Bulb-shaped field emission lamps using carbon nano-coil cathodes

Bulb-shaped field emission lamps (FELs) using carbon nano-coil (CNC) cathodes were fabricated and their performances were characterized. A straight steel wire grown with CNCs was placed on the symmetry axis in the bulb as the cathode. The anode was defined by a Ni film deposited on the bottom hemisphere of a 60-mm-diameter glass bulb. And a phosphor layer was coated on the Ni film for light generation via cathodoluminescence. A numerical simulation model for this geometry also was constructed. The simulated current-voltage curves agree well with the experimental results and reproduce the trends observed in the experiment. The effects of varying the length and diameter of the cathode were studied. Both experiment and simulation showed that the total field emission current increases with the cathode length and decreases with the cathode diameter. Although the design is simple and inherently low-cost, good uniformity of light emission over the entire anode was demonstrated.