基于有限元参数化设计的碳纳米管的场致增强因子计算

Calculation of CNT’s Electric Field Enhancement Factor Based on Finite Element Method

碳纳米管由于尺寸极小 ,它具有很大的场增强因子 ,且场发射稳定 ,这些特性使碳纳米管成为一种性能优良的场致发射材料。影响碳纳米管发射电流的重要参数是场增强因子 ,这需要求解拉普拉斯方程 ,由于理论解求解很困难 ,有限元方法成为一种有效的工具。使用有限元程序ANSYS对碳纳米管的静态电场进行了计算 ,建立了单根碳纳米管的模型 ,确定了边界条件。研究了金属型碳纳米管尖端周围的电场强度分布 ,为了更好地了解碳纳米管顶端附近的电场对长径比的影响 ,使用了参数化设计语言APDL ,使得分析效率大大提高 ,并且计算结果与实际情况相符。说明这种方法是正确。

Carbon-nanotube (CNT) is well fitted to field emission for its geometry. A very high electric field can be gotten near its apex. Some of advantages, such as low turn of voltage and stable field emission, made CNTs as an ideal field emission material. The field enhancement factor is an important parameter which effects on the emission current obviously. Soluting the Laplace function is needed, however the special geometry made this solution difficult. Finite element method is a good choice with the increase ment of speed and memory of computer. A commercial code ANSYS was used to analyze the field enhancement factor of CNTs. A single CNT model is extracted from the whole array and some suitable boundary conditions are applied to the model. In order to increase the speed of solution, 1/4 part of single CNT model is used in fact. The more accurate results can be got by refining the meshes near apex. The distribution of electric field near the apex of single CNT was analyzed finally. To make the whole process easy and learn better the electric field’s dependence on aspect ratio, an ANSYS parametric design language(APDL), by which great efficient can also be gained, was used. The results are well fitted by the other papers, which testified the whole process: model, mesh and computation. Those methods are good choice to things like this.