The generation of a field emission (FE) cathode electron source has attracted wide attention for its miniaturization, high-frequency operability, and low energy consumption. However, the FE performance of cold cathodes is limited by poor current stabilities of carbon nanotube (CNT) emitters. Coating CNTs with sp³-bonded carbon coatings is considered as a successful approach to stabilize the FE currents. High-quality ultrathin diamond-like carbon (DLC) films, which serve as sp³ carbon coatings, are deposited uniformly on CNTs by filtered cathodic vacuum arc evaporation in this research. The thicknesses of DLC coatings and the field enhancement factors of pristine CNTs affect to a large extent the FE properties. An optimum coating thickness of DLC layers corresponding to the lowest threshold field exists due to space-charge-induced band bending, at which the depletion region of the DLC layer in equilibrium is maximized. The optimum coating thickness increases with the geometric field enhancement factor of pristine CNTs bundles, the relationship of which illustrates an obvious difference between planar cold cathodes and nanostructured field emitters, and could be extended to optimize double-layer or multi-layered nanostructures serving as FE emitters with high reliability.

中文翻译：

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碳纳米管上超薄类金刚石碳涂层的最佳厚度对几何场增强因子的依赖

场发射（FE）阴极电子源的产生以其小型化，高频可操作性和低能耗而受到广泛关注。但是，冷阴极的有限元性能受到碳纳米管（CNT）发射极电流稳定性差的限制。用sp ³键合碳涂层涂覆CNT被认为是稳定FE电流的成功方法。高质量的超薄类金刚石碳（DLC）膜，可作为sp ³在这项研究中，通过过滤的阴极真空电弧蒸发将碳涂层均匀地沉积在CNT上。DLC涂层的厚度和原始CNT的场增强因子在很大程度上影响FE特性。由于空间电荷引起的能带弯曲，存在与最低阈值场相对应的DLC层的最佳涂层厚度，在该处，平衡状态下DLC层的耗尽区最大。最佳涂层厚度随原始CNTs束的几何场增强因子而增加，其关系说明平面冷阴极与纳米结构场发射体之间存在明显差异，并且可以扩展以优化用作FE的双层或多层纳米结构发射器具有很高的可靠性。