Physically and chemically smooth cesium-antimonide photocathodes on single crystal strontium titanate substrates

Pallavi Saha, Oksana Chubenko, Gevork S. Gevorkyan, Alimohammed Kachwala, Christopher J. Knill, Carlos Sarabia-Cardenas, Eric Montgomery, Shashi Poddar, Joshua T. Paul, Richard G. Hennig, Howard A. Padmore, Siddharth Karkare

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The performance of x-ray free electron lasers and ultrafast electron diffraction experiments is largely dependent on the brightness of electron sources from photoinjectors. The maximum brightness from photoinjectors at a particular accelerating gradient is limited by the mean transverse energy (MTE) of electrons emitted from photocathodes. For high quantum efficiency (QE) cathodes like alkali-antimonide thin films, which are essential to mitigate the effects of non-linear photoemission on MTE, the smallest possible MTE and, hence, the highest possible brightness are limited by the nanoscale surface roughness and chemical inhomogeneity. In this work, we show that high QE Cs3Sb films grown on lattice-matched strontium titanate (STO) substrates have a factor of 4 smoother, chemically uniform surfaces compared to those traditionally grown on disordered Si surfaces. We perform simulations to calculate roughness induced MTE based on measured topographical and surface-potential variations on the Cs3Sb films grown on STO and show that these variations are small enough to have no consequential impact on the MTE and, hence, the brightness.

Original languageEnglish (US)
Article number194102
JournalApplied Physics Letters
Issue number19
StatePublished - May 9 2022

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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