Field emission from mechanical pencil lead and related materials

It is known that carbon-related materials are suitable for field emission sources owing to its chemical and physical high stability and that some of them show superior field emission features; a very low threshold applied field and a high current density. In the case of emitter sources with an atomically sharp tip with a high aspect ratio such as carbon nanotubes, we have usually tried to explain the low threshold field by geometrical field enhancement. It has been reported, however, that even field emitters with no nano-protrusions sometimes give extremely low threshold applied fields [1, 2]. And it is noted that the FE features from carbon nanotubes have not been quantitatively confirmed to reproduce in the framework of Fowler-Nordheim (F-N) criterion because it is not possible to estimate the local electric field at the emission sites within classical electromagnetism in the case of atomically sharp tips.