Field penetration and its contribution to field enhanced thermionic electron emission from nanocrystalline diamond films

Field emission from sulfur doped nanocrystalline diamond films is characterized by intense emission sites with nm scale diameters. Field emission measurements were obtained at room temperature and analyzed in terms of the Fowler–Nordheim expression where electron emission is due to tunneling through a diminished barrier. The electron emission versus temperature was also recorded at a series of applied fields from 0.5 to 0.8 V/μm. These results were analyzed in terms of a modified Richardson–Dushman relation which describes field dependent thermionic emission. It was found that both sets of data could be fit with a work function of 2.0 eV and a field enhancement factor of  1750. The large field enhancement could not be correlated with specific structures on the relatively flat surfaces. The field and thermionic-field emission from the sulfur doped nanocrystalline diamond films is evaluated by a model which includes barrier lowering as a result of field penetration effects.