Bialkali photocathodes, such as cesium potassium antimonide (CsK2Sb), can generate a high-brightness electron beam using a high-power green laser. These photocathode materials have potential applications in advanced accelerators and electron microscopes. It is known that the quantum efficiency (QE) of these photocathodes is affected severely by their substrates; however, reusability of the substrates is not well known. Here, we use graphene, silicon (Si), and molybdenum (Mo) substrates to evaluate the effects of substrates on the QE of redeposited CsK2Sb photocathodes after thermal cleanings. We found that the QE of CsK2Sb photocathodes redeposited on a graphene substrate after thermal cleaning at 500 °C remained largely unchanged. On the other hand, the QE of redeposited photocathodes on Si and Mo substrates after thermal cleaning at the same temperature decreased drastically. We used x-ray photoelectron spectroscopy to quantitatively evaluate the residues of photocathodes after thermal cleaning at 400 °C and 500 °C. We found that Sb, K, and Cs are removed by thermal cleaning at 500 °C for the graphene substrate, but all or the majority of these elements remained on the Si and Mo substrates. The results were consistent with our density functional theory calculations for the case of Si, which we investigated. Furthermore, our angle-resolved photoemission spectroscopy on graphene indicated that its intrinsic electronic structure is preserved after photocathode deposition and thermal cleaning at 500 °C. Hence, we attributed the difference in the amount of photocathode residue to the unique dangling-bond-free surface of inert graphene. Our results provide a foundation for graphene-based reusable substrates for high-QE semiconductor photocathodes.

中文翻译：

---

石墨烯作为双碱光电阴极的可重复使用基材

双碱光电阴极，例如锑化铯钾 (CsK2Sb)，可以使用高功率绿色激光产生高亮度电子束。这些光电阴极材料在先进的加速器和电子显微镜中具有潜在的应用。众所周知，这些光电阴极的量子效率 (QE) 受到其基板的严重影响；然而，基材的可重复使用性并不为人所知。在这里，我们使用石墨烯、硅 (Si) 和钼 (Mo) 衬底来评估衬底对热清洁后再沉积 CsK2Sb 光电阴极 QE 的影响。我们发现，在 500 °C 下热清洗后，再沉积在石墨烯衬底上的 CsK2Sb 光电阴极的 QE 基本保持不变。另一方面，在相同温度下热清洗后，再沉积在 Si 和 Mo 衬底上的光电阴极的 QE 急剧下降。我们使用 X 射线光电子能谱定量评估了在 400 °C 和 500 °C 下热清洗后光电阴极的残留物。我们发现 Sb、K 和 Cs 通过在 500 °C 下对石墨烯基板进行热清洗而被去除，但这些元素的全部或大部分仍留在 Si 和 Mo 基板上。结果与我们研究的 Si 情况的密度泛函理论计算一致。此外，我们对石墨烯的角分辨光电子能谱表明，在 500 °C 的光电阴极沉积和热清洁后，其固有的电子结构得以保留。因此，我们将光电阴极残留量的差异归因于惰性石墨烯独特的无悬空键表面。我们的结果为用于高 QE 半导体光电阴极的基于石墨烯的可重复使用基板提供了基础。