纳米碳管阵列场增强因子的计算

采用悬浮球模型，结合对称的镜像电荷层方法，对静电场中纳米碳管阵列的场增强因子进行了计算，并在考虑极板间距的情况下，对其计算结果做了修正.结果表明：纳米碳管阵列的间距对纳米碳管阵列的场发射性能影响很大.当纳米碳管阵列中碳管间距小于碳管高度时，场增强因子随间距的减小而急剧减小；而当碳管间距显著大于碳管高度时，场增强因子几乎不变.但当考虑阴阳极之间单位面积通过的场发射电流时，可论证当管间距与管高度相若时，能使场发射电流密度最佳(最大).另外，极板间距对场增强因子的影响很小，但是可以通过减小极板间距，来降低纳米碳管作为场发射体的场发射的开启电压，优化纳米碳管的场发射性能.关键词：纳米碳管阵列场增强因子开启电压

Calculation of field enhancement factor of the carbon nanotube array

To estimate the apex field enhancement factor associated with an array of carbon nanotubes (CNTs) on a planar cathode surface, the model of floating spheres between parallel anode and cathode plates is proposed. An approximate formula for the enhancement factor is derived, showing that the intertube distance of a CNT array critically affects the field emission. When the intertube distance is less than the height of the tube, the enhancement factor decreases rapidly with decreasing distance, qualitatively in agreement with the numerical simulation. Considering the field emission current density, the field emission can be optimized when the intertube distance is comparable with the tube height, in accordance with the results from experiments. Finally, the influence of the anode-cathode distance on the enhancement factor is also discussed, showing that the anode-cathode distance has little effect on the field emission from CNT array. Thus, we can reduce the threshold voltage to some extent by decreasing the anode-cathode distance.