Origin of low threshold field emission from nitrogen-incorporated nanocrystalline diamond films

Highly conductive, nitrogen-incorporated nanocrystalline diamond films with quasimetallic character emit electrons at low turn-on fields (∼3 V μ m^-1). These films exhibit stronger delocalization of carriers, indicative of smaller energy separation between the defect bands in the band gap. We show that the emission level derived from the measured emission characteristic and electron affinity shifts upward (up to a few eV) with increasing the film conductivity, thereby decreasing the effective potential barrier height for the emission. This is attributed to higher probabilities of electron injection into upper defect levels during the transport process, originating from internal band bending and increasing band continuity.