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The effect of an electron extraction electrode on electron emission for a high-performance electron beam was studied using vertically aligned carbon nanotube emitters as a cold cathode. For the lower electron emission regime (anode current less than 1 mA), the gate electrode structure and materials used had little effect on the electron emission current. However, at the higher electron emission regime (anode current higher than 1 mA), the gate electrode materials and structure do begin to deviate from an ideal Fowler–Nordheim plot by the thermal and electrostatic load on the gate electrode, especially for the small cathode area. The gate mesh bends upward under a higher current load, which then increases the gate leakage current. The upward bending in the gate mesh electrode could reduce the effective electric field by increasing the gate to cathode distance, resulting in saturation of the electron emission current. For higher electron emission currents on the anode, a gate electrode comprising a lower thermal expansion coefficient material is suitable for small cathode area electron beams. [ABSTRACT FROM AUTHOR]

The authors fabricated an optimized electron beam(e-beam) with a carbon nanotube(CNT)cathode and triode configuration. CNT emitters grown with a resist-assisted patterning process were used as an electron source. The gate mesh was aligned with the CNT emitter islands for a lower leakage current, resulting in a higher electron emissioncurrent and transmission ratio. Additionally, the width between CNT islands and the pitch between CNTs were optimized to enhance the electric field at the tip of the CNT emitters. With the optimized e-beam module, consisting of a CNTcathode and gate mesh, CNT pitch of 30 µm, dot size of 3 µm, line width of 210 µm, and gate mesh width of 75 µm, the emission current showed an increase of 165 times and operated for more than 500 h with DC driving. The optimized e-beam can be a building block for vacuum nanoelectronic devices. [ABSTRACT FROM AUTHOR]