Locally resolved field emission area and its effect on resulting j-E characteristics: Case study for planar thin film ultrananocrystalline diamond field emitters

In this work we present the results of numerical processing of extensive datasets of electron field emission (FE) micrographs obtained from planar nitrogen-incorporated ultra-nanocrystalline diamond ((N)UNCD) films deposited on different substrates. The micrographs were acquired concurrently with the FE measurements performed in a parallel-plate configuration. The extracted electrons were collected by a phosphor imaging anode screen, which converted an electron emission pattern into a light emission pattern representing electron emission site distribution on the surface of (N)UNCD. We establish a quantitative correlation between the effective emission area and the applied electric field S(E). Moreover, we find that, when the measured current is normalized by S(E), all current density curves demonstrate a strong kink and saturate at about 100 mA/cm
²
independently of the substrate, whereas normafization by the total area of a cathode does not lead to such behavior.