A clustered carbon nanotube (CNT) cold cathode was investigated for low-energy electron sources. The design addresses nonuniform emission within large clusters and electrostatic screening between adjacent clusters. COMSOL simulations were used to compare cluster diameter and spacing. A cluster diameter of 1 mm provided an effective-emission proportion close to 100% at a normalized-field threshold of 0.5. A spacing ratio (D−2R)/H = 4 substantially weakened screening while maintaining emitter density. The optimized cathode was fabricated on a copper substrate by chemical vapor deposition. Diode tests with a nominal gap of 700 μm gave a turn-on field of 0.66 V/μm and a maximum measured current of 201.33 μA at 1000 V. During a 15 min test at 500 V, the current decreased from 2.377 to 2.182 μA, corresponding to an 8.2% decay. These results support the cathode design for subsequent low-energy electron-gun integration.
 

carbon nanotube; field emission; low-energy electron source; screening effect; chemical vapor deposition