Abstract
The CsK2Sb photocathode is capable of generating a high-intensity and low-emittance electron beam with visible laser light. In this study, we examined CsK2Sb photocathode evaporation on n- and p-type Si(100), GaAs(100), and Si(111) substrates, and compared their cathode performance. We found that the quantum efficiency of the p-type substrate was superior to that of the n-type substrate for the same substrate material and surface orientation. We show that this can be qualitatively analyzed by an energy-band model for the semiconductor(metal)-semiconductor junction between CsK2Sb and the substrate. We also evaporated the Cs3Sb cathode on n- and p-type Si(100) and GaAs(100) substrates, and confirmed that the cathode performance of all substrates was consistent with the model results. This finding indicates the possibility of improving the thin-film cathode performance by revisiting the semiconductor(metal)-semiconductor junction between the cathode and the substrate, which improves the understanding of high-performance photocathodes.
Highlights
Future accelerator projects based on linear accelerators, such as the Energy Recovery Linac (ERL) [1], Free Electron Laser (FEL) [2], and Linear Collider (LC) [3] will extend the knowledge base in scientific applications
To improve our understanding for the underlying physics of CsK2Sb photo-cathode, we studied the effect of the semiconductor type (p or n) of the substrates on the cathode performance
We studied the substrate dependence of the performance of the CsK2Sb photocathode by employing an evaporation process which gives high quantum efficiency (QE) with high reproducibility
Summary
Future accelerator projects based on linear accelerators, such as the Energy Recovery Linac (ERL) [1], Free Electron Laser (FEL) [2], and Linear Collider (LC) [3] will extend the knowledge base in scientific applications. It is well known that the CsK2Sb cathode performance depends on the substrate material and surface conditions [13,18,19,20,21], the underlying physics has not been extensively studied to date because of the lack of standardization of the cathode evaporation process. To improve our understanding for the underlying physics of CsK2Sb photo-cathode, we studied the effect of the semiconductor type (p or n) of the substrates on the cathode performance. For this purpose, CsK2Sb cathode was fabricated on Si(100), Si(111), and GaAs(100) of the p- and n-type with the process established in our previous study [26]
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