated arrays turn on at 20 V and do not need conditioning. The slopes of Fowler-Nordheim (F-N) plots are smaller by a factor of 5-10 times for the NCG-coated film, suggesting that the field enhancement factor is increased by a factor of 5-10, or the effective work function is decreased. From STM analysis, we find nano-size features at the NCG-Si interface, suggesting the formation of field enhancement sites and not of a reduced work function deposit. Pressure dependency in air and hydrogen, as well as current fluctuations versus current dependencies are similar for the bare and the NCG-coated devices.