Simulation Study Of Carbon Nanotube Field Emission Display With A Self-focus Cathode

The field emission display (FED) attracts more and more concern because it collects both advantage of CRT and flat panel display (FPD). And among a variety of materials for emitter of FED, carbon nanotube (CNT) has already emerged as a potential candidate for the emitter in the FED owing to its excellent field emission characteristics. To solve the problem of degraded pixels in triode CNT-FED, a new self-focus cathode structure was proposed to focus the electron beams and reduce the pixel. Emission of CNT-FED with a concave cathode was simulated using ANSYS software.We studied the difference of electron beam focusing between concave cathode model and that with flat cathode, and found that the electron beam emitted from the flat cathode diverges more than that emitted from the concave cathode obviously. As the curvature of concave increases gradually, the focusing effect is enhanced and the radius of electron beam on the anode decreases. Further increase of the curvature leads to, however, intersecting of the electron beams and augment of the beam radius. The intersect electron beams are similar to the beam through a lens, but the electron beams do not intersect at one point, but throughout a narrow range. It is expected to partly equalize the error generated from the manufacture of CNT emitter layer.We discussed the influence of important parameters on the emission characters of emission unit. As Vg is enhanced gradually, the electron beam moves towards the +X axis , the beam radius first reduces slightly and then increases, and the higher Vg generates higher local electric field. As the thickness of dielectric layer (Dgc) or the diameter of gate aperture (d) increases, the beam radius also reduces and then increases, but the electron beam moves towards the -X axis and the electric field on the emitter surface reduces slowly. To avoid the screen effect, we optimized the space between the emission units.With optimal configuration of CNT-FED, the electron beams can be focused onto a very small anode area. For the strengthened current density on anode in this area, the brightness is intensified. Self-focus cathode electrode may be applicable to the design of CNT-FED with high resolution and low power consumption.