Nagoya University Synchrotron Radiation Research Center (NUSR), Furo, Chikusa, Nagoya, Aichi, 464-8601, Japan.
School of Engineering/Graduate School of Engineering, Nagoya University, Furo, Chikusa, Nagoya, Aichi, 464-8601, Japan.
Sci Rep. 2023 Feb 10;13(1):2412. doi: 10.1038/s41598-023-29374-6.
Protection of free-electron sources has been technically challenging due to lack of materials that transmit electrons while preventing corrosive gas molecules. Two-dimensional materials uniquely possess both of required properties. Here, we report three orders of magnitude increase in active pressure and factor of two enhancement in the lifetime of high quantum efficiency (QE) bialkali photocathodes (cesium potassium antimonide (CsKSb)) by encapsulating them in graphene and thin nickel (Ni) film. The photoelectrons were extracted through the graphene protection layer in a reflection mode, and we achieved QE of ~ 0.17% at ~ 3.4 eV, 1/e lifetime of 188 h with average current of 8.6 nA under continuous illumination, and no decrease of QE at the pressure of as high as ~ 1 × 10 Pa. In comparison, the QE decreased drastically at 10 Pa for bare, non-protected CsKSb photocathodes and their 1/e lifetime under continuous illumination was ~ 48 h. We attributed the improvements to the gas impermeability and photoelectron transparency of graphene.
由于缺乏既能传输电子又能防止腐蚀性气体分子的材料，自由电子源的保护在技术上具有挑战性。二维材料独特地同时具备这两种所需的特性。在这里，我们报告了通过将其封装在石墨烯和薄镍（Ni）膜中，高量子效率（QE）双碱金属光电阴极（铯钾锑（CsKSb））的有效压力增加了三个数量级，寿命延长了两倍。通过反射模式从石墨烯保护层中提取光电子，我们在连续照明下实现了约 3.4 eV 的 QE 为 0.17%，1/e 寿命为 188 h，平均电流为 8.6 nA，在高达约 1×10 Pa 的压力下，QE 没有下降。相比之下，裸露的、未受保护的 CsKSb 光电阴极在 10 Pa 下的 QE 急剧下降，其连续照明下的 1/e 寿命约为 48 h。我们将这些改进归因于石墨烯的气体不可渗透性和光电子透明性。
