Emission Property and Structure of an Ultra Sharp Tungsten Probe

It was previously reported that an ultra sharp emitter can be fabricated during field emissions from a multi-walled carbon nanotube embedded in a conventional electrolytic polished tungsten probe, where the Joule heating of the emission current softens the tungsten tip, and coulomb attraction to the nanotube finery pulled from the tungsten tip resulted in an ultra sharp apex of the tungsten probe, with a curvature of 5 nm radius. In this paper, we report on the emission characteristics and structural analysis of the ultra sharp tungsten probe tip, where the tungsten tip shows a very high emission capacity- exceeding about 1000 muA without any deterioration of the tip apex. The existence of the amorphous tungsten-carbide cap would be the key of the fabrication process and the extremely high current capacity.