The Simulation Of Surface-conduction Electrons Emission Cathode

As the most familiar interface for the communication between men and machine,the application of display devices has been deep into all aspects of socialdevelopment.With the development of information society and the improvement ofpeople’s aesthetic standards, display devices show a trend of high-definition, flat anddigital. The champion in twentieth Century display field－CRT devices have beengradually withdraw from the market because of their large volume and big quality,and the flat display devices with liquid crystal display as the representative arebooming. Among them, the field emission displays as the flat display devices of CRTsucceed to the CRT display quality and basic technology, therefore, over the yearsthey have been the research hot spot in flat panel display technology field.Because the light-emitting principle of field emission displays is similar to theCRT devices and the flat structure is similar to that of the LCD, PDP, so the coretechnology is the field emission cathode, including the cathode structure and emissionmaterial. In this paper, the self-focusing model proposed by our lab is improved andthe distribution of electric field is simulated, then the influence of the model structureand the emission material on the electric field and the electrons trajectories isdiscussed.Using the finite element method, the electrons trajectories near the cathode issimulated and that the electrons near the cathode can not reach the anode is found.The simulation results show that: the electric field produced by the grid with thecathode will shield that produced by the anode with the cathode, so the electrons nearthe cathode can not reach the anode. The simulation of the electrons trajectories showthat the structure of the cathode has a big influence on the trajectories.A perfect model with the the cathode height of0.5μm, the anode voltage of400V,and radius of the arched edge of20μm (in other words, the radian is0.056π) isconcluded, and in this model the electron emitting from the material will reach theanode as long as the distance between its starting point and the cathode is larger than0.2μm.At the same time, the influence of the material on the electric field is discussed.The material of larger relative permittivity will help increase the electrons emissionefficiency in the models of rectangular electrodes. And the trajectories of electronsnear the grid also show that Decreasing the cathode height, increasing the anodevoltage and applying the arched electrodes with big radium will improve the electronemission efficiency greatly.