Fabrication and beam characteristics of an ultra-sharp electrode for field emission electron beam

In this paper, an ultra-sharp tungsten needle electrode for field emission electron beam using the electro-chemical etching method is fabricated and the current-voltage (I-V) characteristics, emission stability, angular and energy distribution of beam are evaluated. In our setup, NaOH and KOH are used as electrolyte solution in order to fabricate the needle electrode. Throughout the experiments, we observes that the taper length of needle electrode varies from 150 μm to 250 μm according to the applied voltage and the concentration. The electron beam stability is measured to be within 5% for total emission current during 4 hours operation. Meanwhile, the ignition voltage is measured to be low at ∼300V. The radius of curvature for needle electrode is experimentally found to be 220Å using a linear fitting of Fowler-Nordheim plot, which is in remarkably good agreement with that of image size obtained from a scanning ion microscope.