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Rugged bialkali photocathodes encapsulated with graphene and thin metal film.

Authors :
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
Source :
Scientific Reports; 3/2/2023, Vol. 13 Issue 1, p1-9, 9p
Publication Year :
2023

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<subscript>2</subscript>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<superscript>–3</superscript> Pa. In comparison, the QE decreased drastically at 10<superscript>–6</superscript> Pa for bare, non-protected CsK<subscript>2</subscript>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. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
20452322
Volume :
13
Issue :
1
Database :
Complementary Index
Journal :
Scientific Reports
Publication Type :
Academic Journal
Accession number :
162207018
Full Text :
https://doi.org/10.1038/s41598-023-29374-6