Fig. 4: Characterizations of the operation performances of the proposed cathode.

a The emission currents and transmittance as functions of the turn-on time of the cathode. The insert is the measurement schematic of the triode structure, the currents of anode and gate can be measured using the electrometer (A_a and A_g) under applied emitter voltage (V_c). The blue, green, and black dots correspond to the measured electron beam (E-beam) transmittance, cathode current, and anode current data, respectively. Meanwhile, the yellow dashed line represents the fitted E-beam transmittance. b Current-electric field (I-E) curves of the cathode with SiN_x-gate, the inset is a comparison of E-beam transmittances between cathodes based on SiN_x-gate and Au-gate. The green, black and purple dots correspond to the measured cathode current, anode current and gate current, respectively. Meanwhile, the red and black five-pointed stars in the inset represent the measured E-beam transmittances based on SiN_x-gate and Au-gate, respectively. c The 100 h current stability of the cathode upon ~100 μA, the inset is an enlargement of the E-beam transmittance over a 20 s interval. The emitter area is 0.057 cm². The purple, green and black dots correspond to the measured E-beam transmittance, cathode current and anode current, respectively. Source data are provided as a Source Data file.