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

Daniel Velázquez; Rachel Seibert; Hasitha Ganegoda; Daniel Olive; Amy Rice; Kevin Logan; Zikri Yusof; Linda Spentzouris; Jeff Terry

doi:10.1016/j.apsusc.2015.11.064

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

Daniel Velázquez, Rachel Seibert, Hasitha Ganegoda, Daniel Olive, Amy Rice, Kevin Logan, Zikri Yusof, Linda Spentzouris, Jeff Terry

Research output: Contribution to journal › Article › peer-review

8 Scopus citations

Abstract

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. The reproducibility of the emission parameters under specific growth conditions is excellent, even though the interfaces themselves have varying degrees of roughness.

Original language	English
Pages (from-to)	762-766
Number of pages	5
Journal	Applied Surface Science
Volume	360
DOIs	https://doi.org/10.1016/j.apsusc.2015.11.064
State	Published - Jan 1 2016
Externally published	Yes

Funding

The authors thank the staff of AWA at ANL, Eric Wisniewski, Katherine Harkay and Károly Németh for valuable discussions and the facilitation of resources crucial for the completion of these studies. We also thank the staff of CMP and U13UB beamline from NSLS at BNL. This work was funded by the U.S. National Science Foundation under the grant no. 0969989 , the U.S. Department of Energy under the grant no. DE-SC0007952 and the U.S. Department of Education through the GAANN Fellowship Program, award no. P200A090137 .

Funders	Funder number
U.S. National Science Foundation
National Science Foundation	1535676
U.S. Department of Energy	DE-SC0007952
Directorate for Mathematical and Physical Sciences	0969989
U.S. Department of Education

Keywords

Epitaxy
Photocathode
Pulsed laser deposition
Quantum efficiency
RHEED
Work function

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10.1016/j.apsusc.2015.11.064

Cite this

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title = "Tailoring the emissive properties of photocathodes through materials engineering: Ultra-thin multilayers",

abstract = "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. N{\'e}meth 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. The reproducibility of the emission parameters under specific growth conditions is excellent, even though the interfaces themselves have varying degrees of roughness.",

keywords = "Epitaxy, Photocathode, Pulsed laser deposition, Quantum efficiency, RHEED, Work function",

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AU - Seibert, Rachel

AU - Ganegoda, Hasitha

AU - Olive, Daniel

AU - Rice, Amy

AU - Logan, Kevin

AU - Yusof, Zikri

AU - Spentzouris, Linda

AU - Terry, Jeff

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N2 - 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. The reproducibility of the emission parameters under specific growth conditions is excellent, even though the interfaces themselves have varying degrees of roughness.

AB - 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. The reproducibility of the emission parameters under specific growth conditions is excellent, even though the interfaces themselves have varying degrees of roughness.

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

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Keywords

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