A mechanism of Cu work function reduction in CsBr/Cu photocathodes

Journal Article · Mon Feb 15 00:00:00 EST 2016 · Physical Chemistry Chemical Physics. PCCP (Print)

DOI:https://doi.org/10.1039/c5cp07694c· OSTI ID:1254569

Halliday, M. T. E. ^[1]; Hess, W. P. ^[2]; Shluger, A. L. ^[1]

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1. Univ. College London, London (United Kingdom)
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Thin films of CsBr deposited on Cu(100) have been proposed as next-generation photocathode materials for applications in particle accelerators and free-electron lasers. However, the mechanisms underlying an improved photocathode performance remain poorly understood. We present density Functional Theory (DFT) calculations of the work function reduction following the application of CsBr thin film coatings to Cu photocathodes. The effects of structure and van der Waals forces are examined. Calculations suggest that CsBr films can reduce the work function by around 1.5 eV, which would explain the exponential increase in quantum efficiency (QE) of coated vs. uncoated photocathodes. In conclusion, a model explaining experimentally observed laser activation of photocathode is provided whereby the photo-induced creation of di-vacancies at the surface, and their subsequent diffusion throughout the lattice and segregation at the interface leads to a further increase in QE after a period of laser irradiation.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 1254569
• Report Number(s): PNNL-SA--114774; KC0301050
• Journal Information: Physical Chemistry Chemical Physics. PCCP (Print), Journal Name: Physical Chemistry Chemical Physics. PCCP (Print) Journal Issue: 10 Vol. 18; ISSN 1463-9076; ISSN PPCPFQ
• Publisher: Royal Society of Chemistry
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE