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 (CsK 2 Sb)) 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 –3 Pa. In comparison, the QE decreased drastically at 10 –6 Pa for bare, non-protected CsK 2 Sb 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.
Guo, Lei, Liu, Fangze, Koyama, Kazuki, Regis, Nolan, Alexander, Anna M., Wang, Gaoxue, DeFazio, Jeffrey, Valdez, James A., Poudel, Anju, Yamamoto, Masahiro, Moody, Nathan A., Takashima, Yoshifumi, & Yamaguchi, Hisato (2023). Rugged bialkali photocathodes encapsulated with graphene and thin metal film. Scientific Reports, 13(1). https://doi.org/10.1038/s41598-023-29374-6
@article{osti_1924109,
author = {Guo, Lei and Liu, Fangze and Koyama, Kazuki and Regis, Nolan and Alexander, Anna M. and Wang, Gaoxue and DeFazio, Jeffrey and Valdez, James A. and Poudel, Anju and Yamamoto, Masahiro and others},
title = {Rugged bialkali photocathodes encapsulated with graphene and thin metal film},
annote = {Abstract 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 (CsK 2 Sb)) 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 –3 Pa. In comparison, the QE decreased drastically at 10 –6 Pa for bare, non-protected CsK 2 Sb 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. },
doi = {10.1038/s41598-023-29374-6},
url = {https://www.osti.gov/biblio/1924109},
journal = {Scientific Reports},
issn = {ISSN 2045-2322},
number = {1},
volume = {13},
place = {United Kingdom},
publisher = {Nature Publishing Group},
year = {2023},
month = {02}}
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 400, Issue 1https://doi.org/10.1016/S0168-9002(97)00990-X
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 433, Issue 1-2https://doi.org/10.1016/S0168-9002(99)00358-7