Tailoring the emissive properties of photocathodes through materials engineering: Ultra-thin multilayers

Journal Article · Thu Nov 12 00:00:00 EST 2015 · Applied Surface Science

DOI:https://doi.org/10.1016/j.apsusc.2015.11.064· OSTI ID:1467324

Velazquez, Daniel ^[1]; Seibert, Rachel ^[1]; Ganegoda, Hasitha ^[1]; Olive, Daniel Thomas  ^[2]; Rice, Amy ^[1]; Logan, Kevin ^[1]; Yusof, Zikri ^[1]; Spentzouris, Linda ^[1]; Terry, Jeff ^[1]

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1. Illinois Institute of Technology, Chicago, IL (United States)
2. Illinois Institute of Technology, Chicago, IL (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

In this paper, we report on an experimental verification that emission properties of photocathodes can be manipulated through the engineering of the surface electronic structure. Ultrathin multilayered MgO/Ag(0 0 1)/MgO films were grown by pulsed laser deposition, tuning the thickness n of the flanking MgO layers to 0, 2, 3, and 4 monolayers. We observed an increase in quantum efficiency and simultaneous decrease in work function with layer thickness. The scale and trend direction of measurements are in good but not excellent agreement with theory. Angle resolved photoemission data for the multilayered sample n = 3 showed that the emission profile has a metallic-like momentum dispersion. Deviations from theoretical predictions [K. Németh et al., PRL 104, 046801 (2010)] are attributed to imperfections of real surfaces in contrast with the ideal surfaces of the calculation. Photoemissive properties of cathodes are critical for electron beam applications such as photoinjectors for Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). An ideal photoemitter has a high quantum efficiency, low work function, low intrinsic emittance and long lifetime. It has been demonstrated here that emission properties may be systematically tailored by control of layer thickness in ultrathin multilayered structures. Lastly, the reproducibility of the emission parameters under specific growth conditions is excellent, even though the interfaces themselves have varying degrees of roughness.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-06NA25396; SC0007952
• OSTI ID: 1467324
• Alternate ID(s): OSTI ID: 1358799
• Report Number(s): LA-UR-17-24546
• Journal Information: Applied Surface Science, Vol. 360, Issue PB; ISSN 0169-4332
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Pulsed laser deposition
RHEED
Epitaxy
Photocathode
Work function
Quantum efficiency