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Carbon nanotubes (CNTs) have attracted great attention as electron emitters. These field emission cathodes operate at room temperature without a heater, in contrast to thermionic emitters that often require considerable heater power for proper operation. Furthermore, CNTs have the advantage of large aspect ratios, allowing large local electric field enhancements at the nanotube tips, further increasing their attractiveness as field emitters. However, due primarily to materials issues such as limited emission site density, screening effects, and weak interfacial bonding, no large area cathodes have been operated at high current to date. In this paper, we report on the design, fabrication, and testing of a large-area CNT cathode operating at high-voltage (>200 kV) and high-current density (30 A/cm2). The cathode lifetime exceeded four thousand pulses. The current density and voltage achieved represent a significant achievement and indicate that such a cathode design can prove valuable as a high-current, large-area emitter.
Date of Publication: Oct. 2004