Numerical Modeling of a Coaxial-Type Focusing Carbon-Nanotube Emitter Considering Space-Charged Effects

Summary form only given. In the past, prediction of field-emission properties has generally ignored the space-charged effects caused by the emitted electrons near the emitting surface. Normal procedures of predicting the field-emission properties are, first, to solve the Poisson's equation once and for all and, then, move the emitted electrons following the predicted unchanged electric field. However, it has been shown that the resulting emitted current is strongly dominated by the space-charged effect as well as the local fields near the emitting surface. Thus, it is necessary to solve the electrical field self-consistently by taking into account the movement of emitted electrons in the cell. In this paper, field-emission properties of a coaxial-type carbon-nanotube emitter are simulated using a parallel 3D PIC code utilizing unstructured tetrahedral mesh, which is presented in another paper in this meeting. Use of multiple gates not only enhances the local electrical fields near the emitting cathode, but also it helps to focus and control the electron flow onto the anode that is important in designing the field emission display. Computational cells near the emitting surface are refined adaptively according to the improved solution using the parallel adaptive mesh refinement module (PAMR). Results of corresponding I-V characteristics due to effects of geometry of the field emitter, location of the gates, distance between the anode and cathode, magnitude of the applied voltage on the gates are discussed in the presentation