The monochromatic photoemission from diamondoid monolayers provides a new strategy to create electron sources with low energy dispersion and enables compact electron guns with high brightness and low beam emittance for aberration-free imaging, lithography, and accelerators. However, these potential applications are hindered by degradation of diamondoid monolayers under photon irradiation and electron bombardment. Here, we report a graphene-protected diamondoid monolayer photocathode with 4-fold enhancement of stability compared to the bare diamondoid counterpart. The single-layer graphene overcoating preserves the monochromaticity of the photoelectrons, showing 12.5 meV ful width at half-maximum distribution of kinetic energy. Importantly, the graphene coating effectively suppresses desorption of the diamondoid monolayer, enhancing its thermal stability by at least 100 K. Furthermore, by comparing the decay rate at different photon energies, we identify electron bombardment as the principle decay pathway for diamondoids under graphene protection. This provides a generic approach for stabilizing volatile species on photocathode surfaces, which could greatly improve performance of electron emitters.

中文翻译：

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石墨烯稳定的类金刚石的单色光电阴极

菱形单分子层的单色光发射提供了一种新的策略来创建具有低能量色散的电子源，并使紧凑型电子枪具有高亮度和低电子束发射率，从而可以实现无像差成像，光刻和加速器。但是，这些潜在的应用受到光子辐照和电子轰击下类金刚石单分子层降解的阻碍。在这里，我们报告了石墨烯保护的类金刚石单层光电阴极，与裸类类金刚石相比，其稳定性提高了4倍。单层石墨烯外涂层保留了光电子的单色性，在动能的一半最大分布处显示了12.5 meV的有效宽度。重要的是，石墨烯涂层可有效抑制类金刚石单层的解吸，通过至少100 K增强其热稳定性。此外，通过比较不同光子能量下的衰变速率，我们确定电子轰击是石墨烯保护下类金刚石的主要衰变途径。这为稳定光电阴极表面上的挥发性物质提供了一种通用方法，这可以大大提高电子发射器的性能。