Study on enhancement in emission current of plane-type cathodes based on nanocrystalline silicon

采用脉冲激光烧蚀技术，在纳米硅表面覆盖了一层薄的氧化膜，制备了平面型阴极。电子发射发生在高于Au栅功函数的栅压下，发射效率随栅厚度的减小而增加，对于5 nm Au栅的阴极，发射效率最高可提高4%。在薄的Au薄膜中观察到大量的纳米空穴，这表明发射包括在纳米空穴下排列的纳米晶体直接发射的电子。发射电子的能量分布与栅极电压有很强的依赖关系，在2~4 eV的半高宽范围内，发射电子的能量分布变宽，随着外加电压的增加，发射电子的能级向高能端移动。此外，我们还测量了阴极的发射角。测定值约为4.5°，与常规场发射极相比，平面场发射极具有优势。

Planar-type cathodes based on nanocrystalline Si covered with a thin oxide film fabricated using a pulsed laser ablation technique were demonstrated. The electron emission occurred at the gate voltage higher than the work function of the Au gate, and the emission efficiency increased with decreasing gate thickness and was improved up to 4 % for the cathode with 5nm Au gate. A lot of nanoholes in the thin Au film were observed, suggesting emission included electrons directly emitted from nanocrystalline aligned under nanoholes. The energy distribution of emitted electrons shows strong dependence on the gate voltage that the distributions become broader from 2 to 4 eV in FWHM, and the spectrum moves to the higher energy side with the increase in the applied voltage. In addition, we measured the emission angle of the cathode. The measured value was estimated about 4.5°, showing an advantage of a planer cathode in comparison with a conventional field emitter.