Emission from in-situ Ba-coated nanocrystalline graphite/CNT emitters

By depositing thin layers of ~17nm and ~60nm of Ba on nanocrystalline graphite/CNT emitters, it was expected that the current density of the emitters, at a given extraction field, would increase by several orders of magnitudes due to the lowering of the emitter work function. The opposite of what was expected occurred. A drastic decrease in emission current was observed. Since field emission is also governed by the field enhancement factor β, the decrease in β due to the Ba coverage outperformed the decrease in work function such that Φ^3/2/β before Ba deposition was smaller than Φ^3/2(Ba)/β(Ba) after deposition.