【摘要】 为研究二极管热场致发射过程中阴极表面热效应的发展过程及相关影响因素,在阴极表面建立了微米级圆台形微凸起物理模型,用数值方法对阴极表面的焦耳加热、热传导、诺廷汉效应等热电物理现象进行了研究,对比了不同形状微凸起、不同外加电场及诺廷汉效应对微凸起中温度分布及温度随时间变化规律的影响。结果表明:微凸起的形状,尤其是顶底半径比会显著影响微凸起中的温度分布规律;在只考虑焦耳加热及热传导效应时,微凸起中的最高温度总是出现在其顶端,但将诺廷汉效应也考虑后,最高温度点将会偏离微凸起顶端而朝微凸起内部移动,外加电场越弱,微凸起中温度最高点出现的位置越靠近微凸起内部;诺廷汉效应会使微凸起中最高温度达到阴极材料熔点所需的时间提前。更多还原

【Abstract】 To investigate the nonlinear process of thermal effects on cathode surface in thermal field emission,a model of truncated cone microprotrusion(MP)in scale of micron is built,and thermal electric phenomena,such as Joule heating,heat conduction,and Nottingham effect(NE)are numerically studied.Temperature profiles and time evolution of temperature in MP of different shapes with and without NE under various applied electric field strengths are obtained.The results demonstrate that the shape of MP,especially the ratio of top radius to bottom radius of the MP,can significantly affect the temperature distribution in the MP.If Joule heating and heat conduction are included in the model,the maximum temperature will always occur on the top surface of the MP.However,the position at which the maximum temperature occurs will move away from the top surface if NE is also taken into account in the calculation model.The maximum temperature,which is the melting point of the cathode material,will occur nearer to the inside of MP as the applied electric field strength decreases.The NE will accerlerate the process for the maximum temperature to reach the melting point of the cathode material.更多还原