In this paper, by using lattice-matched Strontium Titanate substrates in conjunction with co-deposition techniques, we have demonstrated the growth of a high quantum efficiency cesium antimonide film. We have measured the topographical and surface potential variations on this film and shown it to be more than 4 times smoother than the current state-of-the-art. We show that the surface non-uniformities on such a film are small enough to not have any noticeable impact on the brightness of electron beams under any realistic operation condition.  

This result advances the CBB goal of reduction of MTE and increase of electron beam brightness.

This work presents scientific advances that lie at the juncture of photocathode physics, accelerator physics and solid-state physics, and takes critical steps towards advancing real world applications like XFEL and UED. Moreover, these results will have a direct impact on the choice of the photocathode and the electron gun design of several upcoming XFEL facilities, most notably, the high energy upgrade of LCLS-II currently being developed at Stanford Linear Accelerator Center (SLAC).

In this work, we show that high QE Cs₃Sb films grown on lattice-matched Strontium Titanate (STO) substrates have a factor of 4 smoother surfaces compared to those traditionally grown on disordered Si surfaces. We perform simulations to calculate roughness induced MTE based on the 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. 

We believe that this work presents scientific advances that lie at the juncture of photocathode physics, accelerator physics and solid-state physics, and takes critical steps towards advancing real world applications like XFEL and UED. Moreover, these results will have a direct impact on the choice of the photocathode and the electron gun design of several upcoming XFEL facilities, most notably, the high energy upgrade of LCLS-II currently being developed at Stanford Linear Accelerator Center (SLAC). 

For these reasons, we believe that this work makes a significant advance in the field of electron sources and has a direct impact on real-world applications.

References:

P. Saha, O. Chubenko, G. S. Gevorkyan, A. Kachwala, C. J. Knill, C. Sarabia-Cardenas, E. Montgomery, S. Poddar, J. T. Paul, R. G. Hennig, H. A. Padmore, and S. Karkare, “Physically and chemically smooth cesium-antimonide photocathodes on single crystal strontium titanate substrates,” Appl. Phys. Lett., vol. 120, no. 19, p. 194102, May 2022, doi: 10.1063/5.0088306. [Online]. Available: https://aip.scitation.org/doi/full/10.1063/5.0088306