TY - JOUR
T1 - Physically and chemically smooth cesium-antimonide photocathodes on single crystal strontium titanate substrates
AU - Saha, Pallavi
AU - Chubenko, Oksana
AU - Gevorkyan, Gevork S.
AU - Kachwala, Alimohammed
AU - Knill, Christopher J.
AU - Sarabia-Cardenas, Carlos
AU - Montgomery, Eric
AU - Poddar, Shashi
AU - Paul, Joshua T.
AU - Hennig, Richard G.
AU - Padmore, Howard A.
AU - Karkare, Siddharth
N1 - Funding Information:
This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132—The Center for Bright Beams and the U.S. Department of Energy under Grant Nos. DE-SC0021092 and DE-SC0020575.
Publisher Copyright:
© 2022 Author(s).
PY - 2022/5/9
Y1 - 2022/5/9
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85130079038&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85130079038&partnerID=8YFLogxK
U2 - 10.1063/5.0088306
DO - 10.1063/5.0088306
M3 - Article
AN - SCOPUS:85130079038
SN - 0003-6951
VL - 120
JO - Applied Physics Letters
JF - Applied Physics Letters
IS - 19
M1 - 194102
ER -