The Influence Of Space Charge Effect On Thermal-field Electron Emission

This paper is mainly composed of two parts.Firstly,the space charge effect during a thermal-field electron emission on a metal tip is researched.Secondly,the space charge effect of a trap-filled dielectric solid is researched.For the first aspect,the hyperboloid metal tip as a cathode under high voltage where the micron gap between anode and cathode is vacuum is studied.The heat effect such as Nottingham effect is considered,which may cause temperature high on the tip.Therefore,a general thermal-field emission equation is adopted to calculate the current density on the tip and study the efffect of temperature on electron emission.A selfconsistent method is proposed innovatively to accurately consider the space charge effect for a thermal-field emission.The conclusion is found that the space charge density,potential distribution,surface electric field and current density are greatly influenced by space charge effect.Then,the effect of non-uniform work function and initial launch velocity on the properties of electron emission,such as the emittance of electron beam and the current density on the surface.Finally,the Nottingham effect on the tip is studied.And the non-uniform heat on the tip is studied.In the research above,the model for electron emission on a tip is provided and the impact of space charge effect on the electron emission is researched.For the second aspect,the space charge effect in a plane anode and cathode is studied.The nano gap between anode and cathode contain two different mediums,including vacuum and trap-filled dielectric solid,or two different trap-filled dielectric solid.The space charge effect current can't be simply obtained by equation.We innovatively propose a method to get the relationship between current and vlotage without solving Poisson equation.And the effect electron mobility and effect resistivity are introduced to rapid calculation of the current density in the solid.The phenomenon in the research is found that the current density limit for space charge can be divided into three regime as trap charge limit regime,space charge limit regime and Ohm limit regime.Then,the effect of proportion of two mediums,electron mobility and limit regime on the scaling of current density and voltage is studied.In summary,the space charge effect of metal tip and trap-filled multi-layer electrode is researched.