Effects of Cs Coverage and O/Te Incorporation Order on the Work Function of Cs/O/Te-activated GaAs(100)

Authors

  • Chaofeng Hu "Laboratory for Ultrafast Transient Facility, Chongqing University, Chongqing 400044, China" & "College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China" Author
  • Ziyi Ran "Laboratory for Ultrafast Transient Facility, Chongqing University, Chongqing 400044, China" & "College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China" Author
  • Tao Cui "Laboratory for Ultrafast Transient Facility, Chongqing University, Chongqing 400044, China" & "College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China" Author
  • Jie Yang "Laboratory for Ultrafast Transient Facility, Chongqing University, Chongqing 400044, China" & "College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China" Author
  • Meng Li Laboratory for Ultrafast Transient Facility, Chongqing University, Chongqing 400044, China Author
  • Xiaodong Yang Laboratory for Ultrafast Transient Facility, Chongqing University, Chongqing 400044, China Author
  • Wei Liu "Laboratory for Ultrafast Transient Facility, Chongqing University, Chongqing 400044, China" & "College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China" Author

DOI:

https://doi.org/10.66000/3110-9772.2026.02.08

Keywords:

GaAs photocathode, Cs/O/Te activation, Work function, Adsorption energy, Surface dipole

Abstract

By lowering the vacuum energy level relative to the Fermi level, surface activation can reduce the work function of GaAs photocathodes, facilitating electron emission. Here, we use density functional theory to examine how Cs coverage and O/Te incorporation order affect the work function of Cs/O/Te-activated GaAs(100)-. Cs-O-Te (O-first) and Cs-Te-O (Te-first) layers were compared over coverages of 1-11 Cs atoms per surface unit cell (0.14–1.57 monolayers on the nominal scale), with Cs-O as the conventional reference. At each Cs coverage, the ternary models had identical compositions but differed in their O/Te introduction sequences and associated initial site assignments. The total adsorption energy became more negative with increasing Cs coverage, whereas the average adsorption energy per Cs atom generally became less negative. All three systems exhibited nonmonotonic work-function changes with Cs coverage. Among the sampled configurations, the lowest work functions were 1.594 eV for 5Cs-O, 1.478 eV for 4Cs-O-Te, and 1.651 eV for 7Cs-Te-O. Cs-O-Te reached its discrete minimum at a lower Cs coverage than Cs-Te-O. Classical dipole-model fits captured the overall coverage dependence. Bader analysis showed that Cs atoms lost electrons on average, whereas O gained electrons, consistent with the charge-density-difference distributions. In Cs-O-Te, Te accumulated electrons at relatively low coverage; in Cs-Te-O, Te exhibited net electron depletion at lower coverage and net electron accumulation at higher coverage. The interfacial dipole varied with coverage in a manner qualitatively consistent with the work-function reduction. The work-function and adsorption-energy trends identify O-first activation at modest Cs loading as a promising starting point for dose optimization.

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Published

2026-11-11

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Vol. 2 (2026)

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Copyright (c) 2026 Chaofeng Hu, Ziyi Ran, Tao Cui, Jie Yang, Meng Li, Xiaodong Yang, Wei Liu (Author)

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