热场致电子发射阴极表面电场瞬态响应特性模拟

Numerical Simulation on Transient Time Response of Thermo-Field Electron Emission Cathode Surface Electric Field

为研究热场致电子发射过程中复杂的非线性空间电荷限制效应和阴极表面电场的瞬态物理过程及特性,基于通用积分形式的热场致电子发射电流密度理论,建立了平板二极管的静电粒子模拟物理模型,以热场致电子发射阴极为边界,模拟获得了热场致发射阴极表面电场的瞬态时间响应曲线。研究结果表明,热场致电子发射过程中,阴极表面电场在皮秒量级时间尺度上呈现为振荡过程,振荡波形特征受二极管间隙距离、阴极材料、逸出功等几何参数和外加电场、温度等运行参数影响;振荡后,二极管阴极表面电场将达到稳定状态,模拟得到的稳态电场与理论分析结果相符;二极管热场致电子发射的外加电场和温度一定时,逸出功越大,阴极表面稳态电场强度越大;二极管阴极材料和外加电场一定时,阴极表面稳态电场强度取决于阴极表面的温度,随温度的升高稳态电场强度呈非线性下降。

In order to investigate the complex and nonlinear space charge effects in thermo-field electron emission process, an electrostatic particle-in-cell simulation model for planar diode has been built based on the universal integral formulas of electron current density theo-ry. In this model, the electron emission boundary condition is set as thermo-field electron emis-sion, and transient time response curves of electric field strength on the thermo-field electron emission cathode surface have been obtained. The simulation results indicate that the electric field on the thermo-field electron emission cathode surface exhibits oscillating characteristic in ps time scale. The oscillating characteristic is affected by geometry parameters, such as gap distance, cathode material, work function, and operating parameters including applied electric field and cathode temperature. The electric field on the cathode surface will oscillate and get to a steady state, while for the steady electric field strength, the simulation results coincide well with the theoretical results. When the applied electric field strength and cath-ode temperature are determined, the larger the work function of cathode material is, the higher the steady electric field strength will be. When the cathode material and applied elec-tric field strength are determined, the steady electric field strength shows a descending in non-linear form with increasing of the cathode temperature.